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  SCIENTIFIC CULTURE,
  _AND OTHER ESSAYS_.

  BY
  JOSIAH PARSONS COOKE, LL. D.,
  PROFESSOR OF CHEMISTRY AND MINERALOGY, IN HARVARD COLLEGE.

  _SECOND EDITION; WITH ADDITIONS._

  NEW YORK:
  D. APPLETON AND COMPANY,
  1, 3, AND 5 BOND STREET.
  1885.



  COPYRIGHT, 1881, 1885,
  BY JOSIAH PARSONS COOKE.



  TO
  MY ASSOCIATES
  IN
  THE CHEMICAL LABORATORY
  OF
  HARVARD COLLEGE
  THIS VOLUME
  IS
  AFFECTIONATELY DEDICATED.




PREFACE.


The essays collected in this volume, although written for special
occasions without reference to each other, have all a bearing on the
subject selected as the title of the volume, and are an outcome of a
somewhat large experience in teaching physical science to college
students. Thirty years ago, when the writer began his work at Cambridge,
instruction in the experimental sciences was given in our American
colleges solely by means of lectures and recitations. Chemistry and
Physics were allowed a limited space in the college curriculum as
branches of useful knowledge, but were regarded as wholly subordinate to
the classics and mathematics as a means of education; and as physical
science was then taught, there can be no question that the accepted
opinion was correct. Experimental science can never be made of value as
a means of education unless taught by its own methods, with the one
great aim in view to train the faculties of the mind so as to enable the
educated man to read the Book of Nature for himself.

Since the period just referred to, the example early set at Cambridge of
making the student's own observations in the laboratory or cabinet the
basis of all teaching, either in experimental or natural history
science, has been generally followed. But in most centers of education
the old traditions so far survive that the great end of scientific
culture is lost in attempting to conform even laboratory instruction to
the old academic methods of recitations and examinations. These, as
usually conducted, are simply hindrances in a course of scientific
training, because they are no tests of the only ability or acquirement
which science values, and therefore set before the student a false aim.
To point out this error, and to claim for science teaching its
appropriate methods, was one object of the writer in these essays.

It is, however, too often the case that, in following out our theories
of education, we avoid Scylla only to encounter Charybdis, and so, in
specializing our courses of laboratory instruction, there is great
danger of falling into the mechanical routine of a technical art, and
losing sight of those grand ideas and generalizations which give breadth
and dignity to scientific knowledge. That these great truths are as
important an element of scientific culture as experimental skill, the
author has also endeavored to illustrate, and he has added brief notices
of the lives of two noble men of science which may add force to the
illustrations.




CONTENTS.


                                                                  PAGE
     I.--SCIENTIFIC CULTURE                                          5
    II.--THE NOBILITY OF KNOWLEDGE                                  45
   III.--THE ELEMENTARY TEACHING OF PHYSICAL SCIENCE                71
    IV.--THE RADIOMETER                                             86
     V.--MEMOIR OF THOMAS GRAHAM                                   127
    VI.--MEMOIR OF WILLIAM HALLOWES MILLER                         145
   VII.--WILLIAM BARTON ROGERS                                     160
  VIII.--JEAN-BAPTISTE-ANDRÉ DUMAS                                 181
    IX.--THE GREEK QUESTION                                        203
     X.--FURTHER REMARKS ON THE GREEK QUESTION                     214
    XI.--SCIENTIFIC CULTURE; ITS SPIRIT, ITS AIM, AND ITS METHODS  227
   XII.--"NOBLESSE OBLIGE"                                         267
  XIII.--THE SPIRITUAL LIFE                                        289




ESSAYS.




I.

SCIENTIFIC CULTURE.

    _An Address delivered July 7, 1875, at the Opening of the Summer
    Courses of Instruction in Chemistry, at Harvard University._


You have come together this morning to begin various elementary courses
of instruction in chemistry and mineralogy. As I have been informed,
most of you are teachers by profession, and your chief object is to
become acquainted with the experimental methods of teaching physical
science, and to gain the advantages in your study which the large
apparatus of this university is capable of affording.

In all this I hope you will not be disappointed. You, as teachers, know
perfectly well that success must depend, first of all, on your own
efforts; but, since the methods of studying Nature are so different from
those with which you are familiar in literary studies, I feel that the
best service I can render, in this introductory address, is to state,
as clearly as I can, the great objects which should be kept in view in
the courses on which you are now entering.

By your very attendance on these courses you have given the strongest
evidence of your appreciation of the value of chemical studies as a part
of the system of education, and let me say, in the first place, that you
have not overvalued their importance. The elementary principles and more
conspicuous facts of chemistry are so intimately associated with the
experience of every-day life, and find such important applications in
the useful arts, that no man at the present day can be regarded as
educated who is ignorant of them. Not to know why the fire burns, or how
the sulphur trade affects the industries of the world, will be regarded,
by the generation of men among whom your pupils will have to win their
places in society, as a greater mark of ignorance than a false quantity
in Latin prosody or a solecism in grammar.

Moreover, I need not tell you that physical science has become a great
power in the world. Indeed, after religion, it is the greatest power of
our modern civilization. Consider how much it has accomplished during
the last century toward increasing the comforts and enlarging the
intellectual vision of mankind. The railroad, the steamship, the
electric telegraph, photography, gaslights, petroleum oils, coal-tar
colors, chlorine bleaching, anæsthesia, are a few of its recent
material gifts to the world; and not only has it made one pair of hands
to do the work of twenty, but it has so improved and facilitated the old
industries that what were luxuries to the fathers of our republic have
become necessities to our generation.

And when, passing from these material fruits, you consider the purely
intellectual triumphs of physical science, such as those which have been
gained with the telescope, the microscope, and the spectroscope, you can
not wonder at the esteem in which these branches of study are held in
this practical age of the world.

Now, these immense results have been gained by the application to the
study of Nature of a method which was so admirably described by Lord
Bacon in his "Novum Organon," and which is now generally called the
experimental method. What we observe in Nature is an orderly succession
of phenomena. The ancients speculated about these phenomena as well as
ourselves, but they contented themselves with speculations, animating
Nature with the products of their wild fancies. Their great master,
Aristotle, has never been excelled in the art of dialectics; but his
method of logic applied to the external world was of very necessity an
utter failure. It is frequently said, in defense of the exclusive study
of the records of ancient learning, that they are the products of
thinking, loving, and hating men, like ourselves, and it is claimed that
the study of science can never rise to the same nobility because it
deals only with lifeless matter. But this is a mere play on words, a
repetition of the error of the old schoolmen.

Physical science is noble because it does deal with thought, and with
the very noblest of all thought. Nature at once manifests and conceals
an Infinite Presence: her methods and orderly successions are the
manifestations of Omnipotent Will; her contrivances and laws the
embodiment of Omniscient Thought. The disciples of Aristotle so signally
failed simply because they could see in Nature only a reflection of
their idle fancies. The followers of Bacon have so gloriously succeeded
because they approached Nature as humble students, and, having first
learned how to question her, have been content to be taught and not
sought to teach. The ancient logic never relieved a moment of pain, or
lifted an ounce of the burden of human misery. The modern logic has made
a very large share of material comfort the common heritage of all
civilized men.

In what, then, does this Baconian system consist? Simply in these
elements: 1. Careful observation of the conditions under which a given
phenomenon occurs; 2. The varying of these conditions by experiments,
and observing the effects produced by the variation. We thus find that
some of the conditions are merely accidental circumstances, having no
necessary connection with the phenomenon, while others are its
invariable antecedent. Having now discovered the true relations of the
phenomenon we are studying, a happy guess, suggested probably by
analogy, furnishes us with a clew to the real causes on which it
depends. We next test our guess by further experiments. If our
hypothesis is true, this or that must follow; and, if in all points the
theory holds, we have discovered the law of which we are in search. If,
however, these necessary inferences are not realized, then we must
abandon our hypothesis, make another guess, and test that in its turn.
Let me illustrate by two well-known examples:

The, of old, universally accepted principle that all living organisms
are propagated by seeds or germs (_omnia ex ovo_) has been seriously
questioned by a modern school of naturalists. Various observers have
maintained that there were conditions under which the lower forms of
organic life were developed independently of all such accessories, but
other, and equally competent, naturalists, who have attempted to
investigate the subject, have obtained conflicting results.

Thus it was observed that certain low forms of life were quite
constantly developed in beef juice that had been carefully prepared and
hermetically sealed in glass flasks, even after these flasks had been
exposed for a long time to the temperature of boiling water. "Here,"
proclaims the new school, "is unmistakable evidence of spontaneous
generation; for, if past experience is any guide, all germs must have
been killed by the boiling water." "No," answer the more cautious
naturalists, "you have not yet proved your point. You have no right to
assume that all germs are killed at this temperature."

The experiments, therefore, were repeated under various conditions and
at different temperatures, but with unsatisfactory results, until
Pasteur, a distinguished French physicist, devised a very simple mode of
testing the question. He reasoned thus: "If, as is generally believed,
the presence of invisible spores in the air is an essential condition of
the development of these lower growths, then their production must bear
some proportion to the abundance of these spores. Near the habitations
of animals and plants, where the spores are known to be in abundance,
the development would be naturally at a maximum, and we should expect
that the growth would diminish in proportion as the microscope indicated
that the spores diminished in the atmosphere."

Accordingly, Pasteur selected a region in the Jura Mountains suitable
for his purpose, and repeated the well-known experiment with beef juice,
first at the inn of a town at the foot of the mountains, and then at
various elevations up to the bare rocks which covered the top of the
ridge, a height of some eight thousand feet. At each point he sealed up
beef juice in a large number of flasks, and watched the result. He found
that while in the town the animalcules were developed in almost all the
flasks, they appeared only in two or three out of a hundred cases where
the flasks had been sealed at the top of the mountain, and to a
proportionate extent in those sealed at the intermediate elevations.
What, now, did these experiments prove? Simply this, that the
development of these organic forms was in direct proportion to the
number of germs in the air. It did not settle the question of
spontaneous generation, but it showed that false conclusions had been
deduced from the experiments which had been cited to prove it.

A still more striking illustration of the same method of questioning
Nature is to be found in the investigation of Sir Humphry Davy, on the
composition of water. The voltaic battery which works our telegraphs was
invented by Volta in 1800; and later, during the same year, it was
discovered in London, by Nicholson and Carlisle, that this remarkable
instrument had the power of decomposing water. These physicists at once
recognized that the chief products of the action of the battery on water
were hydrogen and oxygen gases, thus confirming the results of
Cavendish, who, in 1781, had obtained water by combining these
elementary substances; oxygen having been previously discovered in 1775,
and hydrogen, at least, as early as 1766. It was, however, very soon
also observed that there were always formed by the action of the battery
on water, besides these aëriform products, an alkali and an acid, the
alkali collecting around the negative pole, and the acid around the
positive pole of the electrical combination. In regard to the nature of
this acid and alkali, there was the greatest difference of opinion among
the early experimenters on this subject. Cruickshanks supposed that the
acid was nitrous acid, and the alkali ammonia. Desormes, a French
chemist, attempted to prove that the acid was muriatic acid; while
Brugnatelli asserted that a new and peculiar acid was formed, which he
called the electric acid.

It was in this state of the question that Sir Humphry Davy began his
investigation. From the analogies of chemical science, as well as from
the previous experiments of Cavendish and Lavoisier, he was persuaded
that water consisted solely of oxygen and hydrogen gases, and that the
acid and alkali were merely adventitious products. This opinion was
undoubtedly well founded; but, great disciple of Bacon as he was, Davy
felt that his opinion was worth nothing unless substantiated by
experimental evidence, and accordingly he set himself to work to obtain
the required proof.

In Davy's first experiments the two glass tubes which he used to contain
the water were connected together by an animal membrane, and he found,
on immersing the poles of his battery in their respective tubes, that,
besides the now well-known gases, there were really formed muriatic acid
in one tube, and a fixed alkali in the other. Davy at once, however,
suspected that the acid and alkali came from common salt contained in
the animal membrane, and he therefore rejected this material and
connected the glass tubes by carefully washed cotton fiber, when, on
submitting the water as before to the action of the voltaic current, and
continuing the experiment through a great length of time, no _muriatic_
acid appeared; but he still found that the water in the one tube was
strongly alkaline, and in the other strongly acid, although the acid was
chiefly, at least, nitrous acid. A part of the acid evidently came from
the animal membrane, but not the whole, and the source of the alkali was
as obscure as before.

Davy then made another guess. He knew that alkali was used in the
manufacture of glass; and it occurred to him that the glass of the
tubes, decomposed by the electric current, might be the origin of the
alkali in his experiments. He therefore substituted for the glass tubes
cups of agate, which contains no alkali, and repeated the experiment,
but still the troublesome acid and alkali appeared. Nevertheless, he
said, it is possible that these products may be derived from some
impurities existing in the agate cups, or adhering to them; and so, in
order to make his experiments as refined as possible, he rejected the
agate vessels and procured two conical cups of pure gold, but, on
repeating the experiments, the acid and alkali again appeared.

And now let me ask who is there of us who would not have concluded at
this stage of the inquiry that the acid and alkali were essential
products of the decomposition of water? But not so with Davy. He knew
perfectly well that all the circumstances of his experiments had not
been tested, and until this had been done he had no right to draw such a
conclusion. He next turned to the water he was using. It was distilled
water, which he supposed to be pure, but still, he said, it is possible
that the impurities of the spring-water may be carried over to a slight
extent by the steam in the process of distillation, and may therefore
exist in my distilled water to a sufficient amount to have caused the
difficulty. Accordingly, he evaporated a quart of this water in a silver
dish, and obtained seven-tenths of a grain of dry residue. He then added
this residue to the small amount of water in the gold cones and again
repeated the experiment. The proportion of alkali and acid was sensibly
increased.

You think he has found at last the source of the acid and alkali in the
impurities of the water. So thought Davy, but he was too faithful a
disciple of Bacon to leave this legitimate inference unverified.
Accordingly, he repeatedly distilled the water from a silver alembic
until it left absolutely no residue on evaporation, and then with water
which he knew to be pure, and contained in vessels of gold from which he
knew it could acquire no taint, he still again repeated the already
well-tried experiment. He dipped his test-paper into the vessel
connected with the positive pole, and the water was still decidedly
acid. He dipped the paper into the vessel connected with the negative
pole, and the water was still alkaline.

You might well think that Davy would have been discouraged here. But not
in the least. The path to the great truths which Nature hides often
leads through a far denser and a more bewildering forest than this; but
then there is not infrequently a "blaze" on the trees which points out
the way, although it may require a sharp eye in a clear head to see the
marks. And Davy was well enough trained to observe a circumstance which
showed that he was now on the right path and heading straight for the
goal.

On examining the alkali formed in this last experiment, he found that
it was not, as before, a fixed alkali, soda or potash, but the volatile
alkali ammonia. Evidently the fixed alkali came from the impurities of
the water, and when, on repeating the experiment with pure water in
agate cups or glass tubes, the same results followed, he felt assured
that so much at least had been established. There was still, however,
the production of the volatile alkali and of nitrous acid to be
accounted for. As these contain only the elements of air and water, Davy
thought that possibly they might be formed by the combination of
hydrogen at the one pole and of oxygen at the other with the nitrogen of
the air, which was necessarily dissolved in the water. In order,
therefore, to eliminate the effect of the air, he again repeated the
experiment under the receiver of an air-pump from which the atmosphere
had been exhausted, but still the acid and alkali appeared in the two
cups.

Davy, however, was not discouraged by this, for the "blazes" on the
trees were becoming more numerous, and he now felt sure that he was fast
approaching the end. He observed that the quantity of acid and alkali
had been greatly diminished by exhausting the air, and this was all that
could be expected, for, as Davy knew perfectly well, the best air-pumps
do not remove all the air. He therefore, for the last experiment, not
only exhausted the air, but replaced it with pure hydrogen, and then
exhausted the hydrogen and refilled the receiver with the same gas
several times in succession, until he was perfectly sure that the last
traces of air had been as it were washed out. In this atmosphere of pure
hydrogen he allowed the battery to act on the water, and not until the
end of twenty-four hours did he disconnect the apparatus. He then dips
his test-paper into the water connected with the positive pole, and
there is no trace of acid; he dips it into the water at the negative
pole, and there is no alkali; and you may judge with what satisfaction
he withdraws those slips of test-paper, whose unaltered surfaces showed
that he had been guided at last to the truth, and that his perseverance
had been rewarded.

The fame of Sir Humphry Davy rests on his discovery of the metals of the
alkalies and earths which first revealed the wonderful truth that the
crust of our globe consists of metallic cinders; but none of these
brilliant results show so great scientific merit or such eminent power
of investigating Nature as the experiments which I have just detailed. I
have not, however, described them here for the purpose of glorifying
that renowned man. His honored memory needs no such office at my hands.
My only object was to show you what is meant by the Baconian method of
science, and to give some idea of the nature of that modern logic which
within the last fifty years has produced more wonderful transformations
in human society than the author of Aladdin ever imagined in his wildest
dreams. In this short address I can of course give you but a very dim
and imperfect idea of what I have called the Baconian system of
experimental reasoning. Indeed, you can not form any clear conception of
it, until in some humble way you have attempted to use the method, each
one for himself, and you have come here in order that you may acquire
such experience.

My object, however, will be gained if these illustrations serve to give
emphasis to the following statements, which I feel I ought to make at
the opening of these courses of instruction--statements which have an
especial appropriateness in this place, since I am addressing teachers,
who are in a position to exert an important influence on the system of
education in this country.

In the first place, then, I must declare my conviction that no educated
man can expect to realize his best possibilities of usefulness without a
practical knowledge of the methods of experimental science. If he is to
be a physician, his whole success will depend on the skill with which he
can use these great tools of modern civilization. If he is to be a
lawyer, his advancement will in no small measure be determined by the
acuteness with which he can criticise the manner in which the same tools
have been used by his own or his opponent's clients. If he is to be a
clergyman, he must take sides in the great conflict between theology and
science which is now raging in the world, and, unless he wishes to play
the part of the doughty knight Don Quixote, and think he is winning
great victories by knocking down the imaginary adversaries which his
ignorance has set up, he must try the steel of his adversary's blade.

Let me be fully understood. It is not to be expected or desired that
many of our students should become professional men of science. The
places of employment for scientific men are but few, and more in the
future than in the past they will naturally be secured by those whom
Nature has endowed with special aptitudes or tastes--usually the signs
of aptitudes--to investigate her laws. That our country will always
offer an honorable career to her men of genius, we have every reason to
expect, and these born students of Nature will usually follow the plain
indications of Providence without encouragement or direction from us.

It is different, however, with the great body of earnest students who
are conscious of no special aptitudes, but who are desirous of doing the
best thing to fit themselves for usefulness in the world; and I feel
that any system of education is radically defective which does not
comprise a sufficient training in the methods of experimental science
to make the mass of our educated men familiar with this tool of modern
civilization: so that, when, hereafter, new conquests over matter are
announced and great discoveries are proclaimed, they may be able not
only to understand but also to criticise the methods by which the
assumed results have been reached, and thus be in a position to
distinguish between the true and the false. Whether we will or not, we
must live under the direction of this great power of modern society, and
the only question is whether we will be its ignorant slave or its
intelligent servant.

In the second place, it seems fitting that I should state to you what I
regard as the true aims to be kept in view in a course of scientific
study, and to give my reasons for the methods we have adopted in
arranging the courses you are about beginning.

In our day there has arisen a warm discussion as to the relative claims
of two kinds of culture, and attempts are made to create an antagonism
between them. But all culture is the same in spirit. Its object is to
awaken and strengthen the powers of the mind; for these, like the
muscles of the body, are developed and rendered strong and active only
by exercise; while, on the other hand, they may become atrophied from
mere want of use. Science culture differs in its methods from the old
classical culture, but it has the same spirit and the same object. You
must not, therefore, expect me to advocate the former at the expense of
the latter; for, although I have labored assiduously during a quarter of
a century to establish the methods of science teaching which have now
become general, I am far from believing that they are the only true
modes of obtaining a liberal education. So far from this, if it were
necessary to choose one of two systems, I should favor the classical;
and why?

Language is the medium of thought, and can not be separated from it. He
who would think well must have a good command of language, and he who
has the best command of language I am almost tempted to say will think
the best. For this reason a certain amount of critical study of language
is essential for every educated man, and such study is not likely to be
gained except through the great ancient languages; the advocates of
classical scholarship frequently say, can not be gained. I am not ready
to accept this dictum; but I most willingly concede that in the present
state of our schools it is not likely to be gained. I never had any
taste myself for classical studies; but I know that I owe to the study a
great part of the mental culture which has enabled me to do the work
that has fallen to my share in life.

But, while I concede all this, I do not believe, on the other hand, that
the classical is the only effective method of culture; you evidently do
not think so, for you would not be here if you did. But, in abandoning
the old tried method, which is known to be good, for the new, you must
be careful that you gain the advantages which the new offers; and you
will not gain the new culture you seek unless you study science in the
right way. In the classical departments the methods are so well
established, and have been so long tested by experience, that there can
hardly be a wrong way. But in science there is not only a wrong way, but
this wrong way is so easy and alluring that you will most certainly
stray into it unless you strive earnestly to keep out of it. Hence I am
most anxious to point out to you the right way, and do what I can to
keep you in it; and you will find that our courses and methods have been
devised with this object.

When advocating in our mother University of Cambridge, in Old England,
the claims of scientific culture, I was pushed with an argument which
had very great weight with the eminent English scholars present, and
which you will be surprised to learn was regarded as fatal to the
success of the science "triposes" then under debate. The argument was
that the experimental sciences could not be made the subjects of
competitive examinations. Some may smile at such an objection; but, as
viewed from the English standpoint, there was really a great deal in it,
and the argument brought out the radical difference between scientific
and classical culture.

The old method of culture may be said to have culminated in the
competitive examinations of the English universities. We have no such
examinations here. Success depends not simply on knowing your subject
thoroughly, but on having it at your fingers' ends, and those fingers so
agile that they can accomplish not only a prodigious amount of work in a
short time, but can do this work with absolute accuracy. For the only
approach we make to an experience of this kind, we must look to our
athletic contests. It may of course be doubted whether the ability, once
in a man's life, to perform such mental feats, is worth what it costs.
Still it implies a very high degree of mental culture, and it is
perfectly certain that the experimental sciences give no field for that
sort of mental prize-fights. It is easy to prepare written examinations
which will show whether the students have been faithful to their work,
but they can not be adapted to such competitions as I have described
without abandoning the true object of science culture. The ability of
the scientific student can only be shown by long-continued work at the
laboratory table, and by his success in investigating the problems which
Nature presents.

We have here struck the true key-note of the scientific method. The
great object of all our study should be to study Nature, and all our
methods should be directed to this one object. This aim alone will
ennoble our scholarship as students, and will give dignity to our
scientific calling as men of science. It is this high aim, moreover,
which vindicates the worth of the mode of culture we have chosen. What
is it that ennobles literary culture but the great minds which, through
this culture, have honored the nations to which they belong?

The culture we have chosen is capable of even greater things; not
because science is nobler than art, for both are equally noble--it is
the thought, the conception, which ennobles, and I care not whether it
be attained through one kind of exercise of the mental faculties or
another--but we are capable of grander and nobler thoughts than Plato,
Cicero, Shakespeare, or Newton, because we live in a later period of the
world's history, when, through science, the world has become richer in
great ideas. It is, I repeat, the great thought which ennobles, and it
ennobles because it raises to a higher plane that which is immortal in
our manhood.

If I have made my meaning clear, and if you sympathize with my feelings,
you will understand why I regard culture as so important to the
individual and to the nation. The works of Shakespeare and of Bacon are
of more value to England to-day than the memories of Blenheim or
Trafalgar; and those great minds will still be living powers in the
world when Marlborough and Nelson are only remembered as historical
names.

I therefore believe that it is the first duty of a country to foster the
highest culture, and that it should be the aim of every scholar to
promote this culture both by his own efforts and his active influence. A
nation can become really great in no other way. We live in a country of
great possibilities; and the danger is that, as with many men I have
known in college, of great potential abilities, the greatness will end
where it begins. The scholars of the country should have but one voice
in this matter, and urge upon the government and upon individuals the
duty of encouraging and supporting mental culture for its own sake.

The time has passed when we can afford to limit the work of our higher
institutions of learning to teaching knowledge already acquired.
Henceforth the investigation of unsolved problems, and the discovery of
new truth, should be one of the main objects at our American
universities, and no cost grudged which is required to maintain at them
the most active minds, in every branch of knowledge which the country
can be stimulated to produce.

I could urge this on the self-interest of the nation as an obvious
dictate of political economy. I could say, and say truly, that the
culture of science will help us to develop those latent resources of
which we are so proud; will enable us to grow two blades of grass where
one grew before; to extract a larger percentage of metal from our ores;
to economize our coal, and in general to direct our waiting energies so
that they may produce a more abundant pecuniary reward. I could tell of
Galvani studying for twenty long years, to no apparent purpose, the
twitching of frogs' hind-legs, and thus sowing the seed from which has
sprung the greatest invention of modern times. Or, if our Yankee
impatience would be unwilling to wait half a century for the fruit to
ripen, I could point to the purely theoretical investigations of organic
chemistry, which in less than five years have revolutionized one of the
great industries of Europe, and liberated thousands of acres for a more
beneficent agriculture. This is all true, and may be urged properly if
higher considerations will not prevail. It is an argument I have used in
other places, but I will not use it here; although I gladly acknowledge
the Providence which brings at last even material fruits to reward
conscientious labor for the advancement of knowledge and the
intellectual elevation of mankind. I would rather point to that far
greater multitude who worked in faith for the love of knowledge, and who
ennobled themselves and ennobled their nation, not because they added to
its material prosperity, but because they made themselves and made their
fellows more noble men.

I come back now again to the moral of all this, to urge upon you, as
the noblest patriotism and the most enlightened self-interest, the duty
of striving for yourselves and encouraging in others the highest culture
in the studies you have chosen, and this culture with one end in view,
to advance knowledge. I am far, of course, from advising you to grapple
immaturely with unsolved problems, or, when you have gained the
knowledge with which you can dare to venture from the beaten track, to
undertake work beyond your power. Many a young scientific man has
suffered the fate of Icarus in attempting to soar too high. Moreover, I
am far from expecting that all or many of you will ever have the
opportunity of going beyond the well-explored fields of knowledge; but
you can all have the aim, and that aim will make your work more worthy
and more profitable to yourselves. Every American boy can not be
President of the United States, but if, as our English cousins allege,
he believes that he can be, the very belief makes him an abler man.

We have dwelt long enough on these generalities, and it is time to come
down to commonplaces, and to inquire what are the essential conditions
of this scientific culture which shall fit us to investigate Nature; and
the first thought that occurs to me in this connection may be expressed
thus: Science presents to us two aspects, which I may call its objective
and its subjective aspect. Objectively it is a body of facts, which we
have to observe, and subjectively it is a body of truths, conclusions,
or inferences, deduced from these facts; and the two sides of the
subject should always be kept in view.

I propose next to say a few words in regard to each of these two aspects
of our study, and in regard to the best means of training our faculties
so as to work successfully in each sphere. First, then, success in the
observation of phenomena implies three qualities at least, namely,
quickness and sharpness of perception, accuracy in details, and
truthfulness; and on its power to cultivate these qualities a large part
of the value of science, as a means of education, depends.

To begin with the cultivation of our perceptions. We are all gifted with
senses, but how few of us use them to the best advantage! "We have eyes
and see not"; for, although the light paints the picture on the retina,
our dull perceptions give no attention to the details, and we retain
only a confused impression of what has passed before our eyes. "But
how," you may ask, "are we to cultivate this sharpness of perception?" I
answer, only by making a conscious effort to fix our attention on the
objects we study until the habit becomes a second nature. I have often
noticed, with surprise, the power which uneducated miners frequently
possess of recognizing many minerals at sight. This they have acquired
by long experience and close familiarity with such objects, and such
power of observation is with them so purely a habit that they are
frequently unable to state clearly the grounds on which their
conclusions are based. They recognize the minerals by what in common
language is called their "looks" and they notice delicate differences in
the "looks" to which most men are blind. It is, however, the business of
the scientific mineralogist to analyze these "looks," and to point out
in what the differences consist; so that by fixing his attention on
these points the student may gain, by a few hours' study, the power
which the miner acquires only after long experience.

The chief difficulty, however, which we find in teaching mineralogy is,
that the students do not readily see the differences when they are
pointed out, or, if they see them, do not remember them with sufficient
precision to render their subsequent observations conclusive and
precise. This either arises from a failure to cultivate the powers of
observation in childhood, or the subsequent blunting of them by disuse.
The ladies will scout the idea that a brooch of cut-glass is as
ornamental as one of diamond, and yet I venture to assert that there is
not one person in fifty, at least of those who have not made a study of
the subject, who can tell the difference between the two. The external
appearance depends simply on what we call lustre. The lustre of glass
is vitreous, that of the diamond adamantine; and I know of no other
distinction which it is more difficult for students to recognize than
this. Those of you who study mineralogy will experience this difficulty,
and it can be overcome only by giving careful attention to the subject.
The teacher can do nothing more than put in your hands the specimens
which illustrate the point, and you must study these specimens until you
see the difference. It is a question of sight, not of understanding, and
all the optical theories of the cause of the lustre will not help you in
the least toward seeing the difference between diamond and glass, or
anglesite and heavy spar.

Another illustration of the same fact is the constant failure of
students to distinguish by the eye alone between the two minerals called
copper-glance and gray copper. There is a difference of color and lustre
which, although usually well marked, it requires an educated eye to
distinguish.

Mineralogy undoubtedly demands a more careful cultivation of the
perceptions than the other branches of chemistry; but still you will
find abundant practice for close observation in them all. I have often
known students to reach erroneous results in qualitative analysis by
mistaking a white precipitate in a colored liquid for a colored
precipitate, or by not attending to similar broad distinctions, which
would have been obvious to any careful observer; and so in quantitative
analysis, mere delicacy of touch or handling is a great element of
success.

But I must pass on to speak of the importance in the study of Nature of
accuracy in detail, which is the second condition of successful
observation of which I spoke. We must cultivate not only accuracy in
observing details, but also accuracy in following details which have
been laid down by others for our guidance. In science we can not draw
correct conclusions from our premises unless we are sure that we have
all the facts, and what seemed at first an unimportant detail often
proves to be the determining condition of the result; and, again, if we
are told that under certain conditions a certain sign is the proof of
the presence of a certain substance, we have no right to assume that the
sign is of any value unless the conditions are fulfilled. A black
precipitate, for example, obtained under certain conditions, is a proof
of the presence of nickel, but we can not assert that we have found
nickel unless we have followed out those details in every particular.

Of course, we must avoid empiricism as far as we can. We must seek to
learn the reasons of the details, and such knowledge will not only
render our work intelligent, but will also frequently enable us to
judge how far the details are essential, and to what extent our
processes may be varied with safety. We must also avoid trifling, and,
above all, "the straining at a gnat and swallowing a camel," as is the
habit with triflers. Large knowledge and good judgment will avoid all
such errors; but, if we must choose between fussiness and carelessness,
the first is the least evil. Slovenly work means slovenly results, and
habits of carefulness, neatness, and order produce as excellent fruits
in the laboratory as in the home.

Last in order but first in importance of the conditions of successful
observation, mentioned above, stands truthfulness. Here you may think I
am approaching a delicate subject, of which even to speak might seem to
cast a reproach. But not so at all. I am not speaking here of conscious
deception, for I assume that no one who aspires to be a student of
Nature can be guilty of that. But I am speaking of a quality whose
absence is not necessarily a mark of sinfulness, but whose possession,
in a high degree, is a characteristic of the greatest scientific talent.
As every lawyer knows, he is a rare man whose testimony is not colored
by his interests, and a very large amount of self-deception is
compatible with conscious honesty of purpose.

So among scientific students the power to keep the mind unbiased, and
not to color our observations in the least degree, is one of the rarest
as it is one of the noblest of qualities. It is a quality we must strive
after with all our might, and we shall not attain it unless we strive.
Remember, our observations are our data, and, unless accurate,
everything deduced from them must have the taint of our deception. We
can not deceive Nature, however much we may deceive ourselves; and there
is many a student who would cut off his right hand rather than be guilty
of a conscious untruth, who is yet constantly untruthful to himself.
Every year students of mineralogy present to me written descriptions of
mineral specimens which particularize, as observed, characters that do
not appear on the specimen given them to determine, although they may be
the correct characters of some other mineral.

There is usually no want of honesty in this, but, deceived by some
accident, the student has made a wrong guess, and then imagined that he
saw on the specimen those characters which he knew from the descriptions
ought to appear on the assumed mineral. So, also, it not unfrequently
happens that a student in qualitative analysis, who has obtained some
hints in regard to the composition of his solution, will torture his
observations until they seem to him to confirm his erroneous inferences;
and again the student in quantitative analysis, who finds out the exact
weight he ought to obtain, is often insensibly influenced by this
knowledge--in the washing and ignition of his precipitate, or in some
other way--and thus obtains results whose only apparent fault may be a
too close agreement with theory, but which, nevertheless, are not
accurate because not true. It is evident how fatal such faults as these
must be to the investigation of truth, and they are equally destructive
of all scientific scholarship. Their effect on the student is so marked
that, although he may deceive himself, he will rarely deceive his
teacher. That he should lose confidence in his own results is, to the
teacher, one of the most marked indications of such false methods of
study, but the student usually refers his want of success to any cause
but the real one--his own untruthfulness. He will complain of the
teacher, or of the methods of instruction, and may even persuade himself
that all scientific results are as uncertain as his own. As I have said,
mere ordinary truthfulness, which spurns any conscious deception, will
not save us from falling into such faults. Our scientific study demands
a much higher order of truthfulness than this. We should so love the
truth above all price as to strive for it with single-hearted and
unswerving purpose. We must be constantly on our guard to avoid any
circumstance which would tend to bias our minds or warp our judgments,
and we must make the attainment of the truth our sole motive, guide, and
end.

It remains for me, before closing this address, to say a few words on
what I have called the subjective aspect of scientific study. Science
offers us not only a mass of phenomena to be observed, but also a body
of truths which have been deduced from these observations; and, without
the power of drawing correct inferences from the data acquired, exact
observations would be of little value. I have already described the
inductive method of reasoning, and illustrated it by two noteworthy
examples, and, in a humbler measure, we must apply the same method in
our daily work in the laboratory. We must learn how to vary our
experiments so as to eliminate the accidental circumstances, and make
evident the essential conditions of the phenomena we are studying. Such
power can only be acquired by practice, and a somewhat long experience
in active teaching has convinced me that there is no better means of
training this logical faculty than the study of qualitative chemical
analysis in which many of you are to engage.

The results of the processes of qualitative analysis are perfectly
definite and trustworthy; but they are only reached by following out the
indications of experiments which are frequently obscure, and even
apparently contradictory; reconciling by new experiments the seeming
discrepancies, and, at last, having eliminated all other possible causes
of the phenomena observed, discovering the true nature of the
substances under examination.

The study of mineralogy affords an almost equally good practice,
although in a somewhat different form. By comparing carefully many
specimens of the same mineral, you learn to distinguish the accidental
from the essential characters, and on this distinction you must base
your inferences in regard to the nature of the specimens you may be
called upon to determine. A single remark occurs to me which may aid you
in cultivating this scientific logic.

Do not attempt to reason on insufficient data. Multiply your
observations or experiments, and when your premises are ample, the
conclusion will generally take care of itself. Are you in doubt in
regard to a mineral specimen? Repeat your observations again and again,
multiply them with the aid of the blow-pipe or goniometer, compare the
specimen with known specimens which it resembles, until either your
doubts are removed or you are satisfied that you are unequal to the
task; and remember that, in many cases, the last is the only honest
conclusion.

Are you in doubt in regard to the reactions of the substance you are
analyzing, whether they are really those of a metal you suspect to be
present? Do not rest in such a frame of mind, and, above all, do not try
to remove the doubt by comparing your experience with that of your
neighbor, but multiply your own experiments; procure some compound of
the metal, and compare its reactions with those you have observed until
you reach either a positive or a negative result.

Remember that the way to remove your doubts is to widen your own
knowledge, and not to depend on the knowledge of others. When your
knowledge of the facts is ample, your inferences will be satisfactory,
and then an unexplained phenomenon is the guide to a new discovery. Do
not be discouraged if you have to labor long in the dark before the day
begins to dawn. It will at last dawn to you, as it has dawned to others
before, and, when the morning breaks, you will be satisfied with the
result of your labor.

Moreover, I feel confident that such experience will very greatly tend
to increase your appreciation of the value of scientific studies in
training the reasoning faculties of the mind. This, as every one must
admit, is the best test of their utility in a scheme of education, and
it is precisely here that I claim for them the very highest place. It
has generally been admitted that mathematical studies are peculiarly
well adapted to train the logical faculties, but still many persons have
maintained that, since the mathematics deal wholly with absolute
certainties, an exclusive devotion to this class of subjects unfits the
mind for weighing the probable evidence by which men are chiefly guided
in the affairs of life.

But, without attempting to discuss this question, on which much might be
said on both sides, it is certain that no such objection can be urged
against the study of the physical sciences if conducted in the manner I
have attempted to describe. These subjects present to the consideration
of the student every degree of probable evidence, accustoming him to
weigh all the evidence for or against a given conclusion, and to reject
or to provisionally accept only on the balance of probabilities.
Moreover, in practical science, the student is taught to follow out a
chain of probable evidence with care and caution, to eliminate all
accidental phenomena, and supply, by experiment or observation, the
missing links, until he reaches the final conclusion--an intellectual
process which, though based wholly on probable evidence, may have all
the force and certainty of a mathematical demonstration.

Indeed, that highly valued scientific acumen and skill which enables the
student to brush away the accidental circumstances by which the laws of
Nature are always concealed until the truth stands out in bold relief,
is but a higher phase of the same talent which marks professional skill
in all the higher walks of life. The physician who looks through the
external symptoms of his patient to the real disease which lurks
beneath; the lawyer, who disentangles a mass of conflicting testimony,
and follows out the truth successfully to the end; the statesman, who
sees beneath the froth of political life the great fundamental
principles which will inevitably rule the conduct of the state, and thus
foresees and provides for the coming change; the general, who discovers
amid the confusion of the battlefield the weak point of his enemy's
front; the merchant, even, who can interpret the signs of the unsettled
market--employ the same faculty, and frequently in not a much lower
degree, that discovered the law of gravitation, and which, since the
days of Newton, has worked so successfully to unveil the mysteries of
the material creation.

Moreover, I hope, my friends, that you will come to value scientific
studies, not simply because they cultivate the perceptive and reasoning
faculties, but also because they fill the mind with lofty ideals,
elevated conceptions, and noble thoughts. Indeed, I claim that there is
no better school in which to train the æsthetical faculties of the mind,
the tastes, and the imagination, than the study of natural science.

The beauty of Nature is infinite, and the more we study her works the
more her loveliness unfolds. The upheaved mountain, with its mantle of
eternal snow; the majestic cataract, with its whirl and roar of waters;
the sunset cloud, with its blending of gorgeous hues, lose nothing of
their beauty for him who knows the mystery they conceal. On the
contrary, they become, one and all, irradiated by the Infinite Presence
which shines through them, and fill the mind with grander conceptions
and nobler ideas than your uneducated child of Nature could ever attain.

Remember that I am not recommending an exclusive devotion to the natural
sciences. I am only claiming for them their proper place in the scheme
of education, and I do not, of course, deny the unquestionable value of
both the ancient and the modern classics in cultivating a pure and
elevated taste. But I do say that the poet-laureate of England has drawn
a deeper inspiration from Nature interpreted by science than any of his
predecessors of the classical school; and I do also affirm that the
pre-Raphaelite school of painting, with all its grotesque mimicry of
Nature, embodies a truer and purer ideal than that of any Roman fable or
Grecian dream.

And what shall we say of the imagination? Where can you find a wider
field for its exercise than that opened by the discoveries of modern
science? And as the mind wanders over the vast expanse, crossing
boundless spaces, dwelling in illimitable time, witnessing the displays
of immeasurable power, and studying the adaptations of Omniscient
skill, it lives in a realm of beauty, of wonder, and of awe, such as no
artist has ever attained to in word, in sound, in color, or in form. And
if such a life does not lead man to feel his own dependence, to yearn
toward the Infinite Father, and to rest on the bosom of Infinite Love,
it is simply because it is not the noble in intellect, not the great in
talent, not the profound in knowledge, not the rich in experience, not
the lofty in aspiration, not the gifted in imagery, but solely the pure
in heart, who see God.

Such, then, is a very imperfect presentation of what I believe to be the
value of scientific studies as a means of education. In what I have
stated I have implied that, for these studies to be of any real value,
the end must be constantly kept in view, and everything made subservient
to the one great object.

To study the natural sciences merely as a collection of interesting
facts which it is well for every educated man to know, seldom serves a
useful purpose. The young mind becomes wearied with the details, and
soon forgets what it has never more than half acquired. The lessons
become an exercise of the memory and of nothing more; and if, as is too
frequently the case, an attempt is made to cram the half-formed mind in
a single school-year with an epitome of half the natural
sciences--natural philosophy, astronomy, and chemistry, physiology,
zoölogy, botany, and mineralogy, following each other in rapid
succession--these studies become a great evil, an actual nuisance, which
I should be the first to vote to abate. The tone of mind is not only not
improved, but seriously impaired, and the best product is a superficial,
smattering smartness, which is the crying evil not only of our schools
but also of our country.

In order that the sciences should be of value in our educational system,
they must be taught more from things than from books, and never from
books without the things. They must be taught, also, by real living
teachers, who are themselves interested in what they teach, are
interested also in their pupils, and understand how to direct them
aright. Above all, the teachers must see to it that their pupils study
with the understanding, and not solely with the memory, not permitting a
single lesson to be recited which is not thoroughly understood, taking
the greatest care not to load the memory with any useless lumber, and
eschewing merely memorized rules as they would deadly poison. The great
difficulty against which the teachers of natural science have to contend
in the colleges are the wretched tread-mill habits the students bring
with them from the schools. Allow our students to memorize their
lessons, and they will appear respectably well, but you might as easily
remove a mountain as to make many of them think. They will solve an
involved equation of algebra readily enough so long as they can do it by
turning their mental crank, when they will break down on the simplest
practical problem of arithmetic which requires of them only thought
enough to decide whether they shall multiply or divide.

Many a boy of good capabilities has been irretrievably ruined, as a
scholar, by being compelled to learn the Latin grammar by rote at an age
when he was incapable of understanding it; and I fear that schools may
still be found where young minds are tortured by this stupefying
exercise. Those of us who have faith in the educational value of
scientific studies are most anxious that the students who resort to our
colleges should be as well fitted in the physical sciences as in the
classics, for otherwise the best results of scientific culture can not
be expected. As it is, our students come to the university, not only
with no preparation in physical science, but with their perceptive and
reasoning faculties so undeveloped that the acquisition of the
elementary principles of science is burdensome and distasteful; and good
scholars, who are ambitious of distinction, can more readily win their
laurels on the old familiar track than on an untried course of which
they know nothing, and for which they must begin their training anew.

We have improved our system of instruction in the college as fast as we
could obtain the means, but we are persuaded that the best results can
not be reached without the coöperation of the schools. We feel,
therefore, that it is incumbent upon us, in the first place, to do
everything in our power to prove to the teachers of this country how
great is the educational value of the physical sciences, when properly
taught; and secondly, to aid them in acquiring the best methods of
teaching these subjects. It is with such aims that our summer courses
have been instituted, and your presence here in such numbers is the best
evidence that they have met a real want of the community. We welcome you
to the university and to such advantages as it can afford, and we shall
do all in our power to render your brief residence here fruitful, both
in experience and in knowledge; hoping, also, that the university may
become to you, as she has to so many others, a bright light shining
calmly over the troubled sea of active life, ever suggesting lofty
thoughts, encouraging noble endeavors, and inciting all her children to
work together toward those great ends, the advancement of knowledge and
the education of mankind.




II.

THE NOBILITY OF KNOWLEDGE.

    _An Address delivered before the Free Institute at Worcester,
    Massachusetts, July 28, 1874._


Within a comparatively few years schools for the instruction of artisans
have become a prominent feature in the educational systems both of this
country and of Europe, and seem destined to supersede the old system of
apprenticeships. The establishment of these schools has been an
important step in human progress, not because any great advantage has
been gained in the cultivation of mechanical skill, but because here the
future mechanic acquires culture of the mind as well as skill of the
hand. Indeed, it may be doubted whether our utilitarian age can ever
successfully compete with those "elder days of art" when

  "Builders wrought with greatest care
  Each minute and unseen part."

But, if our industrial schools do not make better mechanics than the
workshops of the olden time, they certainly educate better men, and, by
adding to skill, knowledge, they are elevating the mechanic and
ennobling his calling.

If, therefore, these schools are the representatives in our age of the
workshops with their bands of apprentices in the days of yore, then that
by which the schools are distinguished, that which they have added to
the old system, is not art but mental culture; and therefore, when asked
to address you on this occasion, I could think of no more appropriate
subject than the Nobility of Knowledge.

Identified with an institution in which mental culture is the chief aim,
I felt that I was asked to address a body of cultivated working-men with
whom, though employed in the mechanic arts, the acquisition of knowledge
was also a privilege and a pride. I felt, moreover, that a proper
appreciation of the true dignity of knowledge, in itself considered, and
apart from all economical considerations, is one of the great wants of
our age and of our country.

"Knowledge is power." "Knowledge is wealth." These trite maxims are
sufficiently esteemed in our community, and need not that they be
enforced by any one. So far as knowledge will yield immediate
distinction or gain, it is sought and fostered by multitudes. But, when
the aim is low, the attainment is low, and too many of our students are
satisfied with superficiality, if it only glitters, and with
charlatanry, if it only brings gold.

Let me not be understood to depreciate the material advantages of
learning. I rejoice that in this world knowledge frequently yields
wealth and fame, and I should have little hope for human progress were
the prizes of scholarship less than they are. Power and wealth are noble
aims, and when rightly used may be the means of conferring unmeasured
blessings on mankind; but I desire at this time to impress upon you, my
friends, the fact that knowledge has nobler fruits than these, and that
the worth of your knowledge is to be measured not by the credits it will
add to your account in the ledger, or the position it may give you among
men, but by the extent to which it educates your higher nature, and
elevates you in the scale of manhood.

I address young men who are just entering on life, who are at an age
when the mystery of our being usually presses most closely upon the
soul, and whose aspirations for higher culture and clearer vision have
not been deadened by the sordid damps of the world. Trust no croakers
who tell you that your youthful visions are illusions, which a little
contact with the real business of the world will dispel.

It is only too true that these visions will become fainter and fainter,
if you allow the cares of the world to engross your thoughts; but,
unless your higher nature becomes wholly deadened, you will look back to
the time when the visions were brightest, as the golden period of your
life, and let me assure you that, if you only are true to the
aspirations of your youth, the visions will become clearer and clearer
to the last, and, as we firmly believe, will prove to be the dawn of the
perfect day.

My friends, if you have seen these visions, "the nobility of knowledge"
has been a reality of your experience. You know that there is a life
lived in communion with the thoughts of great men or with the thoughts
of God as we can read them in Nature and Revelation, which is purer and
nobler than a life of money-making or political intrigue, and I would
that I could so bring you to appreciate not only the nobility, but also
the happiness, of such a life as to induce you to try to live it.

Do you tell me that it is only granted to a few men to become scholars,
and that you have been educated for some industrial pursuit? Remember,
as I said before, that it is your special privilege to have been
educated, to have added knowledge to your handicraft, and that this very
knowledge, if kept alive so far as you are able, will ennoble your life.
Knowledge, like the fairy's wand, ennobles whatever it touches. The
humblest occupations are adorned by it, and without it the most exalted
positions appear to true men mean and low.

Nor is it the extent of the knowledge alone which ennobles, but much
more the spirit and aim with which it is cultivated, and that spirit and
aim you may carry into any occupation, however engrossing, and into any
condition of life, however obscure.

And let me add that what I have said is true not only of the individual,
but also, and to an even greater degree, of the nation. Our people, for
the most part, look upon universities and other higher institutions of
learning as merely schools for recruiting the learned professions, and
estimate their efficiency solely by the amount of teaching work which
they perform. But, however important the teaching function of the
university may be, I need not tell you that this is not its only or
chief value to a community. The university should be the center of
scientific investigation and literary culture, the nursery of lofty
aspirations and noble thoughts, and thus should become the soul of the
higher life of the nation. For this and this chiefly it should be
sustained and honored, and no cost and no sacrifice can be too great
which are required to maintain its efficiency; and its success should be
measured by the amount of knowledge it produces rather than by the
amount of instruction it imparts.

Harvard College, by cherishing and honoring the great naturalist she
has recently lost, has done more for Massachusetts than by educating
hosts of commonplace professional men. The simple title of teacher,
which in his last will Louis Agassiz wrote after his name, was a nobler
distinction than any earthly authority could confer; but remember he was
a teacher not of boys, but of men, and his influence depended not on the
instruction in natural history which he gave in his lecture-room, but on
his great discoveries, his far-reaching generalization, and his noble
thoughts. Although that man died poor, as the world counts poverty, yet
the bequest which he left to this people can not be estimated in coin.

It is a sorry confession to make, but it is nevertheless the truth,
that, if we compare our American universities, in point of literary or
scientific productiveness, with those of the Old World, they will appear
lamentably deficient. Let me add, however, that this deficiency arises
not from any want of proper aims in our scholars, but simply from the
circumstance that our people do not sufficiently appreciate the value of
the higher forms of literary and scientific work to bear the burden
which the production necessary entails. Scholars must live, as well as
other men, and in a style which is in harmony with their surroundings
and cultivated tastes, and their best efforts can not be devoted to the
extension of knowledge unless they are relieved from anxiety in regard
to their daily bread.

In our colleges the professors are paid for teaching and for teaching
only, while in a foreign university the teaching is wholly secondary,
and the professor is expected to announce in his lectures the results of
his own study, and not the thoughts of other men. Until the whole status
of the professors in our chief universities can be changed, very little
original thought or investigation can be expected, and these
institutions can not become what they should be, the soul of the higher
life of the nation.

It is in your power, however, to bring about this change, but the reform
can be effected in only one way. You must give to your universities the
means of supporting fully and generously those men of genius who have
shown themselves capable of extending the boundaries of human knowledge,
and demand of them, only, that they devote their lives to study and
research, and let me assure you that no money can be spent which will
yield a larger or more valuable return.

If you do not look beyond your material interests, the higher life of
the nation, which you will thus serve to cherish and foster, will guard
your honor and protect your home; and, on the other hand, what can you
expect in a nation whose highest ideal is the dollar or what the dollar
will buy, but venality, corruption, and ultimate ruin?

But, rising at once to the noblest considerations, and regarding only
the welfare of your country and the education of your race, what higher
service can you render than by sustaining and cherishing the grandest
thought, the purest ideals, and the loftiest aspirations which humanity
has reached, and making your universities the altars where the holy fire
shall be kept ever burning bright and warm?

Do you think me an enthusiast? Look back through history, and see for
yourselves what has made the nations great and glorious. Why is it that,
after twenty centuries, the memory of ancient Greece is still enshrined
among the most cherished traditions of our race? Is it not because Homer
sang, Phidias wrought, and Plato, Aristotle, Demosthenes, Thucydides,
with a host of others, thought and wrote? Or, if for you the military
exploits of that classic age have the greater charm, do not forget that
were it not for Grecian literature, Thermopylæ, Marathon, and Salamis
would have been long since forgotten, and that the bravery,
self-devotion, and patriotism which these names embalm were the direct
fruits of that higher life which those great thinkers illustrated and
sustained.

And, coming down to modern times, what are the shrines in our mother
country which we chiefly venerate, and to which the transatlantic
pilgrim oftenest directs his steps? Is it her battlefields, her castles
and baronial halls, or such spots as Stratford-on-Avon, Abbotsford, and
Rydal Mount? Why, then, will we not learn the lesson which history so
plainly teaches, and strive for those achievements in knowledge and
mental culture which will be remembered with gratitude when all local
distinctions and political differences shall have passed away and been
forgotten?

While I was considering the line of discourse which I should follow on
this occasion, an incident occurred suggesting an historical parallel,
which will illustrate, better than any reflections of mine, the truth I
would enforce. The ship Faraday arrived on our coast after laying over
the bed of the Atlantic another of those electric nerves through which
pulsate the thoughts of two continents, and as I read the description of
that noble ship, fitted out with all the appliances which modern science
had created to insure the successful accomplishment of the enterprise, I
remembered that not a century had elapsed since the first obscure
phenomena were observed, whose conscientious study, pursued with the
unselfish spirit of the scientific investigator, had led to these
momentous results, and my imagination carried me back to an autumn day
of the year 1786, in the old city of Bologna, in Italy, and I seemed to
assist at the memorable experiment which has associated the name of
Aloysius Galvani with that mode of electrical energy which flashes
through the wire cords that now unite the four quarters of the globe.

Galvani is Professor of Anatomy in the University of Bologna, and there
is hanging from the iron balcony of his house a small animal
preparation, which is not an unfamiliar sight in Southern Europe, where
it is regarded as a delicacy of the table. It is the hind-legs of a
frog, from which the skin had been removed, and the great nerve of the
back exposed. Six years before, his attention had been called to the
fact that the muscles of the frog were convulsed by the indirect action
of an electrical machine, under conditions which he had found very
difficult to interpret. He had connected the phenomenon with a theory of
his own: that electricity--that is, common friction electricity, the
only mode of electrical action then known--was the medium of all nervous
action; and this had led him into a protracted investigation of the
subject, during which he had varied the original experiment in a
thousand ways, and he had now suspended the frog's legs to the iron
balcony, in order to discover if atmospheric electricity would have any
effect on the muscles of the animal.

Galvani has spent a long day in fruitless watching, when, while holding
in his hand a brass wire, connected with the muscles of the frog, he
rubs the end, apparently listlessly, against the iron railing, when,
lo! the frog's legs are convulsed.

The patient waiting had been rewarded, for this observation was the
beginning of a line of discovery which was ere long to revolutionize the
world. But Galvani was not destined to follow far the new path he had
thus opened. The remarkable fact observed was this: The convulsions of
the frog's legs could be produced without the intervention of
electricity, or, at least, of the one kind of electricity then known,
and Galvani soon found out that the only condition necessary to produce
the result was, that the nerve of the frog should be connected with the
muscle of the leg by some good electrical conductor.

But, although Galvani followed up this observation with the greatest
zeal, and showed remarkable sagacity throughout his whole investigation,
yet he was too strongly wedded to his own theory to interpret correctly
the facts he observed. He supposed, to the end of his life, that the
whole effect was caused by animal electricity flowing through the
conductor from the nerve to the muscle, and his experiments were chiefly
interesting to himself and to his contemporaries from the light they
were supposed to throw on the mysterious principle of life. We now know
that animal electricity played only a small part in the phenomena he
observed, and that the chief effects were due to a cause of which he
was wholly ignorant.

Galvani published his observations in 1791, in a monograph entitled "The
Action of Electricity in Muscular Motion." This publication excited the
most marked attention, and, within a year, all Europe was experimenting
on frogs' legs. The phenomena were everywhere reproduced, but Galvani's
explanation of the phenomena was by no means so universally accepted.
His theory was controverted in many quarters, and by no one more
successfully than by Alexander Volta, Professor of Physics in the
neighboring University of Pavia.

Volta, while admitting, with Galvani, that the muscular contractions
were caused by electricity, explained the origin of the electricity in a
wholly different way. According to Volta, the electricity originated not
in the animal, but in the contact of the dissimilar metals or other
materials used in the experiment. This difference of opinion led to one
of the most remarkable controversies in the history of science, and for
six years, until his death in 1798, Galvani was occupied in defending
his theory of animal electricity against the assaults of his
distinguished countryman.

This discussion created the liveliest interest throughout Europe. Every
scholar of science took sides with one or the other of these eminent
Italian philosophers, and the scientific world became divided into the
school of Galvani and the school of Volta. Yet, so far at least as the
fundamental experiment was concerned, both were wrong. The electricity
came neither from the body of the frog nor from the contact of
dissimilar kinds of matter, but was the result of chemical action, which
both had equally overlooked.

But, nevertheless, the controversy led to the most important results:
for Volta, while endeavoring to sustain his false theory by experimental
proofs, was led to the discovery of the Voltaic pile, or, as we now call
it, the Voltaic battery, an instrument whose influence on civilization
can be compared only with the printing-press and the steam-engine. Yet,
although the whole action of the battery was in direct contradiction to
his pet theory, still, to the last, Volta persistently defended the
erroneous doctrine he had espoused in his controversy with Galvani
thirty years before, and he died in 1827, without realizing how great a
boon he had been instrumental in conferring on mankind; so true it is
that Providence works out his bright designs even through the blindness
and mistakes of man.

But there is another lesson to be learned from this history, which can
not be too often rehearsed in this self-sufficient age, which boasts so
proudly of its practical wisdom. There were, doubtless, many practical
men in that city of Bologna to smile at their sage professor, who had
spent ten long years in studying, to little apparent purpose, the
twitchings of frogs' hind-legs, and there was many a jest among the
courtiers of Europe at the expense of the learned philosophers who
"wasted" so much time in discussing the cause of such trivial phenomena.
But how is it now?

Less than a century has passed since Galvani's death, and in a small hut
on the shores of Valentia Bay may be seen one of the most skillful of a
new class of practical men, representing a profession which owes its
origin to Galvani and Volta. The _electrician_ is watching a spot of
light on the scale of an instrument which is called a _galvanometer_.
Since the fathers fell asleep, the field of knowledge which they first
entered has spread out wider and wider before the untiring explorers who
have succeeded them. Oersted and Seebeck, Arago and Ampère, Faraday and
our own Henry, have made wonderful discoveries in that field; and other
great men, like Steinheil, Wheatstone, Morse, and Thomson, have invented
ingenious instruments and appliances, by which these discoveries might
be made to yield great practical results.

The spot of light, which the electrician is watching, is reflected from
one of the latest of these inventions, the reflecting galvanometer of
Thomson. He and his assistants had been watching by turns the same spot
for several days, since the Great Eastern had steamed from the bay,
paying out a cable of insulated wire. These electricians had no anxiety
as to the result, for daily signals had been exchanged between the ship
and the shore, as hundreds after hundreds of miles of this electrical
conductor had been laid on the bed of the broad ocean. The coast of
Newfoundland had already been reached, and they were only waiting for
the landing of the cable at the now far-distant end.

At length the light quivers, and the spot begins to move. It answers to
concerted signals. And soon the operator spells out the joyful message.
The ocean has been spanned with an electric nerve, and the New World
responds to the greetings of the Old.

Here is something practical, which all can appreciate, and all are ready
to honor. We honor the courage which conceived, the skill which
executed, and, above all, the success which crowned the undertaking. But
do we not forget that professor of Bologna, with his frogs' legs, who
sowed the seed from which all this has sprung? He labored without hope
of temporal reward, stimulated by the pure love of truth, and the grain
which he planted has brought forth this abundant harvest. Do we not
forget, also, that succession of equally noble men, Volta, and Oersted,
and Faraday, with many other not less devoted investigators of
electrical science, without whose unselfish labors the great result
never could have been achieved? Such men, of course, need no recognition
at our hands, and I ask the question not for their sakes, but for ours.
The intellectual elevation of the lives they led was their
all-sufficient reward.

It is, however, of the utmost importance for us, citizens of a country
with almost unlimited resources, that we should recognize what are the
real springs of true national greatness and enduring influence. In this
age of material interests, the hand is too ready to say to the head, "I
have no need of thee"; and, amid the ephemeral applause which follows
the realization of some triumph over matter, we are apt to be deceived,
and not observe whence the power came. We associate the great invention
with some man of affairs man who overcame the last material obstacle,
and who, although worthy of all praise, probably added very little to
the total wealth of knowledge of which the invention was an immediate
consequence; and, not seeing the antecedents, we are apt to underrate
the part which the student or scientific investigator may have
contributed to the result.

It is idle, for example, to speak of the electric telegraph as invented
by any single man. It was a growth of time, and many of the men who
contributed to win this great victory of mind over space "builded far
better than they knew." As I view the subject, that invention is as
much a gift of Providence as if the details had been supernaturally
revealed. But, whatever may be our speculative views, it is of the
utmost importance to the welfare of our community that we should realize
the fact that purely theoretical scientific study, pursued for truth's
sake, is the essential prerequisite for such inventions. Knowledge is
the condition of invention. The old Latin word _invenio_ signifies _to
meet with_, as well as to _find_, and these great gifts of God are _met
with_ along the pathway of civilization; but the throng of the world
passes them unnoticed, for only those can recognize the treasure whose
minds have been stored with the knowledge which the scholar has
discovered and made known.

If, then, as no one will deny, science and scholarship are the powers by
which improvements in the useful arts are made, I might appeal to your
self-interest to support and cherish them. But I should despise myself
for appealing to such a motive, and you for requiring it. The supreme
importance of science and scholarship to a nation does not depend in the
least on the circumstance that important practical results may follow.
When, as in the case of Galvani's frogs, they come in the order of
Providence, let us thank God for them as a gift which we had no right
either to expect or demand. Science, if studied successfully, must be
studied for the pure love of truth; and, if we serve her solely for
mercenary ends, her truths, the only gold she offers, will turn to dross
in our hands, and we shall degrade ourselves in proportion as we
dishonor her.

Galvani, and Volta, and Oersted, who discovered the truths of which the
electric telegraph is a simple application, sure to be made as soon as
the time was ripe, are not the less to be honored because they died
before the fullness of that time had come. We honor them for the truths
they discovered, and the lustre of their consecrated lives could be
neither enhanced nor impaired by subsequent events; and it is because I
am persuaded that such lives are the salt of the world, the saviours of
society, that I would lead you to cherish and sustain them; and, that I
may enforce this conclusion, allow me to ask your attention to another
historical incident, which presents a striking parallelism to the last.

I must take you back to a period which we, of a nation born but
yesterday, regard as distant, but which was one of the most noted epochs
of modern history--the age of Luther and the Reformation. I must ask you
to accompany me to the small town of Allenstein, near Frauenberg, in
Eastern Prussia, where, on May 23, 1543, there lay dying one of the
great benefactors of mankind.

This man, old at seventy years, "bent and furrowed with labor, but in
whose eye the fire of genius was still glowing," was then known as one
of the most learned men of his time. Doctor of medicine as well as of
theology, Canon of Frauenberg, Honorary Professor of Bologna and Rome,
while devoting his leisure to study, he had passed a life of active
benevolence in administering to the bodily as well as the spiritual
wants of the ignorant people among whom his lot had been cast. He was
also a great mechanical genius, and, by various labor-saving machines,
of his own invention, he had contributed greatly to the welfare of the
surrounding country.

But the superstitious peasants, although they had hitherto reverenced
the great man as their best friend and benefactor, had been recently
incited by his enemies and rivals in the church to curse him as a
heretic and a wizard. A few days back he had been the unwilling witness
of one of those out-of-door spectacles, so common at that time, in which
his scientific opinions had been travestied, his charities ridiculed,
and his devoted life made the object of slander and reproach. This
ingratitude of his flock had broken his heart, and he could not recover
from the blow.

The occasion of this outburst of fanaticism was the approaching
publication of a work in which he had dared to question the received
opinions of theologians and schoolmen, in regard to cosmogony. He had,
forsooth, denied that the visible firmament was a solid azure-colored
shell, to which the sun and planets were fastened, and through whose
opened doors the rain descended. He had proved that the sun was the
center of the system, around which the earth and planets revolved, and,
with his clear scientific vision, he had been able to gain glimpses, at
least, of the grand conceptions of modern astronomy: For this man was
Nicolas Copernicus, and the expected book was his great work--"De Orbium
Coelestium Revolutionibus"--destined to form the broad basis of
astronomical science.

The work was printing at Nuremberg, and the last proofs had been
returned; but reports had come that a similar outburst of fanaticism was
raging at that place, that a mob had burned the manuscript on the public
square, and had threatened to break the press should the printing
proceed. But, thanks to God! the old man was not to die before the hour
of triumph came. While still conscious, a horse, covered with foam,
gallops to the door of his humble dwelling, and an armed messenger
enters the chamber, who, breathless with haste, places in the hands of
the dying man a volume still wet from the press. He has only strength to
return a smile of recognition, and murmur the last words:

  "Nunc dimittis servum tuum, Domine."

Grand close of a noble life! The seed has been sown--what could we
desire more?

Again the centuries roll on--not one, but three--while the seed grows to
a great tree, which overshadows the nations. Great minds have never been
wanting to cherish and prime it, like Tycho Brahe and Kepler, Galileo
and Newton, Laplace and Lagrange; and although at times some, while
lingering in the deep shade of the foliage, may have lost sight of the
summit, the noble tree has ever pointed upward to direct aspiration and
encourage hope.

On the evening of the 24th of September, 1846, in the Observatory of
Berlin, a trained astronomical observer was carefully measuring the
position of a faint star in the constellation Capricorn. Only the day
before, he had received from Le Verrier a letter announcing the result
of that remarkable investigation which has made the name of this
distinguished French astronomer so justly celebrated. By the studies of
the great men who succeeded Copernicus, his system had become so
perfected as to enable the astronomer to predict, with unerring
certainty, the paths of the planets through the heavens. But there was
one failing case. The planet Uranus, then supposed to be the outer
planet of the solar system, wandered from the path which theory assigned
to it; and although the deviations were but small, yet any discrepancy
between theory and observation in so accurate a science as astronomy
could not be overlooked.

Long before this, the hypothesis had been advanced that the deviations
were caused by the attractive force of an unseen and still more distant
planet; but, as no such planet had been discovered, the hypothesis had
remained until now wholly barren. The hypothesis, however, was
reasonable, and furnished the only conceivable explanation of the facts;
and, moreover, if true, the received system of astronomy ought to be
able to assign the position and magnitude of the disturbing body, the
magnitude and direction of the displacements being given.

This possibility was generally appreciated by astronomers, and the very
great length and difficulty of the mathematical calculation which the
investigation involved was probably the reason that no one had hitherto
undertaken it. Le Verrier, however, had both the courage and the
youthful strength required for the work. And now the great work had been
done; and, on the 18th of September, Le Verrier had sent to the
Observatory of Berlin his communication announcing the final result,
namely, that the planet would be found about 5° to the east of the star
Delta of Capricorn.

The letter containing this announcement was received by Galle, at
Berlin, on the 23d, and it was Galle whom we left measuring the position
of that faint star on the evening of the 24th. It so happened that a
chart of that portion of the heavens had recently been prepared by the
Berlin Observatory, and was on the eve of publication; and, on the very
evening he received the letter, Galle had found, near the position
assigned by Le Verrier, a faint star, which was not marked on this
chart. The object differed in appearance from the surrounding stars, but
still it was perfectly possible that it might be a fixed star which had
escaped previous observation.

But, if a fixed star, its position in the constellation would not vary,
while, if a planet, a single night would show a perceptible change of
place. Hence, you may conceive of the interest with which Galle was
measuring anew its position on the evening of the 24th.

The star had moved, and in the direction which theory indicated; and for
once, at least, the world rang with applause at a brilliant scientific
conquest from which there was not one cent of money to be made. Yet, was
that conquest any less important to the world? What had it secured? It
had confirmed the theory of astronomy which Copernicus and his
successors had built up, and it had clinched the last nail in the proof
that those grand conceptions of modern astronomy, now household
thoughts, are realities, and not dreams. Certainly no military conquest
can compare with this.

Do not smile at the enthusiasm which rates so high a purely intellectual
achievement? Go out with me under the heavens, in some starlight night,
and, looking up into the depths of space, recall the truths you have
learned in regard to that immensity, and allow the imagination free
scope as it stretches out into the infinitudes of time, space, and
power, carrying the mind on, bound by bound, through the limitless
expanse, until even the imagination refuses to follow, and fairly quails
before the mighty form of the Infinite, which rises to confront it!
Remember now that your forefathers, of only a few centuries back, saw
there nothing but a solid dome hemming in the earth and skies, and that
you are able to look upon this grand spectacle only because great minds
have lived who have opened your intellectual eyes; and then answer me,
is not this result worth all the labor, all the sacrifice, all the
treasure it has cost?

Every educated man, who has not sold his birthright for a mess of
pottage, lives a grander and nobler life, because the great astronomers
have thought and taught, and this elevation of human life is the
greatest achievement of which man can boast. Before it all material
conquests appear of little worth, and the lustre of all military or
civil glory grows dim. Cherish this intellectual life; foster it;
sustain it; do what you can by your own spirit and influence, and, if
you are blessed with riches, give of your abundance to support and
encourage those who, by genius, talent, and devotion, will widen the
intellectual kingdom. Be assured you will thus help to confer an
inestimable boon on your race and on your country; and the influence for
good will not be felt by the intellectual life of the nation only. That
corruption which is now festering at the heart of our body politic, and
threatening its destruction, can in no way be fought and conquered so
effectually as by keeping constantly before the nation noble and high
ideals; for, where the higher life is cherished and honored, the
mercenary and sensual motives of action, which both invite and shield
corruption, lose much of their force and power.

But you may tell me that there is a life higher than the intellectual
life, and that I have ascribed to science and scholarship influences
which come only from a source which I have forgotten, or left out of
view. My friends, all truth is one and inseparable, and I have therefore
made no distinction in this address between the truths of science and
truths of religion. The grand old word knowledge, as I have used it,
includes both, and, in just the proportion that you reverence religion,
you must reverence also true science. All truth is God's truth, and, in
praying for the coming of his kingdom, you certainly do not expect that
Nature will be divorced from Grace. If the truths of religion required a
special revelation, it must be expected that they would transcend human
intelligence. These very conditions imply conflict, but the conflict
comes not from the knowledge, but from the ignorance and conceit of men;
and the only proper attitude for the devout scholar is "to labor and to
wait." And what more wonderful confirmation could we have of the
essential unity of the two phases of truth than is to be found in the
fact that the characteristic of science, which I have been endeavoring
to illustrate in this address, is the great prominent feature of
Christianity? Christianity was revealed in a life, and ever abides a
life in the soul of man, to purify, ennoble, and redeem humanity.

  "And so the Word had breath, and wrought,
      With human hands, the creed of creeds,
      In loveliness of perfect deeds,
  More strong than all poetic thought--

  "Which he may read that binds the sheaf,
      Or builds the house, or digs the grave,
      And those wild eyes that watch the wave,
  In roarings round the coral reef."




III.

THE ELEMENTARY TEACHING OF PHYSICAL SCIENCE.

    _An Address to the Schoolmasters of Boston, delivered
    February 4, 1878._


I felt a great reluctance at accepting the invitation of your excellent
superintendent to address you on this occasion; for, although I could
claim an unusually long experience in presenting the elements of
physical science to college students, I was fully conscious that I knew
little of the conditions under which such subjects must be studied, if
at all, in the elementary schools, and was therefore in danger of
appearing in a capacity which I should most sedulously shun, that of a
babbler about impracticable theories of education. It is very easy to
criticize another man's labor, and such criticisms, however plausible,
do the grossest injustice when, as is often the case, they leave out of
view the necessary conditions and limitations under which the work must
be done. While, however, I felt most keenly my incapacity to deal with
many of the practical problems which you have to solve, yet, on
consideration, I concluded that it was my duty under the circumstances
to state as clearly and forcibly as I could the very definite opinions
which I had formed on the subject you are discussing, knowing that you
will only give such weight to these opinions as your mature judgment can
allow. In stating the results of my experience, I can not avoid a
certain personal element, which would be wholly inexcusable were it not
that the facts, as I think you will admit, form the basis of my
argument.

I am a Boston boy, born in this immediate neighborhood, and fitted for
college at the "Latin School." It so happened that, while I was very
unsuccessfully endeavoring to commit to memory, in the old school-house
on School Street, Andrews and Stoddard's Latin grammar, not one word of
which I could understand, the "Lowell Institute" lectures were opened at
the "Odeon" on Congress Street. At those lectures I got my first taste
of real knowledge, and that taste awakened an appetite which has never
yet been satisfied. As a boy, I eagerly sought the small amount of
popular science which the English literature of that day afforded; and I
can now distinctly recall almost every page of Mrs. Marcet's
"Conversations on Chemistry," which was the first book on my science
that I ever read. More to the point than this, a boy's pertinacity,
favored by a kind father's indulgence, found the means of repeating, in
a small way, most of the experiments first seen at the Lowell Institute
lecture; and thus it came to pass that, before I entered college, I had
acquired a real, available knowledge of the facts of chemistry;
although, with much labor and intense weariness, I had gained only a
formal knowledge of those subjects which were then regarded as the only
essential preparation for the college course. In college, my attention
was almost exclusively devoted to other studies--for, in my day at
Cambridge, chemistry was one of the lost arts. But when, the year after
I graduated, I was most unexpectedly called upon to give my first course
of lectures, the only laboratory in which I had worked was the shed of
my father's house on Winthrop Place, and the only apparatus at my
command was what this boy's laboratory contained. With these simple
tools, or, as I should rather say, because they were so simple, I gained
that measure of success which determined my subsequent career.

I feel that I owe you a constant apology for these personal details, and
I should not be guilty of them did I not believe that they establish two
points more conclusively than I could prove them in any other way.
First, that it is perfectly possible for a child before fifteen years
of age to acquire a real and living knowledge of the fundamental facts
of nature on which physical science is based. Secondly, that this
knowledge can be effectually gained by the use of the simplest tools.
Let me add that this is not a question of natural endowments or special
aptitudes, for every one who has studied from the love of knowledge has
had the same experience; and I do not believe that, if my first taste of
real knowledge had been of history, nay, I will even say, of philology,
instead of chemistry, the circumstance would have materially influenced
my success in life, however different the direction into which it might
have turned my study. My early tastes were utterly at variance with all
my surroundings and all my inheritances, and were simply determined by
the accident which first satisfied that natural thirst for knowledge
which every child experiences to a greater or less degree--a desire most
rudely repressed in our usual methods of teaching.

My bitter experience as a pupil in the Boston Latin School and my
subsequent more fortunate experience of thirty years as a teacher in
Harvard College have impressed me most profoundly with the conviction
that the only way to arouse and sustain a love for knowledge in children
is to cultivate their perceptive faculties. To present the rudiments of
knowledge to immature minds in an abstract form, whether the subject be
grammar or physical science, is, in my judgment, not only culpable
folly, but also downright wrong. And, if, to those who have been
accustomed to the long established routine of our public school, my
opinions may appear revolutionary and extreme, I am, nevertheless, sure
that they would receive the universal assent of the men whom all would
recognize as the foremost scientific teachers of the world. I can well
remember that when, many years ago, the late Professor Agassiz declared
in my hearing that he would have no text-books used in his museum, I
thought his plan of pure object-teaching chimerical in the extreme, and
yet experience has not only convinced me of the wisdom of his judgment
in regard to the teaching of natural history, but brought me to a
similar conclusion in regard to the elementary teaching both of natural
philosophy and of chemistry.

Allow me then to express my firm persuasion that it is not only useless
but injurious to the education of young minds to present to them at the
outset any department of physical science as a body of definitions,
principles, laws, or theories; and that in elementary schools only such
facts should be taught as can be verified by the experience of the
pupil, or by such simple experiments as the pupils can try for
themselves. The usual method of committing by heart the words of a
school-book, and repeating them at the dictation of a teacher, may
afford a good exercise for the memory, but it is absurd to regard such a
task as a lesson in physical science, and this kind of study can be
spent with vastly greater profit on the spelling-book.

There is one department of physical science which has been taught in
this absurd way in our schools from time immemorial. I refer, of course,
to the study of geography, and I leave for you to judge whether the
result is worth the one hundredth part of the toil and drudgery spent in
obtaining it. Let us suppose that your child is able to give you the
names of all the rivers, bays, and capes from Greenland to Patagonia,
how much more does that child know of the structure and social relations
of this globe on which its lot has been cast than it did before this
senseless feat was attempted, a feat, moreover, to which only a child's
memory would be equal? And, when you turn to your own experience, what
is the outcome of all the time and labor spent on geography? Is it not
solely just that portion of your knowledge which, in spite of the
system, was direct object-teaching--the images you insensibly acquired
from the maps and pictures in the school-books?

But there is a very different way of teaching geography, by which the
study may be made a pleasure, not a task. The teacher does not begin
with abstract definitions of rivers, and bays, and oceans, which convey
no definite meaning to a child, but with Charles River, Boston Harbor,
and the Atlantic Ocean, which are to him real things, however imperfect
his conceptions of their extent. The child is first shown, not a map of
the globe, which he can not by any possibility understand, but a map of
a very limited region around his own home. He is taught how to find the
north and south, the east and west directions. He is encouraged to make
excursions to verify the map, or to add to its details, and such
excursions may be made to have for him all the zest of voyages of
discovery; and when thus the rudiments of geographical science have been
mastered, not in technical terms, but in substance, then the teacher may
begin to expand the horizon of the pupil's knowledge, judiciously
omitting details in proportion as distance increases, until at length
the general survey embraces the globe. Of course, such teaching as this
can only be given orally with the help of proper apparatus, such as wall
maps, and globes, and photographs. It must take the interrogative form,
and the questions should be directed to bring out the child's already
acquired knowledge, and to lead him to observe facts which had hitherto
escaped his notice. What a child reads in a book, or even what you tell
him, is never one half learnt, unless his interest is aroused. But what
a child observes for himself he never forgets, and when you have thus
aroused his interest you can associate a large number of facts with one
observation, and these all crystallize in his memory around this
nucleus.

This is no mere theory, no untried method which I am advocating. So far
from it, I am describing the precise method which has been used for many
years in Germany, where the science of education is far better
understood than with us, and where economy both of time and labor in
teaching is most carefully studied. If our school committees could
attend and understand a single exercise in geography, such as are daily
given in the elementary schools of Prussia, I am sure that at least one
form of child torture would soon disappear from the primary schools of
this country. Indeed, I already see evidence of a growing public opinion
on this subject, an effect which I trace in no small measure to the
influence of the Department of Education of the Exhibition at
Philadelphia in 1876.

That which is true of geography applies with still greater force to such
subjects as physics and chemistry, since the abstract conceptions which
these sciences involve are more abstruse, and the language by which the
conceptions are expressed or defined far less plain than is the case
with the older and more descriptive branch of knowledge. Hence, as
sciences, properly so called, that is, as philosophical systems, they
have no place whatever in elementary education. But, underlying these
systems, there is a great multitude of phenomena which a child can be
led to observe and apprehend as readily as the facts of geography. Take
that subject--mechanics--which our ordinary school-books very
philosophically but most unpractically place at the beginning of what
they call "Natural" Philosophy. How many of the fundamental facts of
this difficult subject can be made familiar to a child? Select, as an
example, Newton's "First Law of Motion." Suppose you make a boy memorize
the ordinary rule, "Every body continues in a state of rest or of
uniform motion in a straight line until acted upon by some external
force," how much will he know about it? Suppose you make him do a lot of
problems involving distances, velocities, and times, will he know any
more about it? But ask him, "Can you pitch a ball as well as your
playmate?" and he answers at once, "No; John is stronger than I am." And
then, if again you ask, "Can you catch John's ball?" he will probably
reply, "Of course, not! It requires a boy as strong as John to catch his
balls." And thus, by a few well-directed questions, you would bring that
boy to learn a lesson which he would never forget, and which he would
recall every time he played base-ball; namely, that John's swift balls
could not be set in motion without an expenditure of a definite amount
of muscular effort, and could not be stopped without the exertion of an
equal amount of what, after a while, you could get him to call _force_.
From the ball you would naturally pass to the railroad train or the
steamboat, and I should not wonder if, with a little patience, you could
bring even a boy to understand that motion can not be maintained against
a resistance, in other words, that work can not be done without a
constant expenditure of muscular effort, or of some other source of
power; and it is a fond hope of mine that by the time these boys grow
into men our intelligent New England community might become so far
educated in the elementary principles of mechanics that no
self-sustained motors, nor other mechanical nostrums which claim to have
superseded the primeval curse--if that law was a curse, which compels
man to earn his bread with the sweat of his brow--will receive the
sanction of our respectable journals; and then--if they have not
previously learned the lesson by dire experience--we may hope to
persuade our people of the parallel and equally elementary principle of
political economy, that value can not be legislated into rags.

But, my friends, our subject gives no occasion for banter, and presents
aspects too serious to be treated lightly or in jests. As inhabitants of
a not over-fruitful land, and, therefore, members of a community which
must excel, if at all, solely by its enterprise and intelligence, we
have a duty to our children which we can not avoid, if we would, and for
which we shall be held responsible by our posterity. These children are
entering life surrounded not only by all the wonders and glories of
nature, but, also, by giant conditions, which, whether stationed on
their path as a blessing or a curse, will inevitably strike if their
behests are not obeyed. So far as science has been able to define these
giant forms, it is our duty, as it is our privilege, to point them out
to those we are bound to protect and guide; and in many cases it is in
our power to change the curse into a blessing, and to transform the
destructive demon into a guardian angel. After that command of language
which the necessities of civilized life imperatively require, there is
no acquisition which we can give our children that will exert so
important an influence on their material welfare as a knowledge of the
laws of nature, under which they must live and to which they must
conform; and throughout whose universal dominion the only question is
whether men shall grovel as ignorant slaves or shall rule as intelligent
servants. Yes; rule by obeying. "Ich Dien"; for only under that motto,
which, five hundred years ago, the great Black Prince bore so
victoriously through the fields of Cressy and Poitiers, can man ever
rule in Nature's kingdom.

I regard it, therefore, as the highest duty and the most enlightened
self-interest of a community like this to provide the best means for the
instruction of its children in the elements of physical science; and I
was, therefore, most anxious to do all in my power to second the
enlightened efforts of your eminent Superintendent in this direction.
You must remember, however, that the best tools are worthless in
themselves, and can secure no valuable results unless judiciously used.
Indeed, there is danger in too many tools, and I have a great horror of
that array of brass-work which is usually miscalled "philosophical"
apparatus. The greater part of this is, in my opinion, a mere hindrance
to the teacher, because it at once erects a barrier between the scholar
and the simple facts of nature, and the child inevitably associates with
the phenomenon illustrated some legerdemain, and looks on your
experiments very much as he would on the exhibition of a Houdin or a
Signor Blitz. The secret of success in teaching physical science is to
use the simplest and most familiar means to illustrate your point.

When a very young man I was favored with an introduction to Michael
Faraday, and had the privilege of attending a portion of a course of
lectures which this noble man was then in the habit of giving every
Christmas season to a juvenile auditory at the Royal Institution of
London. As a boy, I had become familiar with lectures on chemistry at
the Lowell Institute, where they did not lack the pomp of circumstance
or the display of apparatus, and I had come to associate these elements
with the conditions of success in lectures of this kind. What, then, was
my surprise to find Faraday, the acknowledged leader of the world in his
science, and who had every means of illustration at his command, using
the plainest language and the simplest tools. When, in my youthful
admiration at the result, I expressed, after one of the lectures, my
surprise at the simplicity of the means employed, the great master
replied: "That is the whole secret of interesting these young people. I
always use the simplest means, but I never leave a point not
illustrated. If I mention the force of gravitation I take up a stone and
let it drop." At this distance of time, I can not be sure that I quote
his exact language, but the lesson and the illustration I could not
forget; and to this lesson, more than to any other one thing, I owe
whatever success I have had as a teacher of physical science.

I repeat, therefore, it is not only useless but injurious in the
education of young minds to present any department of physical science
as a body of definitions, principles, laws, or theories; and that in
elementary schools such facts only should be taught as can be verified
either by the experience of the pupils or by the simplest experiments,
which the pupils can repeat by themselves; and now, after this
discussion, I add, that the teacher must depend on his own ingenuity for
his experiments, and on his intercourse with his pupils for his
instruction.

But you will tell me all this involves grave difficulties, and
conditions incompatible with our ordinary school life. I freely admit
the difficulties, but I am none the less sure that, unless science can
be taught on the principles I have endeavored to illustrate, it had
better not be taught at all. I know very well that the proper teaching
of physical science is wholly incompatible with our usual school
methods. But this only proves to me that these methods ought to be
changed, and I am persuaded that the changes required will benefit the
literary and classical as well as the scientific courses of study. For
do not the same general principles apply to the acquisition of knowledge
in all subjects? And when a child's perceptive faculties have been duly
stimulated, and his intelligence fully awakened, he will find interest
in grammar, in literature, or in history, as well as in science.

In repelling the reproach of narrowness, to which our elective system at
Cambridge undoubtedly frequently leads, how often have I urged the
self-evident proposition that to arouse a love of study in any subject,
I care not how subordinate its importance or how limited its scope, is
to take the first step toward making your man a scholar; while to fail
to gain his interest in any study is to lose the whole end of
education--and what is true of the man is still more true of the child.
Classical culture on the one hand and scientific culture on the other
are excellent things, but, if your boy can not be made to take an
interest either in classics or in science, how plain it is that such
treasures are not for him, and, in the absence of the one condition
which can give value to any study, how idle and inconsequent all
questions in regard to the relative merits of these studies appear! On
the other hand, a love of study once gained, all studies are alike good.

And as with the pupil, so with the teacher. No teaching is of any real
value that does not come directly from the intelligence, and heart of
the teacher, and thus appeals to the intelligence and heart of the
pupil. It, of course, implies more acquisition, and it requires far more
energy to teach from one's own knowledge than to teach from a book, but
then, just in proportion to the difficulties overcome, does the teacher
raise his profession and ennoble himself. There is no nobler service
than the life of a true teacher; but the mere task-master has no right
to the teacher's name, and can never attain the teacher's reward.




IV.

THE RADIOMETER: A FRESH EVIDENCE OF A MOLECULAR UNIVERSE.

    _A Lecture delivered in the Sanders Theatre of Harvard
    University, March 6, 1878._


No one who is not familiar with the history of physical science can
appreciate how very modern are those grand conceptions which add so much
to the loftiness of scientific studies; and, of the many who, on one of
our starlit nights, look up into the depths of space, and are awed by
the thoughts of that immensity which come crowding upon the mind, there
are few, I imagine, who realize the fact that almost all the knowledge
which gives such great sublimity to that sight is the result of
comparatively recent scientific investigation; and that the most
elementary student can now gain conceptions of the immensity of the
universe of which the fathers of astronomy never dreamed. And how very
grand are the familiar astronomical facts which the sight of the starry
heavens suggests!

Those brilliant points are all suns like the one which forms the center
of our system, and around which our earth revolves; yet so inconceivably
remote, that, although moving through space with an incredible velocity,
they have not materially changed their relative position since recorded
observations began. Compared with their distance, the distance of our
own sun--92,000,000 miles--seems as nothing; yet how inconceivable even
that distance is when we endeavor to mete it out with our terrestrial
standards! For if, when Copernicus--the great father of modern
astronomy--died, in 1543, just at the close of the Protestant
Reformation, a messenger had started for the sun, and traveled ever
since with the velocity of a railroad train--thirty miles an hour--he
would not yet have reached his destination!

Evidently, then, no standards, which, like our ordinary measures, bear a
simple or at least a conceivable relation to the dimensions of our own
bodies, can help us to stretch a line in such a universe. We must seek
for some magnitude which is commensurate with these immensities of
space; and, in the wonderfully rapid motion of light, astronomy
furnishes us with a suitable standard. By the eclipses of Jupiter's
satellites the astronomers have determined that this mysterious
effluence reaches us from the sun in eight minutes and a half, and
therefore must travel through space with the incredible velocity--shall
I dare to name it?--of 186,000 miles in a second of time! Yet,
inconceivably rapid as this motion is, capable of girdling the earth
nearly eight times in a single second, the very nearest of the fixed
stars, [alpha] Centauri, is so remote that the light by which it will
be seen in the southern heavens to-night, near that magnificent
constellation, the Southern Cross, must have started on its journey
three years and a half ago. But this light comes from merely the
threshold of the stellar universe; and the telescope reveals to us stars
so distant that, had they been blotted out of existence when history
began, the tidings of the event could not yet have reached the earth!

Compare now with these grand conceptions the popular belief of only a
few centuries back. Where we look into the infinite depths, our Puritan
forefathers saw only a solid dome hemming in the earth and skies, and
through whose opened doors the rain descended. They regarded the sun and
moon merely as great luminaries set in this firmament to rule the day
and night, and to their understandings the stars served no better
purpose than the spangles which glitter on the azure ceiling of many a
modern church. The great work of Copernicus, "De Orbium Coelestium
Revolutionibus," which was destined, ultimately, to overthrow the crude
cosmography which Christianity had inherited from Judaism, was not
published until just at the close of the author's life in 1543, the date
before mentioned. The telescope, which was required to fully convince
the world of its previous error, was not invented until more than half a
century later, and it was not until 1835 that Struve detected the
parallax of [alpha] Lyræ. The measurement of this parallax, together
with Bessel's determination of the parallax of 61 Cygni, and Henderson's
that of [alpha] Centauri, at about the same time, gave us our first
accurate knowledge of the distances of the fixed stars.

To the thought I have endeavored to express, I must add another, before
I can draw the lesson which I wish to teach. Great scientific truths
become popularized very slowly, and, after they have been thoroughly
worked out by the investigators, it is often many years before they
become a part of the current knowledge of mankind. It was fully a
century after Copernicus died, with his great volume--still wet from the
press of Nuremberg--in his hands, before the Copernican theory was
generally accepted even by the learned; and the intolerant spirit with
which this work was received and the persecution which Galileo
encountered more than half a century later were due solely to the
circumstance that the new theory tended to subvert the popular faith in
the cosmography of the Church. In modern times, with the many popular
expositors of science, the diffusion of new truth is more rapid; but
even now there is always a long interval after any great discovery in
abstract science before the new conception is translated into the
language of common life, so that it can be apprehended by the mass even
of educated men.

I have thus dwelt on what must be familiar facts in the past history of
astronomy, because they illustrate and will help you to realize the
present condition of a much younger branch of physical science; for, in
the transition period I have described, there exists now a conception
which opens a vision into the microcosmos beneath us as extensive and as
grand as that which the Copernican theory revealed into the macrocosmos
above us.

The conception to which I refer will be at once suggested to every
scientific scholar by the word _molecule_. This word is a Latin
diminutive, which means, primarily, a small mass of matter; and,
although heretofore often applied in mechanics to the indefinitely small
particles of a body between which the attractive or repulsive forces
might be supposed to act, it has only recently acquired the exact
significance with which we now use it.

In attempting to discover the original usage of the word molecule, I
was surprised to find that it was apparently first introduced into
science by the great French naturalist, Buffon, who employed the term in
a very peculiar sense. Buffon does not seem to have been troubled with
the problem which so engrosses our modern naturalists--how the vegetable
and animal kingdoms were developed into their present condition--but he
was greatly exercised by an equally difficult problem, which seems to
have been lost sight of in the present controversy, and which is just as
obscure to-day as it was in Buffon's time, at the close of the last
century, and that is, Why species are so persistent in Nature; why the
acorn always grows into the oak, and why every creature always produces
of its kind. And, if you will reflect upon it, I am sure you will
conclude that this last is by far the more fundamental problem of the
two, and one which necessarily includes the first. That, of two eggs, in
which no anatomist can discover any structural difference, the one
should, in a few short years, _develop_ an intelligence like Newton's,
while the other soon ends in a Guinea-pig, is certainly a greater
mystery than that, in the course of unnumbered ages, monkeys, by
insensible gradations, should _grow_ into men.

In order to explain the remarkable constancy of species, Buffon advanced
a theory which, when freed from a good deal that was fanciful, may be
expressed thus: The attributes of every species, whether of plants or
of animals, reside in their ultimate particles, or, to use a more
philosophical but less familiar word, _inhere_ in these particles, which
Buffon names _organic molecules_. According to Buffon, the oak owes all
the peculiarities of its organization to the special oak molecules of
which it consists; and so all the differences in the vegetable or animal
kingdom, from the lowest to the highest species, depend on fundamental
peculiarities with which their respective molecules were primarily
endowed. There must, of course, be as many kinds of molecules as there
are different species of living beings; but, while the molecules of the
same species were supposed to be exactly alike, and to have a strong
affinity or attraction for each other, those of different species were
assumed to be inherently distinct and to have no such affinities. Buffon
further assumed that these molecules of organic nature were diffused
more or less widely through the atmosphere and through the soil, and
that the acorn grew to the oak simply because, consisting itself of oak
molecules, it could draw only oak molecules from the surrounding media.

With our present knowledge of the chemical constitution of organic
beings, we can find a great deal that is both fantastic and absurd in
this theory of Buffon; but it must be remembered that the science of
chemistry is almost wholly a growth of the present century, while
Buffon died in 1788; and, if we look at the theory solely from the
standpoint of his knowledge, we shall find in it much that was worthy of
this great man. Indeed, in our time, the essential features of the
theory of Buffon have been transferred from natural history to chemistry
almost unchanged.

According to our modern chemistry, the qualities of every substance
reside or inhere in its molecules. Take this lump of sugar. It has
certain qualities with which every one is familiar. Are those qualities
attributes of the lump or of its parts? Certainly of its parts; for, if
we break up the lump, the smallest particles will still taste sweet and
show all the characteristics of sugar. Could we, then, carry on this
subdivision indefinitely, provided only we had senses or tests delicate
enough to recognize the qualities of sugar in the resulting particles?
To this question, modern chemistry answers decidedly, No! You would
before long reach the smallest mass that can have the qualities of
sugar. You would have no difficulty in breaking up these masses, but you
would then obtain, not smaller particles of sugar, but particles of
those utterly different substances which we call carbon, oxygen, and
hydrogen--in a word, particles of the elementary substances of which
sugar consists. These ultimate particles of sugar we call the molecules
of sugar, and thus we come to the present chemical definition of a
molecule, "_The smallest particles of a substance in which its qualities
inhere_," which, as you see, is a reproduction of Buffon's idea,
although applied to matter and not to organism.

A lump of sugar, then, has its peculiar qualities because it is an
aggregate of molecules which have those qualities, and a lump of salt
differs from a lump of sugar simply because the molecules of salt differ
from those of sugar, and so with every other substance. There are as
many kinds of molecules in Nature as there are different substances, but
all the molecules of the same substance are absolutely alike in every
respect.

Thus far, as you see, we are merely reviving in a different association
the old ideas of Buffon. But just at this point comes in a new
conception, which gives far greater grandeur to our modern theory: for
we conceive that those smallest particles in which the qualities of a
substance inhere are definite bodies or systems of bodies moving in
space, and that _a lump of sugar is a universe of moving worlds_.

If on a clear night you direct a telescope to one of the many
star-clusters of our northern heavens, you will have presented to the
eye as good a diagram as we can at present draw of what we suppose
would, under certain circumstances, be seen in a lump of sugar if we
could look into the molecular universe with the same facility with
which the telescope penetrates the depths of space.

Do you tell me that the absurdities of Buffon were wisdom when compared
with such wild speculations as these? The criticism is simply what I
expected, and I must remind you that, as I intimated at the outset, this
conception of modern science is in the transition period of which I then
spoke, and, although very familiar to scientific scholars, has not yet
been grasped by the popular mind. I can further only add that, wild as
it may appear, the idea is the growth of legitimate scientific
investigation, and express my conviction that it will soon become as
much a part of the popular belief as those grand conceptions of
astronomy to which I have referred.

Do you rejoin that we can see the suns in a stellar cluster, but can not
even begin to see the molecules? I must again remind you that, in fact,
you only see points of light in the field of the telescope, and that
your knowledge that these points are immensely distant suns is an
inference of astronomical science; and, further, that our knowledge--if
I may so call our confident belief--that the lump of sugar is an
aggregate of moving molecules is an equally legitimate inference of
molecular mechanics, a science which, although so much newer, is as
positive a field of study as astronomy. Moreover, sight is not the only
avenue to knowledge; and, although our material limitations forbid us to
expect that the microscope will ever be able to penetrate the molecular
universe, yet we feel assured that we have been able by strictly
experimental methods to weigh molecular masses and measure molecular
magnitudes with as much accuracy as those of the fixed stars.

Of all forms of matter the gas has the simplest molecular structure,
and, as might be anticipated, our knowledge of molecular magnitudes is
as yet chiefly confined to materials of this class. I have given below
some of the results which have been obtained in regard to the molecular
magnitudes of hydrogen gas, one of the best studied of this class of
substances; and, although the vast numbers are as inconceivable as are
those of astronomy, they can not fail to impress you with the reality of
the magnitudes they represent. I take hydrogen gas for my illustration
rather than air, because our atmosphere is a mixture of two gases,
oxygen and nitrogen, and therefore its condition is less simple than
that of a perfectly homogeneous material like hydrogen. The molecular
dimensions of other substances, although varying very greatly in their
relative values, are of the same order of magnitude as these.[A]

  [A] As some of the readers of this volume may be interested to
      compare these values, we reproduce the "Table of Molecular Data"
      from Professor Clerk Maxwell's lecture on "Molecules," delivered
      before the British Association at Bradford, and published in
      "Nature," September 25, 1873.

      _Molecular Magnitudes at Standard Temperature and Pressure, 0° C.
      and 76 c. m._

      -----------------------+-----------+---------+----------+---------
      RANK ACCORDING TO      | Hydrogen. | Oxygen. | Carbonic | Carbonic
      ACCURACY OF KNOWLEDGE. |           |         |  Oxide.  | Dioxide.
      -----------------------+-----------+---------+----------+---------
      RANK I.                |           |         |          |
      Relative mass          |        1  |     16  |     14   |     22
      Velocity in metres     |           |         |          |
        per second           |    1,859  |    465  |    497   |    396
                             |           |         |          |
      RANK II.               |           |         |          |
      Mean path in ten       |           |         |          |
        billionths (10^{-10})|           |         |          |
        of a metre           |      965  |    560  |    482   |    379
      Collisions each        |           |         |          |
        second--number of    |           |         |          |
        millions             |   17,750  |  7,646  |  9,489   |  9,720
                             |           |         |          |
      RANK III.              |           |         |          |
      Diameter in hundred    |           |         |          |
        billionths (10^{-11})|           |         |          |
        of a metre           |       58  |     76  |     83   |     93
      Mass in ten million    |           |         |          |
        million million      |           |         |          |
        millionths (10^{-25})|           |         |          |
        of a gramme          |       46  |    736  |    644   |  1,012
      -----------------------+-----------+---------+----------+---------

      Number of molecules in one cubic centimetre of every gas is
      nineteen million million million on 19 (10^{18}).

      Two million hydrogen molecules side by side measure a little
      over one millimetre.

_Dimension of Hydrogen Molecules calculated for Temperature of Melting
Ice, and for the Mean Height of the Barometer of the Sea Level:_

  Mean velocity, 6,099 feet a second.
  Mean path, 31 ten-millionths of an inch.
  Collisions, 17,750 millions each second.
  Diameter, 438,000, side by side, measure 1/100 of an inch.
  Mass, 14 (millions^3) weigh 1/1000 of a grain.
  Gas-volume, 311 (millions^3) fill one cubic inch.

To explain how the values here presented were obtained would be out of
place in a popular lecture,[B] but a few words in regard to two or
three of the data are required to elucidate the subject of this lecture.

  [B] _See_ Professor Maxwell's lecture, _loc. cit._; also, Appletons'
      "Cyclopædia," article "Molecules."

First, then, in regard to the mass or weight of the molecules. So far as
their relative values are concerned, chemistry gives us the means of
determining the molecular weights with very great accuracy; but when we
attempt to estimate their weights in fractions of a grain--the smallest
of our common standards--we can not expect precision, simply because the
magnitudes compared are of such a different order; and the same is true
of most of the other absolute dimensions, such as the diameter and
volume of the molecules. We only regard the values given in our table as
a very rough estimate, but still we have good grounds for believing that
they are sufficiently accurate to give us a true idea of the order of
the quantities with which we are dealing; and it will be seen that,
although the numbers required to express the relations to our ordinary
standards are so large, these molecular magnitudes are no more removed
from us on the one side than are those of astronomy on the other.

Passing next to the velocity of the molecular motion, we find in that a
quantity which, although large, is commensurate with the velocity of
sound, the velocity of a rifle-ball, and the velocities of many other
motions with which we are familiar. We are, therefore, not comparing, as
before, quantities of an utterly different order, and we have confidence
that we have been able to determine the value within very narrow limits
of error. But how surprising the result is! Those molecules of hydrogen
are constantly moving to and fro with this great velocity, and not only
are the molecules of all aëriform substances moving at similar, although
differing rates, but the same is equally true of the molecules of every
substance, whatever may be its state of aggregation.

The gas is the simplest molecular condition of matter, because in this
state the molecules are so far separated from each other that their
motions are not influenced by mutual attractions. Hence, in accordance
with the well-known laws of motion, gas molecules must always move in
straight lines and with a constant velocity until they collide with each
other or strike against the walls of the containing vessel, when, in
consequence of their elasticity, they at once rebound and start on a new
path with a new velocity. In these collisions, however, there is no loss
of motion, for, as the molecules have the same weight and are perfectly
elastic, they simply change velocities, and whatever one may lose the
other must gain.

But, if the velocity changes in this way, you may ask, What meaning has
the definite value given in our table? The answer is, that this is the
mean value of the velocity of all the molecules in a mass of hydrogen
gas under the assumed conditions; and, by the principle just stated, the
mean value can not be changed by the collisions of the molecules among
themselves, however great may be the change in the motion of the
individuals.

In both liquids and solids the molecular motions are undoubtedly as
active as in a gas, but they must be greatly influenced by the mutual
attractions which hold the particles together, and hence the conditions
are far more complicated, and present a problem which we have been able
to solve only very imperfectly, and with which, fortunately, we have not
at present to deal.

Limiting, then, our study to the molecular condition of a gas, picture
to yourselves what must be the condition of our atmosphere, with its
molecules flying about in all directions. Conceive what a molecular
storm must be raging about us, and how it must beat against our bodies
and against every exposed surface. The molecules of our atmosphere move,
on an average, nearly four (3·8) times slower than those of hydrogen
under the same conditions; but then they weigh, on an average, fourteen
and a half times more than hydrogen molecules, and therefore strike with
as great energy. And do not think that the effect of these blows is
insignificant because the molecular projectiles are so small; they make
up by their number for what they want in size.

Consider, for example, a cubic yard of air, which, if measured at the
freezing-point, weighs considerably over two pounds. That cubic yard of
material contains over two pounds of molecules, which are moving with an
average velocity of 1,605 feet a second, and this motion is equivalent,
in every respect, to that of a cannon-ball of equal weight rushing along
its path at the same tremendous rate. Of course, this is true of every
cubic yard of air at the same temperature; and, if the motion of the
molecules of the atmosphere around us could by any means be turned into
one and the same direction, the result would be a hurricane sweeping
over the earth with this velocity--that is, at the rate of 1,094 miles
an hour--whose destructive violence not even the Pyramids could
withstand.

Living as we do in the midst of a molecular tornado capable of such
effects, our safety lies wholly in the circumstance that the storm beats
equally in all directions at the same time, and the force is thus so
exactly balanced that we are wholly unconscious of the tumult. Not even
the aspen-leaf is stirred, nor the most delicate membrane broken; but
let us remove the air from one of the surfaces of such a membrane, and
then the power of the molecular storm becomes evident, as in the
familiar experiments with an air-pump.

As has already been intimated, the values of the velocities both of
hydrogen and of air molecules given above were measured at a definite
temperature, 32° of our Fahrenheit thermometer, the freezing point of
water; and this introduces a very important point bearing on our
subject, namely, that the molecular velocities vary very greatly with
the temperature. Indeed, according to our theory, this very molecular
motion constitutes that state or condition of matter which we call
temperature. A hot body is one whose molecules are moving comparatively
rapidly, and a cold body one in which they are moving comparatively
slowly. Without, however, entering into further details, which would
involve the whole mechanical theory of heat, let me call your attention
to a single consequence of the principle I have stated.

When we heat hydrogen, air, or any mass of gas, we simply increase the
velocity of its moving molecules. When we cool the gas, we simply lessen
the velocity of the same molecules. Take a current of air which enters a
room through a furnace. In passing it comes in contact with heated iron,
and, as we say, is heated. But, as we view the process, the molecules of
the air, while in contact with the hot iron, collide with the very
rapidly oscillating metallic molecules, and fly back as a billiard-ball
would under similar circumstances, with a greatly increased velocity,
and it is this more rapid motion which alone constitutes the higher
temperature.

Consider, next, what must be the effect on the surface. A moment's
reflection will show that the normal pressure exerted by the molecular
storm, always raging in the atmosphere, is due not only to the impact of
the molecules, but also to the reaction caused by their rebound. When
the molecules rebound, they are, as it were, driven away from the
surface in virtue of the inherent elasticity both of the surface and of
the molecules. Now, what takes place when one mass of matter is driven
away from another--when a cannon-ball is driven out of a gun, for
example? Why, the gun _kicks_! And so every surface from which molecules
rebound must _kick_; and, if the velocity is not changed by the
collision, one half of the pressure caused by the molecular bombardment
is due to the recoil. From a heated surface, as we have said, the
molecules rebound with an increased velocity, and hence the recoil must
be proportionally increased, determining a greater pressure against the
surface.

According to this theory, then, we should expect that the air would
press unequally against surfaces at different temperatures, and that,
other things being equal, the pressure exerted would be greater the
higher the temperature of the surface. Such a result, of course, is
wholly contrary to common experience, which tells us that a uniform mass
of air presses equally in all directions and against all surfaces of the
same area, whatever may be their condition. It would seem, then, at
first sight, as if we had here met with a conspicuous case in which our
theory fails. But further study will convince us that the result is just
what we should expect in a dense atmosphere like that in which we dwell;
and, in order that this may become evident, let me next call your
attention to another class of molecular magnitudes.

It must seem strange indeed that we should be able to measure molecular
velocities; but the next point I have to bring to your notice is
stranger yet, for we are confident that we have been able to determine
with approximate accuracy for each kind of gas molecule the average
number of times one of these little bodies runs against its neighbors in
a second, assuming, of course, that the conditions of the gas are given.
Knowing, now, the molecular velocity and the number of collisions a
second, we can readily calculate the mean path of the molecule--that is,
the average distance it moves, under the same conditions, between two
successive collisions. Of course, for any one molecule, this path must
be constantly varying; since, while at one time the molecule may find a
clear coast and make a long run, the very next time it may hardly start
before its course is arrested. Still, taking a mass of gas under
constant conditions, the doctrine of averages shows that the mean path
must have a definite value, and an illustration will give an idea of the
manner in which we have been able to estimate it.

The nauseous, smelling gas we call sulphide of hydrogen has a density
only a little greater than that of air, and its molecules must therefore
move with very nearly as great velocity as the average air
molecule--that is to say, about fourteen hundred and eighty feet a
second; and we might therefore expect that, on opening a jar of the gas,
its molecules would spread instantly through the surrounding atmosphere.
But, so far from this, if the air is quiet, so that the gas is not
transported by currents, a very considerable time will elapse before the
characteristic odor is perceived on the opposite side of an ordinary
room. The reason is obvious: the molecules must elbow their way through
the crowd of air molecules which already occupy the space, and can
therefore advance only slowly; and it is obvious that, the oftener they
come into collision with their neighbors, the slower their progress must
be. Knowing, then, the mean velocity of the molecular motion, and being
able to measure by appropriate means _the rate of diffusion_, as it is
called, we have the data from which we can calculate both the number of
collisions in a second and also the mean path between two successive
collisions. The results, as we must expect, are of the same order as the
other molecular magnitudes. But, inconceivably short as the free[C] path
of a molecule certainly is, it is still, in the case of hydrogen gas,
136 times the diameter of the moving body, which would certainly be
regarded among men as quite ample elbow-room.

  [C] There is an obvious distinction between the free and the
      disturbed path of a molecule, and we can not overlook in
      our calculations the perturbations which the collisions
      necessarily entail. Such considerations greatly complicate
      the problem, which is far more difficult than would appear
      from the superficial view of the subject that can alone be
      given in a popular lecture.

Although, in this lecture, I have as yet had no occasion to mention the
radiometer, I have by no means forgotten my main subject, and everything
which has been said has had a direct bearing on the theory of this
remarkable instrument; and still, before you can understand the great
interest with which it is regarded, we must follow out another line of
thought, converging on the same point.

One of the most remarkable results of modern science is the discovery
that all energy at work on the surface of this planet comes from the
sun. Most of you probably saw, at our Centennial Exhibition, that great
artificial cascade in Machinery Hall, and were impressed with the power
of the steam-pump which could keep flowing such a mass of water. But,
also, when you stood before the falls at Niagara, did you realize the
fact that the enormous floods of water which you saw surging over those
cliffs were in like manner supplied by an all-powerful pump, and that
pump the sun? And not only is this true, but it is equally true that
every drop of water that falls, every wave that beats, every wind that
blows, every creature that moves on the surface of the earth, one and
all, are animated by that mysterious effluence we call the sunbeam. I
say mysterious effluence; for how that power is transmitted over those
92,000,000 miles between the earth and the sun is still one of the
greatest mysteries of Nature.

In the science of optics, as is well known, the phenomena of light are
explained by the assumption that the energy is transmitted in waves
through a medium which fills all space called the luminiferous ether,
and there is no question that this theory of Nature, known in science as
the Undulatory Theory of Light, is, as a working hypothesis, one of the
most comprehensive and searching which the human mind has ever framed.
It has both correlated known facts and pointed the way to remarkable
discoveries. But, the moment we attempt to apply it to the problem
before us, it demands conditions which tax even a philosopher's
credulity.

As sad experience on the ocean only too frequently teaches, energy can
be transmitted by waves as well as in any other way. But every mechanic
will tell you that the transmission of energy, whatever be the means
employed, implies certain well-known conditions. Assume that the energy
is to be used to turn the spindles of a cotton mill. The engineer can
tell you just how many horse-power he must supply for every working-day,
and it is equally true that a definite amount of energy must come from
the sun to do each day's work on the surface of the globe. Further, the
engineer will also tell you that, in order to transmit the power from
his turbine or his steam-engine, he must have shafts and pulleys and
belts of adequate strength, and he knows in every case what is the
lowest limit of safety. In like manner, the medium through which the
energy which runs the world is transmitted must be strong enough to do
the immense work put upon it; and, if the energy is transmitted by
waves, this implies that the medium must have an enormously great
elasticity, an elasticity vastly greater than that of the best-tempered
steel.

But turn now to the astronomers, and learn what they have to tell us in
regard to the assumed luminiferous ether through which all this energy
is supposed to be transmitted. Our planet is rushing in its orbit around
the sun at an average rate of over 1,000 miles a minute, and makes its
annual journey of some 550,000,000 miles in 365 days, 6 hours, 9
seconds, and 6/10 of a second. Mark the tenths; for astronomical
observations are so accurate that, if the length of the year varied
permanently by the tenth of a second, we should know it; and you can
readily understand that, if there were a medium in space which offered
as much resistance to the motion of the earth as would gossamer threads
to a race-horse, the planet could never come up to time, year after
year, to the tenth of a second.

How, then, can we save our theory by which we set so much, and rightly,
because it has helped us so effectively in studying Nature? If we may be
allowed such an extravagant solecism, let us suppose that the engineer
of our previous illustration was the hero of a fairy tale. He has built
a mill, set a steam-engine in the basement, arranged his spindles above,
and is connecting the pulleys by the usual belts, when some stern
necessity requires him to transmit all the energy with cobwebs. Of
course, a good fairy comes to his aid, and what does she do? Simply
makes the cobwebs indefinitely strong. So the physicists, not to be
outdone by any fairies, make their ether indefinitely elastic, and their
theory lands them just here, with a medium filling all space, thousands
of times more elastic than steel, and thousands on thousands of times
less dense than hydrogen gas. There must be a fallacy somewhere, and I
strongly suspect it is to be found in our ordinary materialistic notions
of causation, which involve the old metaphysical dogma, "_nulla actio in
distans_," and which in our day have culminated in the famous apothegm
of the German materialist, "Kein Phosphor kein Gedanke."

But it is not my purpose to discuss the doctrines of causation, and I
have dwelt on the difficulty, which this subject presents in connection
with the undulatory theory, solely because I wished you to appreciate
the great interest with which scientific men have looked for some direct
manifestation of the mechanical action of light. It is true that the
ether waves must have dimensions similar to those of the molecules
discussed above, and we must expect, therefore, that they would act
primarily on the molecules and not on masses of matter. But still the
well-known principles of wave motion have led competent physicists to
maintain that a more or less considerable pressure ought to be exerted
by the ether waves on the surfaces against which they beat, as a partial
resultant of the molecular tremors first imparted. Already, in the last
century, attempts were made to discover some evidence of such action,
and in various experiments the sun's direct rays were concentrated on
films, delicately suspended and carefully protected from all other
extraneous influences, but without any apparent effect; and thus the
question remained until about three years ago, when the scientific world
were startled by the announcement of Mr. Crookes, of London, that, on
suspending a small piece of blackened alder pith in the very perfect
vacuum which can now be obtained with the mercury pump, invented by
Sprengel, he had seen this light body actually repelled by the sun's
rays; and they were still more startled, when, after a few further
experiments, he presented us with the instrument he called a radiometer,
in which the sun's rays do the no inconsiderable work of turning a small
wheel. Let us examine for a moment the construction of this remarkable
instrument.

The moving part of the radiometer is a small horizontal wheel, to the
ends of whose arms are fastened vertical vanes, usually of mica, and
blackened on one side. A glass cap forms the hub, and by the
glass-blower's art the wheel is inclosed in a glass bulb, so that the
cap rests on the point of a cambric needle; and the wheel is so
delicately balanced on this pivot that it turns with the greatest
freedom. From the interior of the bulb the air is now exhausted by means
of the Sprengel pump, until less than 1/1000 of the original quantity is
left, and the only opening is then hermetically sealed. If, now, the
sun's light or even the light from a candle shines on the vanes, the
blackened surfaces--which are coated with lampblack--are repelled, and,
these being symmetrically placed around the wheel, the several forces
conspire to produce the rapid motion which results. The effect has all
the appearance of a direct mechanical action exerted by the light, and
for some time was so regarded by Mr. Crookes and other eminent
physicists, although in his published papers it should be added that Mr.
Crookes carefully abstained from speculating on the subject--aiming, as
he has since said, to keep himself unbiased by any theory, while he
accumulated the facts upon which a satisfactory explanation might be
based.

Singularly, however, the first aspects of the new phenomena proved to be
wholly deceptive, and the motion, so far from being an effect of the
direct mechanical action of the waves of light, is now believed to be a
new and very striking manifestation of molecular motion. To this opinion
Mr. Crookes himself has come, and, in a recent article, he writes:
"Twelve months' research, however, has thrown much light on these
actions, and the explanation afforded by the dynamical theory of gases
makes what was a year ago obscure and contradictory now reasonable and
intelligible."

As is frequently the case in Nature, the chief effect is here obscured
by various subordinate phenomena, and it is not surprising that a great
difference of opinion should have arisen in regard to the cause of the
motion. This would not be an appropriate place to describe the numerous
investigations occasioned by the controversy, many of which show in a
most striking manner how easily experimental evidence may be honestly
misinterpreted in support of a preconceived opinion. I will, however,
venture to trespass further on your patience, so far as to describe the
few experiments by which, very early in the controversy, I satisfied my
own mind on the subject.

When, two years ago, I had for the first time an opportunity of
experimenting with a radiometer, the opinion was still prevalent that
the motion of the wheel was a direct mechanical effect of the waves of
light, and, therefore, that the impulses came from the outside of the
instrument, the waves passing freely through the glass envelope. At the
outset, this opinion did not seem to me to be reasonable, or in harmony
with well-known facts; for, knowing how great must be the molecular
disturbance caused by the sun's rays, as shown by their heating power, I
could not believe that a residual action, such as has been referred to,
would first appear in these delicate phenomena observed by Mr. Crookes,
and should only be manifested in the vacuum of a mercury pump.

On examining the instrument, my attention was at once arrested by the
lampblack coating on the alternate surfaces of the vanes; and, from the
remarkable power of lampblack to absorb radiant heat, it was evident at
once that, whatever other effects the rays from the sun or from a flame
might cause, they must necessarily determine a constant difference of
temperature between the two surfaces of the vanes, and the thought at
once occurred that, after all, the motion might be a direct result of
this difference of temperature--in other words, that the radiometer
might be a small heat engine, whose motions, like those of every other
heat engine, depend on the difference of temperature between its parts.

But, if this were true, the effect ought to be proportional solely to
the heating power of the rays, and a very easy means of roughly testing
this question was at hand. It is well known that an aqueous solution of
alum, although transmitting light as freely as the purest water,
powerfully absorbs those rays, of any source, which have the chief
heating power. Accordingly, I interposed what we call an alum cell in
the path of the rays shining on the radiometer, when, although the light
on the vanes was as bright as before, the motion was almost completely
arrested.

This experiment, however, was not conclusive, as it might still be said
that the _heat_-giving rays acted _mechanically_, and it must be
admitted that the chief part of the energy in the rays, even from the
most brilliant luminous sources, always takes the form of heat. But, if
the action is mechanical, the reaction must be against the medium
through which the rays are transmitted, while, if the radiometer is
simply a heat engine, the action and reaction must be, ultimately at
least, between the heater and the cooler, which in this case are
respectively the blackened surfaces of the vanes and the glass walls of
the inclosing bulb; and here, again, a very easy method of testing the
actual condition at once suggested itself.

If the motion of the radiometer wheel is an effect of mechanical
impulses transmitted in the direction of the beam of light, it was
certainly to be expected that the beam would act on the lustrous as well
as on the blackened mica surfaces, however large might be the difference
in the resultants producing mechanical motion, in consequence of the
great absorbing power of the lampblack. Moreover, since the instrument
is so constructed that, of two vanes on opposite sides of the wheel, one
always presents a blackened and the other a lustrous surface to an
incident beam, we should further expect to find in the motion of the
wheel a differential phenomenon, due to the unequal action of the light
on these surfaces. On the other hand, if the radiometer is a heat
engine, and the reaction takes place between the heated blackened
surfaces of the vanes and the colder glass, it is evident that the total
effect will be simply the sum of the effects at the several surfaces.

In order to investigate the question thus presented, I placed the
radiometer before a common kerosene lamp, and observed, with a
stop-watch, the number of seconds that elapsed during ten revolutions of
the little wheel. Finding that this number was absolutely constant, I
next screened one half of the bulb, so that only the blackened faces
were exposed to the light as the wheel turned them into the beam. Again,
I several times observed the number of seconds during ten turns, which,
although equally constant, was greater than before. Lastly, I screened
the blackened surfaces so that, as the wheel turned, only the lustrous
surfaces of mica were exposed to the light, when, to my surprise, the
wheel continued to turn in the same direction as before, although much
more slowly. It appeared as if the lustrous surfaces were attracted by
the light. Again I observed the time of ten revolutions, and here I have
collected my results, reducing them, in the last column, so as to show
the corresponding number of revolutions in the same time:

  ----------------------+--------------------------+--------------------
       CONDITIONS.      | Time of ten revolutions. | No. of revolutions
                        |                          |   in same time.
  ----------------------|--------------------------|--------------------
  Both faces exposed    |        8 seconds.        |          319
  Blackened faces only  |       11    "            |          232
  Mica faces only       |       29    "            |           88
  ----------------------+--------------------------+--------------------

It will be noticed that 88 + 232 equals very nearly 319. Evidently the
effect, so far from being differential, is concurrent. Hence, the action
which causes the motion must take place between the parts of the
instrument, and can not be a direct effect of impulses imparted by
ether waves; or else we are driven to the most improbable alternative,
that lampblack and mica should have such a remarkable selective power
that the impulses imparted by the light should exert a repulsive force
at one surface and an attractive force at the other. Were there,
however, such an improbable effect, it must be independent of the
thickness of the mica vanes; while, on the other hand, if, as seemed to
us now most probable, the whole effect depended on the difference of
temperature between the lampblack and the mica, and if the light
produced an effect on the mica surface only because, the mica plate
being diathermous to a very considerable extent, the lampblack became
heated through the plate more than the plate itself, then it would
follow that, if we used a thicker mica plate, which would absorb more of
the heat, we ought to obtain a marked difference of effect. Accordingly,
we repeated the experiment with an equally sensitive radiometer, which
we made for the purpose, with comparatively thick vanes, and with this
the effect of a beam of light on the mica surface was absolutely null,
the wheel revolving in the same time, whether these faces were protected
or not.

But one thing was now wanting to make the demonstration complete. A heat
engine is reversible, and if the motion of the radiometer depended on
the circumstance that the temperature of the blackened faces of the
vanes was higher than that of the glass, then by reversing the
conditions we ought to reverse the motion. Accordingly, I carefully
heated the glass bulb over a lamp, until it was as hot as the hand would
bear, and then placed the instrument in a cold room, trusting to the
great radiating power of lampblack to maintain the temperature of the
blackened surfaces of the vanes below that of the glass. Immediately the
wheel began to turn in the opposite direction, and continued to turn
until the temperature of the glass came into equilibrium with the
surrounding objects.

These early experiments have since been confirmed to the fullest extent,
and no physicist at the present day can reasonably doubt that the
radiometer is a very beautiful example of a heat engine, and it is the
first that has been made to work continuously by the heat of the
sunbeam. But it is one thing to show that the instrument is a heat
engine, and quite another thing to explain in detail the manner in which
it acts. In regard to the last point, there is still room for much
difference of opinion, although physicists are generally agreed in
referring the action to the residual gas that is left in the bulb. As
for myself, I became strongly persuaded--after experimenting with more
than one hundred of these instruments, made under my own eye, with every
variation of condition I could suggest--_that the effect was due to the
same cause which determines gas pressure_, and, according to the
dynamical theory of gases, this amounts to saying that the effect is due
to molecular motion. I have not time, however, to describe either my own
experiments on which this opinion was first based, or the far more
thorough investigations since made by others, which have served to
strengthen the first impression.[D] But, after our previous discussions,
a few words will suffice to show how the molecular theory explains the
new phenomena.

  [D] See notice of these investigations by the author of this
      article, in "American Journal of Science and Arts,"
      September, 1877 (3), xiv, 231.

Although the air in the bulb has been so nearly exhausted that less than
the one-thousandth part remains, yet it must be borne in mind that the
number of molecules left behind is by no means inconsiderable. As will
be seen by referring to our table, there must still be no less than
311,000 million million in every cubic inch. Moreover, the absolute
pressure which this residual gas exerts is a very appreciable quantity.
It is simply the one-thousandth of the normal pressure of the
atmosphere, that is, of 14-7/10 pounds on a square inch, which is
equivalent to a little over one hundred grains on the same area. Now,
the area of the blackened surfaces of the vanes of an ordinary
radiometer measures just about a square inch, and the wheel is mounted
so delicately that a constant pressure of one-tenth of a grain would be
sufficient to produce rapid motion. So that a difference of pressure on
the opposite faces of the vanes, equal to one one-thousandth of the
whole amount, is all that we need account for; and, as can easily be
calculated, a difference of temperature of less than half a degree
Fahrenheit would cause all this difference in the pressure of the
rarefied air.

But you may ask, How can such a difference of pressure exist on
different surfaces exposed to one and the same medium? and your question
is a perfectly legitimate one; for it is just here that the new
phenomena seem to belie all our previous experience. If, however, you
followed me in my very partial exposition of the mechanical theory of
gases, you will easily see that on this theory it is a more difficult
question to explain why such a difference of pressure does not manifest
itself in every gas medium and under all conditions between any two
surfaces having different temperatures.

We saw that gas pressure is a double effect, caused both by the impact
of molecules and by the recoil of the surface attending their rebound.
We also saw that when molecules strike a heated surface they rebound
with increased velocity, and hence produce an increased pressure against
the surface, the greater the higher the temperature. According to this
theory, then, we should expect to find the same atmosphere pressing
unequally on equal surfaces if at different temperatures; and the
difference in the pressure on the lampblack and mica surfaces of the
vanes, which the motion of the radiometer wheel necessarily implies, is
therefore simply the normal effect of the mechanical condition of every
gas medium. The real difficulty is, to explain why we must exhaust the
air so perfectly before the effect manifests itself.

The new theory is equal to the emergency. As has been already pointed
out, in the ordinary state of the air the amplitude of the molecular
motion is exceedingly small, not over a few ten-millionths of an inch--a
very small fraction, therefore, of the height of the inequalities on the
lampblack surfaces of the vanes of a radiometer. Under such
circumstances, evidently the molecules would not leave the heated
surface, but simply bound back and forth between the vanes and the
surrounding mass of dense air, which, being almost absolutely a
non-conductor of heat, must act essentially like an elastic solid wall
confining the vanes on either side. For the time being, and until
replaced by convection currents, the oscillating molecules are as much a
part of the vanes as our atmosphere is a part of the earth; and on this
system, as a whole, the homogeneous dense air which surrounds it must
press equally from all directions. In proportion, however, as the air is
exhausted, the molecules find more room and the amplitude of the
molecular motion is increased, and, when a very high degree of
exhaustion is reached, the air particles no longer bound back and forth
on the vanes without change of condition, but they either bound off
entirely like a ball from a cannon, or else, having transferred a
portion of their momentum, return with diminished velocity, and in
either case the force of the reaction is felt.[E]

  [E] The reader will, of course, distinguish between the differential
      action on the opposite faces of the vanes of the radiometer and
      the reaction between the vanes and the glass which are the heater
      and the cooler of the little engine. Nor will it be necessary to
      remind any student that a popular view of such a complex subject
      must be necessarily partial. In the present case we not only meet
      with the usual difficulties in this respect, but, moreover, the
      principles of molecular mechanics have not been so fully developed
      as to preclude important differences of opinion between equally
      competent authorities in regard to the details of the theory. To
      avoid misapprehension, we may here add that, in orderto obtain in
      the radiometer a reaction between the heater and the cooler, it
      is not necessary that the space between them should actually be
      crossed by the moving molecules. It is only necessary that the
      momentum should be transferred across the space, and tide may
      take place along lines consisting of many molecules each. The
      theory, however, shows that such a transfer can only take place
      in a highly rarefied medium. In an atmosphere of ordinary density,
      the accession of heat which the vanes of a radiometer might
      receive from a radiant source would be diffused through the mass
      of the inclosed air. This amounts to saying that the momentum
      would be so diffused, and hence, under such circumstances, the
      molecular motion would not determine any reaction between the
      vanes and the glass envelope. Indeed, a dense mass of gas presents
      to the conduction of heat, which represents momentum, a wall far
      more impenetrable than the surrounding glass, and the diffusion
      of heat is almost wholly brought about by convection currents
      which rise from the heated surfaces. It will thus be seen that
      the great non-conducting power of air comes into play to prevent
      not only the transfer of momentum from the vanes to the glass,
      but also, almost entirely, any direct transfer to the surrounding
      mass of gas. Hence, as stated above, the heated molecules bound
      back and forth on the vanes without change of condition, and the
      mass of the air retains its uniform tension in all parts of the
      bulb, except in so far as this is slowly altered by the convection
      currents just referred to. As the atmosphere, however, becomes
      less dense, the diffusion of heat by convection diminishes, and
      that by molecular motion (conduction) increases until the last
      greatly predominates. When, now, the exhaustion reaches so great
      a degree that the heat, or momentum, is rapidly transferred from
      the heater to the cooler by an exaggeration, or, possibly, a
      modification, of the mode of action we call conduction, then we
      have the reaction on which the motion of the radiometer wheel
      depends.

Thus it appears that we have been able to show by very definite
experimental evidence that the radiometer is a heat engine. We have also
been able to show that such a difference of temperature as the radiation
must produce in the air in _direct_ contact with the opposite faces of
the vanes of the radiometer would determine a difference of tension,
which is sufficient to account for the motion of the wheel. Finally, we
have shown, as fully as is possible in a popular lecture, that,
according to the mechanical theory of gases, such a difference of
tension would have its normal effect only in a highly rarefied
atmosphere, and thus we have brought the new phenomena into harmony with
the general principles of molecular mechanics previously established.

More than this can not be said of the steam-engine, although, of course,
in the older engine the measurements on which the theory is based are
vastly more accurate and complete. But the moment we attempt to go
beyond the general principles of heat engines, of which the steam-engine
is such a conspicuous illustration, and explain how the heat is
transformed into motion, we have to resort to the molecular theory just
as in the case of the radiometer; and the motion of the steam-engine
seems to us less wonderful than that of the radiometer only because it
is more familiar and more completely harmonized with the rest of our
knowledge. Moreover, the very molecular theory which we call upon to
explain the steam-engine involves consequences which, as we have seen,
have been first realized in the radiometer; and thus it is that this new
instrument, although disappointing the first expectations of its
discoverer, has furnished a very striking confirmation of this wonderful
theory. Indeed, the confirmation is so remote and yet so close, so
unexpected and yet so strong, that the new phenomena almost seem to be a
direct manifestation of the molecular motion which our theory assumes;
and when a new discovery thus confirms the accuracy of a previous
generalization, and gives us additional reason to believe that the
glimpses we have gained into the order of Nature are trustworthy, it
excites, with reason, among scientific scholars the warmest interest.

And when we consider the vast scope of the molecular theory, the order
on order of existences which it opens to the imagination, how can we
fail to be impressed with the position in which it places man midway
between the molecular cosmos on the one side and the stellar cosmos on
the other--a position in which he is able, in some measure at least, to
study and interpret both?

Since the time to which we referred at the beginning of this lecture,
when man's dwelling-place was looked at as the center of a creation
which was solely subservient to his wants, there has been a reaction to
the opposite extreme, and we have heard much of the utter insignificance
of the earth in a universe among whose immensities all human belongings
are but as a drop in the ocean. When now, however, we learn from Sir
William Thomson that the drop of water in our comparison is itself a
universe, consisting of units so small that, were the drop magnified to
the size of the earth, these units would not exceed in magnitude a
cricket-ball,[F] and when, on studying chemistry, we still further learn
that these units are not single masses but systems of atoms, we may
leave the illusions of the imagination from the one side to correct
those from the other, and all will teach us the great lesson that man's
place in Nature is not to be estimated by relations of magnitude, but
by the intelligence which makes the whole creation his own.

  [F] "Nature," No. 22, March 31, 1870.

But, if it is man's privilege to follow both the atoms and the stars in
their courses, he finds that, while thus exercising the highest
attributes of his nature, he is ever in the presence of an immeasurably
superior intelligence, before which he must bow and adore, and thus come
to him both the assurance and the pledge of a kinship in which his only
real glory can be found.




V.

MEMOIR OF THOMAS GRAHAM.

    _Reprinted from the "Proceedings of the American Academy
    of Arts and Sciences," Vol. VIII, May 24, 1870._


It would be difficult to find in the history of science a character more
simple, more noble, or more symmetrical in all its parts than that of
Thomas Graham, and he will always be remembered as one of the most
eminent of those great students of nature who have rendered our Saxon
race illustrious. He was born of Scotch parents in Glasgow in the year
1805, and in that city, where he received his education, all his early
life was passed. In 1837 he went to London as Professor of Chemistry in
the newly established London University, now called University College,
and he occupied this chair until the year 1855, when he succeeded Sir
John Herschel as Master of the Royal Mint, a post which he held to the
close of his life. His death, on the 16th of September last (1869), at
the age of sixty, was caused by no active disease, but was simply the
wearing out of a constitution enfeebled in youth by privations
voluntarily and courageously encountered that he might devote his life
to scientific study. As with all earnest students, that life was
uneventful, if judged by ordinary standards; and the records of his
discoveries form the only materials for his biography.

Although one of the most successful investigators of physical science,
the late Master of the Mint had not that felicity of language or that
copiousness of illustration which added so much to the popular
reputation of his distinguished contemporary, Faraday; but his influence
on the progress of science was not less marked or less important. Both
of these eminent men were for a long period of years best known to the
English public as teachers of chemistry, but their investigations were
chiefly limited to physical problems; yet, although both cultivated the
border ground between chemistry and physics, they followed wholly
different lines of research. While Faraday was so successfully
developing the principles of electrical action, Graham with equal
success was investigating the laws of molecular motion. Each followed
with wonderful constancy, as well as skill, a single line of study from
first to last, and to this concentration of power their great
discoveries are largely due.

One of the earliest and most important of Graham's investigations, and
the one which gave the direction to his subsequent course of study, was
that on the diffusion of gases. It had already been recognized that
impenetrability in its ordinary sense is not, as was formerly supposed,
a universal quality of matter. Dalton had not only recognized that
aëriform bodies exhibit a positive tendency to mix, or to penetrate
through each other, even in opposition to the force of gravity, but had
made this quality of gases the subject of experimental investigation. He
inferred, as the result of his inquiry, "that different gases afford no
resistance to each other; but that one gas spreads or expands into the
space occupied by another gas, as it would rush into a vacuum; at least,
that the resistance which the particles of one gas offer to those of
another is of a very imperfect kind, to be compared to the resistance
which stones in the channel of a stream oppose to the flow of running
water." But, although this theory of Dalton was essentially correct and
involved the whole truth, yet it was supported by no sufficient
evidence, and he failed to perceive the simple law which underlies this
whole class of phenomena.

Graham, "on entering on this inquiry, found that gases diffuse into the
atmosphere with different degrees of ease and rapidity." This was first
observed by allowing each gas to diffuse from a bottle into the air
through a narrow tube in opposition to the solicitation of gravity.
Afterward an observation of Doebereiner on the escape of hydrogen gas by
a fissure or crack in a glass receiver caused him to vary the conditions
of his experiments, and led to the invention of the well-known
"diffusion tube." In this simple apparatus a thin septum of plaster of
Paris is used to separate the diffusing gases, which, while it arrests
in a great measure all direct currents between the two media, does not
interfere with the molecular motion. Much later, Graham found in
prepared graphite a material far better adapted to this purpose than the
plaster, and he used septa of this mineral to confirm his early results,
in answer to certain ill-considered criticisms in Bunsen's work on
gasometry. These septa he was in the habit of calling his "atomic
filters."

By means of the diffusion tube, Graham was able to measure accurately
the relative times of diffusion of different gases, and he found that
_equal volumes of any two gases interpenetrate each other in times which
are inversely proportional to the square roots of their respective
densities_; and this fundamental law was the greatest discovery of our
late foreign associate. It is now universally recognized as one of the
few great cardinal principles which form the basis of physical science.

It can be shown, on the principles of pneumatics, that gases should
rush into a vacuum with velocities corresponding to the numbers which
have been found to express their diffusion times; and, in a series of
experiments on what he calls the "_effusion_" of gases, Graham confirmed
by trial this deduction of theory. In these experiments a measured
volume of the gas was allowed to find its way into the vacuous jar
through a minute aperture in a thin metallic plate, and he carefully
distinguished between this class of phenomena and the flowing of gases
through capillary tubes into a vacuum, in which case, however short the
tube, the effects of friction materially modify the result. This last
class of phenomena Graham likewise investigated, and designated by the
term "transpiration."

While, however, it thus appears that the results of Graham's
investigation were in strict accordance with Dalton's theory, it must
also be evident that Graham was the first to observe the exact numerical
relation which obtains in this class of phenomena, and that
all-important circumstance entitles him to be regarded as the discoverer
of the law of diffusion. The law, however, at first enunciated, was
purely empirical, and Graham himself says that something more must be
assumed than that gases are vacua to each other, in order to explain all
the phenomena observed; and according to his original view this
representation of the process was only a convenient mode of expressing
the final result. Such has proved to be the case.

Like other great men, Graham built better than he knew. In the progress
of physical science during the last twenty-five years, two principles
have become more and more conspicuous, until at last they have
completely revolutionized the philosophy of chemistry. In the first
place, it has appeared that a host of chemical as well as of physical
facts are coördinated by the assumption that all substances in the state
of gas have the same molecular volume, or, in other words, contain the
same number of molecules in a given space; and in the second place, it
has become evident that the phenomena of heat are simply the
manifestations of molecular motion. According to this view, the
temperature of a body is the _vis viva_ of its molecules; and, since all
molecules at a given temperature have the same _vis viva_, it follows
that the molecules must move with velocities which are inversely
proportional to the square roots of the molecular weights. Moreover,
since the molecular volumes are equal, and the molecular weights
therefore proportional to the densities of the aëriform bodies in which
the molecules are the active units, it also follows that the velocities
of the molecules in any two gases are inversely proportional to the
square roots of their respective densities. Thus the simple numerical
relations first observed in the phenomena of diffusion are the direct
result of molecular motion; and it is now seen that Graham's empirical
law is included under the fundamental laws of motion. Thus Graham's
investigation has become the basis of the new science of molecular
mechanics, and his measurements of the rates of diffusion prove to be
the measures of molecular velocities.

From the study of diffusion Graham passed by a natural transition to the
investigation of a class of phenomena which, although closely allied to
the first as to the effects produced, differ wholly in their essential
nature. Here also he followed in the footsteps of Dalton. This
distinguished chemist had noticed that a bubble of air separated by a
film of water from an atmosphere of carbonic anhydride gradually
expanded until it burst. In like manner a moist bladder, half filled
with air and tied, if suspended in an atmosphere of the same material,
becomes in time greatly distended by the insinuation of this gas through
its substance. This effect can not be the result of simple diffusion,
for it is to be remembered that the thinnest film of water, or of any
liquid, is absolutely impermeable to a gas as such, and, moreover, only
the carbonic anhydride passes through the film, very little or none of
the air escaping outward. The result depends, first, upon the solution
of the carbonic anhydride by the water on one surface of the film;
secondly, on the evaporation into the air, from the other surface, of
the gas thus absorbed. Similar experiments were made by Drs. Mitchell
and Faust, and others, in which gases passed through a film of
India-rubber, entering into a partial combination with the material on
one surface, and escaping from it on the other.

Graham not only considerably extended our knowledge of this class of
phenomena, but also gave us a satisfactory explanation of the mode in
which these remarkable results are produced. He recognized in these
cases the action of a feeble chemical force, insufficient to produce a
definite compound, but still capable of determining a more or less
perfect union, as in the case of simple solution. He also distinguished
the influence of mass in causing the formation or decomposition of such
weak chemical compounds. The conditions of the phenomena under
consideration are simply these:

First. A material for the septum capable of forming a feeble chemical
union with the gas to be transferred.

Secondly. An excess of the gas on one side of the film and a deficiency
on the other.

Thirdly. Such a temperature that the unstable compound may form at the
surface, where the aëriform constituent is present in large mass, while
it decomposes at the opposite surface, where the quantity is less
abundant.

One of the most remarkable results of Graham's study of this peculiar
mode of transfer of aëriform matter through the very substance of solid
bodies was an ingenious method of separating the oxygen from the
atmosphere. The apparatus consisted simply of a bag of India-rubber kept
distended by an interior framework, while it was exhausted by a Sprengel
pump. Under these circumstances the selective affinity of the caoutchouc
determines such a difference in the rate of transfer of the two
constituents of the atmosphere that the amount of oxygen in the
transpired air rises to forty per cent., and by repeating the process
nearly pure oxygen may be obtained. It was at first hoped that this
method might find a valuable application in the arts, but in this Graham
was disappointed; for the same result has since been effected by purely
chemical methods, which are both cheaper and more rapid.

These experiments on India-rubber naturally led to the study of similar
effects produced with metallic septa, which, although to some extent
previously observed in passing gases through heated metallic tubes, had
been only imperfectly understood. Thus, when a stream of hydrogen or
carbonic oxide is passed through a red-hot iron tube, a no
inconsiderable portion of the gas escapes through the walls. The same is
true to a still greater degree when hydrogen is passed through a red-hot
tube of platinum, and Graham showed that, through the walls of a tube
of palladium, hydrogen gas passes, under the same conditions, almost as
rapidly as water through a sieve. Moreover, our distinguished associate
proved that this rapid transfer of gas through these dense metallic
septa was due, as in the case of the India-rubber, to an actual chemical
combination of its material with the metal, formed at the surface, where
the gas is in excess, and as rapidly decomposed on the opposite face of
the septum. He not only recognized as belonging to this class of
phenomena the very great absorption of hydrogen by platinum plate and
sponge in the familiar experiment of the Doebereiner lamp, but also
showed that this gas is a definite constituent of meteoric iron--a fact
of great interest from its bearing on the meteoric theory.

We are thus led to Graham's last important discovery, which was the
justification of the theory we have been considering, and the crowning
of this long line of investigation. As may be anticipated from what has
been said, the most marked example of that order of chemical compounds,
to which the metallic transpiration of aëriform matter we have been
considering is due, is the compound of palladium with hydrogen. Graham
showed that, when a plate of this metal is made the negative pole in the
electrolysis of water, it absorbs nearly one thousand times its volume
of hydrogen gas--a quantity approximatively equivalent to one atom of
hydrogen to each atom of palladium. He further showed that the metal
thus becomes so profoundly altered as to indicate that the product of
this union is a definite compound. Not only is the volume of the metal
increased, but its tenacity and conducting power for electricity are
diminished, and it acquires a slight susceptibility to magnetism, which
the pure metal does not possess. The chemical qualities of this product
are also remarkable. It precipitates mercury from a solution of its
chloride, and in general acts as a strong reducing agent. Exposed to the
action of chlorine, bromine, or iodine, the hydrogen leaves the
palladium and enters into direct union with these elements. Moreover,
although the compound is readily decomposed by heat, the gas can not be
expelled from the metal by simple mechanical means.

These facts recall the similar relations frequently observed between the
qualities of an alloy and those of the constituent metals, and suggest
the inference made by Graham, that palladium charged with hydrogen is a
compound of the same class--a conclusion which harmonizes with the
theory long held by many chemists, that hydrogen gas is the vapor of a
very volatile metal. This element, however, when combined with
palladium, is in a peculiarly active state, which sustains somewhat the
same relation to the familiar gas that ozone bears to ordinary oxygen.
Hence Graham distinguished this condition of hydrogen by the term
"hydrogenium." Shortly before his death a medal was struck at the Royal
Mint from the hydrogen palladium alloy in honor of its discovery; but,
although this discovery attracted public attention chiefly on account of
the singular chemical relations of hydrogen, which it brought so
prominently to notice, it will be remembered in the history of science
rather as the beautiful termination of a life-long investigation, of
which the medal was the appropriate seal.

Simultaneously with the experiments on _gases_, whose results we have
endeavored to present in the preceding pages, Graham carried forward a
parallel line of investigation of an allied class of phenomena, which
may be regarded as the manifestations of molecular motion in _liquid_
bodies. The phenomena of diffusion reappear in liquids, and Graham
carefully observed the times in which equal weights of various salts
dissolved in water diffused from an open-mouth bottle into a large
volume of pure water, in which the bottle was immersed. He was not,
however, able to correlate the results of these experiments by such a
simple law as that which obtains with gases. It appeared, nevertheless,
that the rate of diffusion differs very greatly for the different
soluble salts, having some relation to the chemical composition of the
salt which he was unable to discover. But he found it possible to divide
the salts into groups of equi-diffusive substances, and he showed that
the rate of diffusion of the several groups bear to one another simple
numerical ratios.

More important results were obtained from the study of a class of
phenomena corresponding to the transpiration of gases through
India-rubber or metallic septa. These phenomena, as manifested in the
transfer of liquids and of salts in solution through bladder or a
similar membrane, had previously been frequently studied under the names
of exosmose and endosmose, but to Graham we owe the first satisfactory
explanation. As in the case of gases, he referred these effects to the
influence of chemical force, combination taking place on one surface of
the membrane and the compound breaking up on the other, the difference
depending, as in the previous instance, on the influence of mass. He
also swept away the arbitrary distinctions made by previous
experimenters, showed that this whole class of phenomena are essentially
similar, and called this manifestation of power simply "osmose."

While studying osmotic action, Graham was led to one of his most
important generalizations--the recognition of the crystalline and
amorphous states as fundamental distinctions in chemistry. Bodies in the
first state he called crystalloids; those in the last state, colloids
(resembling glue). That there is a difference in structure between
crystalloids, like sugar or felspar, and colloids, like barley candy or
glass, has of course always been evident to the most superficial
observer; but Graham was the first to recognize in these external
differences two fundamentally distinct conditions of matter not peculiar
to certain substances, but underlying all chemical differences, and
appearing to a greater or less degree in every substance. He showed that
the power of diffusion through liquids depends very much on these
fundamental differences of condition--sugar, one of the least diffusible
of the crystalloids, diffusing fourteen times more rapidly than caromel,
the corresponding colloid. He also showed that, in accordance with the
general chemical rule, while colloids readily combine with crystalloids,
bodies in the same condition manifest little or no tendency to chemical
union. Hence, in osmose, where the membranes employed are invariably
colloidal, the osmotic action is confined almost entirely to
crystalloids, since they alone are capable of entering into that
combination with the material of the septum on which the whole action
depends.

On the above principles Graham based a simple method of separating
crystalloids from colloids, which he calls "dialysis," and which was a
most valuable addition to the means of chemical analysis. A shallow
tray, prepared by stretching parchment paper (an insoluble colloid) over
a gutta-percha hoop, is the only apparatus required. The solution to be
"dialyzed" is poured into this tray, which is then floated on pure
water, whose volume should be eight or ten times greater than that of
the solution. Under these conditions the crystalloids will diffuse
through the porus septum into the water, leaving the colloids on the
tray, and in the course of a few days a more or less complete separation
of the two classes of bodies will have taken place. In this way
arsenious acid and similar crystalloids may be separated from the
colloidal materials with which, in the case of poisoning, they are
usually found mixed in the animal juices or tissues.

But, besides having these practical applications, the method of dialysis
in the hands of Graham yielded the most startling results, developing an
almost entirely new class of bodies, as the colloidal forms of our most
familiar substances, and justifying the conclusion that the colloidal as
well as the crystalline condition is an almost universal attribute of
matter. Thus, he was able to obtain solutions in water of the colloidal
states of aluminic, ferric, chromic, stannic, metastannic, titanic,
molybdic, tungstic, and silicic hydrates, all of which gelatinize under
definite conditions like a solution of glue. The wonderful nature of
these facts can be thoroughly appreciated only by those familiar with
the subject, but all may understand the surprise with which the chemist
saw such hard, insoluble bodies as flint dissolved abundantly in water
and converted into soft jellies. These facts are, without doubt, the
most important contributions of Dr. Graham to pure chemistry.

In this sketch of the scientific career of our late associate, we have
followed the logical, rather than the chronological, order of events,
hoping thus to render the relations of the different parts of his work
more intelligible. It must be remembered, however, that the two lines of
investigation we have distinguished were in fact inter-woven, and that
the beautiful harmony which his completed life presents was the result,
not of a preconceived plan, but of a constant devotion to truth, and a
childlike faith, which unhesitatingly pressed forward whenever nature
pointed out the way.

Although the investigations of the phenomena connected with the
molecular motion in gases and liquids were by far the most important of
Dr. Graham's labors, he also contributed to chemistry many researches
which can not be included under this head. Of these, which we may regard
as his detached efforts, the most important was his investigation of the
hydrates and other salts of phosphorus. It is true that the
interpretation he gave of the results has been materially modified by
the modern chemical philosophy, yet the facts which he established form
an important part of the basis on which that philosophy rests. Indeed,
it seems as if he almost anticipated the later doctrines of types and
polybasic acids, and in none of his work did he show more discriminating
observation or acute reasoning. A subsequent investigation on the
condition of water in several crystalline salts and in the hydrates of
sulphuric acid is equally remarkable. Lastly, Graham also made
interesting observations on the combination of alcohol with salts, on
the process of etherification, on the slow oxidation of phosphorus, and
on the spontaneous inflammability of phosphureted hydrogen. It would
not, however, be appropriate in this place to do more than enumerate the
subjects of these less important studies; and we have therefore only
aimed in this sketch to give a general view of the character of the
field which this eminent student of nature chiefly cultivated, and to
show how abundant was the harvest of truth which we owe to his faithful
toil.

Graham was not a voluminous writer. His scientific papers were all very
brief, but comprehensive, and his "Elements of Chemistry" was his only
large work. This was an admirable exposition of chemical physics, as
well as of pure chemistry, and gave a more philosophical account of the
theory of the galvanic battery than had previously appeared. Our late
associate was fortunate in receiving during life a generous recognition
of the value of his labors. His membership was sought by almost all the
chief scientific societies of the world, and he enjoyed to a high degree
the confidence and esteem of his associates. Indeed, he was singularly
elevated above the petty jealousies and belittling quarrels which so
often mar the beauty of a student's life, while the great loveliness and
kindliness of his nature closely endeared him to his friends.

In concluding, we must not forget to mention that most genial trait of
Graham's character, his sympathy with young men, which gave him great
influence as a teacher in the college with which he was long associated.
There are many now prominent in the scientific world who have found in
his encouragement the strongest incentive to perseverance, and in his
approval and friendship the best reward of success.




VI.

MEMOIR OF WILLIAM HALLOWES MILLER.

    _Reprinted from the "Proceedings of the American Academy of
    Arts and Sciences," Vol. XVI, May 24, 1881._


William Hallowes Miller, who was elected Foreign Honorary Member of this
Academy in the place of C. F. Naumann, May 26, 1874, died at his
residence in Cambridge, England, on the 20th of May, 1880, at the age of
seventy-nine, having been born at Velindre, in Wales, April 5, 1801. His
life was singularly uneventful, even for a scholar. Graduating with
mathematical honors at Cambridge in 1826, he became a fellow of his
college (St. John's) in 1829, and was elected Professor of Mineralogy in
the University in 1832. Under the influence of the calm and elegant
associations of this ancient English university, Miller passed a long
and tranquil life--crowded with useful labors, honored by the respect
and love of his associates, and blessed by congenial family ties. This
quiet student-life was exactly suited to his nature, which shunned the
bustle and unrest of our modern world. For relaxation, even, he loved to
seek the retired valleys of the Eastern Alps; and the description which
he once gave to the writer, of himself sitting at the side of his wife
amid the grand scenery, intent on developing crystallographic formulæ,
while the accomplished artist traced the magnificent outlines of the
Dolomite mountains, was a beautiful idyl of science.

Miller's activities, however, were not confined to the University. In
1838 he became a Fellow of the Royal Society, and in 1856 he was
appointed its Foreign Secretary--a post for which he was eminently
fitted, and which he filled for many years. In 1843 he was selected one
of a committee to superintend the construction of the new Parliamentary
standards of length and weight, to replace those which had been lost in
the fire which consumed the Houses of Parliament in 1834, and to
Professor Miller was confided the construction of the new standard of
weight. His work on this important committee, described in an extended
paper published in the "Philosophical Transactions" for 1856, was a
model of conscientious investigation and scientific accuracy. Professor
Miller was subsequently a member of a new Royal Commission for
"examining into and reporting on the state of the secondary standards,
and for considering every question which could affect the primary,
secondary, and local standards"; and in 1870 he was appointed a member
of the "Commission Internationale du Mètre." His services on this
commission were of great value, and it has been said that "there was no
member whose opinions had greater weight in influencing a decision upon
any intricate and delicate question."

Valuable, however, as were Professor Miller's public services on these
various commissions, his chief work was at the University. His teacher,
Dr. William Whewell--afterward the Master of Trinity College--was his
immediate predecessor in the Professorship of Mineralogy at Cambridge.
This great scholar, whose encyclopædic mind could not long be confined
in so narrow a field, held the professorship only four years; but during
this period he devoted himself with his usual enthusiasm to the study of
crystallography, and he accomplished a most important work in attracting
to the same study young Miller, who brought his mathematical training to
its elucidation. It was the privilege of Professor Miller to accomplish
a unique work, for the like of which a more advanced science, with its
multiplicity of details, will offer few opportunities.

The foundations of crystallography had been laid long before Miller's
time. Haüy is usually regarded as the founder of the science; for he
first discovered the importance of cleavage, and classed the known facts
under a definite system. Taking cleavage as his guide, and assuming that
the forms of cleavage were not only the _primitive forms_ of crystals as
a whole, but also the forms of their _integrant molecules_, he
endeavored to show that all secondary forms might be derived from a few
primary forms, regarded as elements of nature, by means of _decrements_
of molecules at their edges. In like manner he showed that all the forms
of a given mineral, like fluor-spar or calcite, might be built up from
the integrant molecules by skillfully placing together the primitive
forms. Haüy's dissection of crystals, in a manner which appeared to lead
to their ultimate crystalline elements, gained for his system great
popular attention and applause. The system was developed with great
perspicuity and completeness in a work remarkable for the vivacity of
its style and the felicity of its illustration. Moreover, a simple
mathematical expression was given to the system, and the notation which
Haüy invented to express the relation of the secondary to the primary
forms, as modified and improved by Lèvy, is still used by the French
mineralogists.

The system of Haüy, however, was highly artificial, and only prepared
the way for a simpler and more general expression of the facts. The
German crystallographer, Weiss, seems to be the first to have
recognized the truth that the decrements of Haüy were merely a
mechanical mode of representing the fact that all the secondary faces of
a crystal make intercepts on the edges of the primitive form which are
simple multiples of each other; and, this general conception once
gained, it was soon seen that these ratios could be as simply measured
on the axes of symmetry of the crystal as on the edges of the
fundamental forms; and, moreover, that, when crystal forms are viewed in
their relation to these axes, a more general law becomes evident, and
the artificial distinction between primary and secondary forms
disappears.

Thus became slowly evolved the conception of a crystal as a group of
similar planes symmetrically disposed around certain definite and
obvious systems of axes, and so placed that the intercepts, or
parameters, on these axes bore to each other a simple numerical ratio.
Representing by _a_:_b_:_c_ the ratio of the intercepts of a plane
on the three axes of a crystal of a given substance, then the intercepts
of every other plane of this, or of any other crystal of the same
substance, conform to the general proportion _m_·_a_:_n_·_b_:_p_·_c_,
in which _m_, _n_, _p_ are three simple whole numbers. This simple
notation, devised by Weiss, expressed the fundamental law of
crystallography; and the conception of a crystal as a system of planes,
symmetrically distributed according to this law, was a great advance
beyond the decrements of Haüy, an advance not unlike that of astronomy
from the system of vortices to the law of gravitation. Yet, as the
mechanism of vortices was a natural prelude to the law of Newton, so the
decrements of Haüy prepared the way for the wider views of the German
crystallographers.

Whether Weiss or Mohs contributed most to advance crystallography to its
more philosophical stage, it is not important here to inquire. Each of
these eminent scholars did an important work in developing and diffusing
the larger ideas, and in showing by their investigations that the facts
of nature corresponded to the new conceptions. But to Carl Friedrich
Naumann, Professor at the time in the "Bergakademie zu Freiberg,"
belongs the merit of first developing a complete system of theoretical
crystallography based on the laws of symmetry and axial ratios. His
"Lehrbuch der reinen und angewandten Krystallographie," published in two
volumes at Leipzig in 1830, was a remarkable production, and seemed to
grasp the whole theory of the external forms of crystals. Naumann used
the obvious and direct methods of analytical geometry to express the
quantitative relations between the parts of a crystal; and, although his
methods are often unnecessarily prolix and his notation awkward, his
formulæ are well adapted to calculation, and easily intelligible to
persons moderately disciplined in mathematics.

But, however comprehensive and perfect in its details, the system of
Naumann was cumbrous, and lacked elegance of mathematical form. This
arose chiefly from the fact that the old methods of analytical geometry
were unsuited to the problems of crystallography; but it resulted also
from a habit of the German mind to dwell on details and give importance
to systems of classification. To Naumann the six crystalline systems
were as much realities of nature as were the forms of the integrant
molecules to Haüy, and he failed to grasp the larger thought which
includes all partial systems in one comprehensive plan.

Our late colleague, Professor Miller, on the other hand, had that power
of mathematical generalization which enabled him to properly subordinate
the parts to the whole, and to develop a system of mathematical
crystallography of such simplicity and beauty of form that it leaves
little to be desired. This was the great work of his life, and a work
worthy of the university which had produced the "Principia." It was
published in 1839, under the title, "A Treatise on Crystallography"; and
in 1863 the substance of the work was reproduced in a more perfect form,
still more condensed and generalized, in a thin volume of only
eighty-six pages, which the author modestly called, "A Tract on
Crystallography."

Miller began his study of crystallography with the same materials as
Naumann; but, in addition, he adopted the beautiful method of Franz
Ernst Neumann of referring the faces of a crystal to the surface of a
circumscribed sphere by means of radii drawn perpendicular to the faces.
The points where the radii meet the spherical surface are the poles of
the faces, and the arcs of great circles connecting these poles may
obviously be used as a measure of the angles between the crystal faces.
This invention of Neumann's was the germ of Miller's system of
crystallography, for it enabled the English mathematician to apply the
elegant and compendious methods of spherical trigonometry to the
solution of crystallographic problems; and Professor Miller always
expressed his great indebtedness to Neumann, not only for this simple
mode of defining the position of the faces of a crystal, but also for
his method of representing the relative position of the poles of the
faces on a plane surface by a beautiful application of the methods of
stereo-graphic and gnomonic projection. This method of representing a
crystal shows very clearly the relations of the parts, and was
undoubtedly of great aid to Miller in assisting him to generalize his
deductions.

From the outset, Professor Miller apprehended more clearly than any
previous writer the all-embracing scope of the great law of
crystallography. He opens his treatise with its enunciation, and, from
this law as the fundamental principle of the subject, the whole of his
system of crystallography is logically developed. Beyond this, all that
is peculiar to Miller's system is involved in two or three general
theorems. The rest of his treatise consists of deductions from these
principles and their application to particular cases.

One of the most important of these principles, and one which in the
treatise is involved in the enunciation of the fundamental law of
crystallography, is in its essence nothing but an analytical device.
As we have already stated, Weiss had shown that, if _a_:_b_:_c_
represent the ratio of the intercepts of any plane of a crystal on the
three axes _x_, _y_, and _z_, respectively, the intercepts of any other
possible plane must satisfy the proportion--

  _A_:_B_:_C_ = _m_·_a_:_n_·_b_:_p_·_c_,

in which _m_, _n_, and _p_ are simple whole numbers. The irrational
values _a_, _b_, and _c_ are fundamental magnitudes for every
crystalline substance;[G] and Miller called these relative magnitudes
the parameters of the crystals, while he called the whole numbers, _m_,
_n_, and _p_, the indices of the respective planes. But, instead of
writing the proportion which expresses the law of crystallography as
above, he gave to it a slightly different form, thus:

  _A_:_B_:_C_ = (1/_h_)·_a_:(1/_k_)·_b_:(1/_l_)·_c_,

and used in his system for the indices of a plane the values
_h_:_k_:_l_, which are also in the ratio of whole numbers, and usually
of simpler whole numbers than _m_:_n_:_p_. This seems a small
difference; for _h_ _k_ _l_ in the last proportion are obviously the
reciprocals of _m_ _n_ _p_ in the first; but the difference, small as it
is, causes a wonderful simplification of the formulæ which express the
relations between the parts of a crystal. From the last proportion we
derive at once

  (1/_h_)·(_a_/_A_) = (1/_k_)·(_b_/_B_) = (1/_l_)·(_c_/_C_),

which is the form in which Miller stated his fundamental law.

  [G] For example, the native crystals
        of sulphur have                _a_:_b_:_c_ = 1:2·340:1·233.
      Crystals of gypsum have          _a_:_b_:_c_ = 1:0·413:0·691.
      Crystals of tin-stone have       _a_:_b_:_c_ = 1:1:0·6724.
      And crystals of common salt have _a_:_b_:_c_ = 1:1:1.

If _P_ represents the "pole" of a face whose "indices" are _h_ _k_ _l_,
that is, represents the point where the radius drawn normal to the face
meets the surface of the sphere circumscribed around the crystal (the
sphere of projection, as it is called), and if _X_, _Y_, _Z_ represent
the points where the axes of the crystal meet the same spherical
surface,[H] then it is evident that _X Y_, _X Z_, and _Y Z_ are the
arcs of great circles, which measure the inclination of the axes to each
other, and that _P X_, _P Y_, and _P Z_ are arcs of other great circles,
which measure the inclination of the plane (_h_ _k_ _l_) on planes
normal to the respective axes; and, also, that these several arcs form
the sides of spherical triangles thus drawn on the sphere of projection.
Now, it is very easily shown that

  (_a_/_h_)·cos _P X_ = (_b_/_k_)·cos _P Y_ = (_c_/_l_)·cos _P Z_;

and by means of this theorem we are able to reduce a great many problems
of crystallography to the solution of spherical triangles.

  [H] The origin of the axes is always taken as the center of the
      sphere of projection.

Another very large class of problems in crystallography is based on the
relation of faces in a zone; that is, of faces which are all parallel
to one line called the zone axis, and whose mutual intersections,
therefore, are all parallel to each other. If, now, _h_ _k_ _l_ and
_p_ _q_ _r_ are the indices of any two planes of a zone (not parallel to
each other), any other plane in the same zone must fulfill the condition
expressed by the simple equation

  u·_u_ + v·_v_ + w·_w_ = _o_,

where _u_ _v_ and _w_ are the indices of the third plane, and u v w
have the values

  u = _k_·_r_ - _l_·_q_
  v = _l_·_p_ - _h_·_r_
  w = _h_·_q_ - _k_·_p_.

Since _h_ _k_ _l_ and _p_ _q_ _r_ are whole numbers, it is evident that
u v w must also be whole numbers, and these quantities are called the
indices of the zone. The three whole numbers which are the indices of a
plane when written in succession serve as a very convenient symbol of
that plane, and represent to the crystallographer all its relations; and
in like manner Miller used the indices of a zone inclosed in brackets as
the symbol of that zone. Thus 123, 531, 010 are symbols of planes, and
[111], [213], [001] symbols of zones.

An additional theorem enables us to calculate the symbols of a fourth
plane in a zone when the angular distances between the four planes and
the symbols of three of them are known, but this problem can not be made
intelligible with a few words.

The few propositions to which we have referred involve all that is
essential and peculiar to the system of Professor Miller. These given,
and the rest could be at once developed by any scholar who was familiar
with the facts of crystallography; and the circumstance that its
essential features can be so briefly stated is sufficient to show how
exceedingly simple the system is. At the same time, it is wonderfully
comprehensive, and the student who has mastered it feels that it
presents to him in one grand view the entire scheme of crystal forms,
and that it greatly helps him to comprehend the scheme as a whole, and
not simply as the sum of certain distinct parts. So felt Professor
Miller himself; and, while he regarded the six systems of crystals of
the German crystallographers as natural divisions of the field, he
considered that they were bounded by artificial lines which have no
deeper significance than the boundary lines on a map. How great the
unfolding of the science from Haüy to Miller, and yet now we can see the
great fundamental ideas shining through the obscurity from the first!
What we now call the parameters of a crystal were to Haüy the
fundamental dimensions of his "integrant molecules," our indices were
his "decrements," and our conceptions of symmetry his "fundamental
forms." There has been nothing peculiar, however, in the growth of
crystallography. This growth has followed the usual order of science,
and here as elsewhere the early, gross, material conceptions have been
the stepping-stones by which men rose to higher things. In sciences like
chemistry, which are obviously still in the earlier stages of their
development, it would be well if students would bear in mind this truth
of history, and not attach undue importance to structural formulæ and
similar mechanical devices, which, although useful for aiding the
memory, are simply hindrances to progress as soon as the necessity of
such assistance is passed. And, when the life of a great master of
science has ended, it is well to look back over the road he has
traveled, and, while we take courage in his success, consider well the
lesson which his experience has to teach; and, as progress in this
world's knowledge has ever been from the gross to the spiritual, may we
not rejoice as those who have a great hope?

Although the exceeding merit of the "Treatise on Crystallography" casts
into the shade all that was subordinate, we must not omit to mention
that Professor Miller published an early work on hydrostatics, and
numerous shorter papers on mineralogy and physics, which were all
valuable, and constantly contained important additions to knowledge.
Moreover, the "New Edition of Phillips's Mineralogy," which he published
in 1852 in connection with H. J. Brooke, owed its chief value to a mass
of crystallographic observations which he had made with his usual
accuracy and patience during many years, and there tabulated in his
concise manner. As has been said by one of his associates in the Royal
Society, "it is a monument to Miller's name, although he almost expunged
that name from it."[I] It is due to Professor Miller's memory that his
works should be collated, and especially that by a suitable commentary
his "Tract on Crystallography" should be made accessible to the great
body of the students of physical science, who have not, as a rule, the
ability or training which enables them to apprehend a generalization
when solely expressed in mathematical terms. The very merits of
Professor Miller's book as a scientific work render it very difficult to
the average student, although it only involves the simplest forms of
algebra and trigonometry.

  [I] "Obituary Notices from the Proceedings of the Royal Society,"
      No. 206, 1880, to which the writer has been indebted for
      several biographical details.

Independence, breadth, accuracy, simplicity, humility, courtesy, are
luminous words which express the character of Professor Miller. In his
genial presence the young student felt encouraged to express his
immature thoughts, which were sure to be treated with consideration,
while from a wealth of knowledge the great master made the error evident
by making the truth resplendent. It was the greatest satisfaction to the
inexperienced investigator when his observations had been confirmed by
Professor Miller, and he was never made to feel discouraged when his
mistakes were corrected. The writer of this notice regards it as one of
the great privileges of his youth, and one of the most important
elements of his education, to have been the recipient of the courtesies
and counsel of three great English men of science, who have always been
"his own ideal knights," and these noble knights were Faraday, Graham,
and Miller.




VII.

WILLIAM BARTON ROGERS.


William Barton Rogers was born at Philadelphia, on the 7th of December,
1804. His father, Patrick Kerr Rogers, was a native of Newton Stewart,
in the north of Ireland; but while a student at Trinity College, Dublin,
becoming an object of suspicion on account of his sympathy with the
Rebellion of 1798, he emigrated to this country, and finished his
education in the University of Pennsylvania, at Philadelphia, where he
received the degree of Doctor of Medicine.

Here he married Hannah Blythe, a Scotch lady--who was at the time living
with her aunt, Mrs. Ramsay--and settled himself in his profession in a
house on Ninth Street, opposite to the University; and in this house
William B. Rogers was born. He was the second of four sons--James,
William, Henry, and Robert--all of whom became distinguished as men of
science.

Patrick Kerr Rogers, finding that his prospects of medical practice in
Philadelphia had been lessened in consequence of a protracted absence in
Ireland, made necessary by the death of his father, removed to
Baltimore; but soon afterward accepted the Professorship of Chemistry
and Physics in William and Mary College, Virginia, made vacant by the
resignation of the late Robert Hare; and it is a fact worthy of notice
that, while he succeeded Dr. Hare at William and Mary College, his
eldest son, James, succeeded Dr. Hare at the University of Pennsylvania.
At William and Mary College the four brothers Rogers were educated; and
on the death of the father, at Ellicott Mills, in 1828, William B.
Rogers succeeded to the professorship thus made vacant.

He had already earned a reputation as a teacher by a course of lectures
before the Maryland Institute in Baltimore during the previous year, and
after his appointment at once entered on his career as a scientific
investigator. At this period he published a paper on "Dew," and, in
connection with his brother Henry, another paper on the "Voltaic
Battery"--both subjects directly connected with his professorship. But
his attention was early directed to questions of chemical geology; and
he wrote, while at William and Mary College, a series of articles for
the "Farmer's Register" on the "Green Sands and Marls of Eastern
Virginia," and their value as fertilizers. Next we find the young
professor going before the Legislature of Virginia, and, while modestly
presenting his own discoveries, making them the occasion for urging upon
that body the importance of a systematic geological survey for
developing the resources of the State. So great was the scientific
reputation that Professor Rogers early acquired by such services, that
in 1835 he was called to fill the important Professorship of Natural
Philosophy and Geology in the University of Virginia; and during the
same year he was appointed State Geologist of Virginia, and began those
important investigations which will always associate his name with
American geology.

Professor Rogers remained at the head of the Geological Survey of
Virginia until it was discontinued, in 1842, and published a series of
very valuable annual reports. As was anticipated, the survey led to a
large accumulation of material, and to numerous discoveries of great
local importance. As this was one of the earliest geological surveys
undertaken in the United States, its directors had in great measure to
devise the methods and lay out the plans of investigation which have
since become general. This is not the place, however, for such details;
but there are four or five general results of Professor Rogers's
geological work at this period which have exerted a permanent influence
on geological science, and which should therefore be briefly noticed.
Some of these results were first published in the "American Journal of
Science"; others were originally presented to the Association of
American Geologists and Naturalists, and published in its
"Transactions." Professor Rogers took a great interest in the
organization of this association in 1840, presided over its meeting in
1845, and again, two years later, when it was expanded into the American
Association for the Advancement of Science.

In connection with his brother Robert, Professor William B. Rogers was
the first to investigate the solvent action of water--especially when
charged with carbonic acid--on various minerals and rocks; and by
showing the extent of this action in nature, and its influence in the
formation of mineral deposits of various kinds, he was one of the first
to observe and interpret the important class of facts which are the
basis of chemical geology.

Another important result of Professor Rogers's geological work was to
show that the condition of any coal-bed stands in a close genetic
relation to the amount of disturbance to which the enclosing strata have
been submitted, the coal becoming harder and containing less volatile
matter as the evidence of disturbance increases. This generalization,
which seems to us now almost self-evident--understanding, as we do, more
of the history of the formation of coal--was with Professor Rogers an
induction from a great mass of observed facts.

By far, however, the most memorable contribution of Professor Rogers to
geology was that made in connection with Henry D. Rogers, in a paper
entitled "The Laws of Structure of the more Disturbed Zones of the
Earth's Crust," presented by the two brothers at the meeting of the
Association of American Geologists and Naturalists, held at Boston in
1842. This paper was the first presentation of what may be called in
brief the "Wave Theory of Mountain Chains." This theory was deduced by
the brothers Rogers from an extended study of the Appalachian Chain in
Pennsylvania and Virginia, and was supported by numerous geological
sections and by a great mass of facts. The hypothesis which they offered
as an explanation of the origin of the great mountain waves may not be
generally received; but the general fact, that the structure of mountain
chains is alike in all the essential features which the brothers Rogers
first pointed out, has been confirmed by the observations of Murchison
in the Ural, of Darwin in the Andes, and of the Swiss geologists in the
Alps. "In the Appalachians the wave structure is very simple, and the
same is true in all corrugated districts where the crust movements have
been simple, and have acted in one direction only. But where the
elevating forces have acted in different directions at different times,
causing interference of waves like a chopped sea, as in the Swiss Alps
and the mountains of Wales or Cumberland, the undulations are disguised,
and are with extreme difficulty made out." The wave theory of mountain
chains was the first important contribution to dynamical and structural
geology which had been brought forward in this country. It excited at
the time great interest, as well from the novelty of the views as from
the eloquence with which they were set forth; and to-day it is still
regarded as one of the most important advances in orographic geology.

A marked feature of mountain regions is that rupturing of the strata
called faults; and another of the striking geological generalizations of
the brothers Rogers is what may be called the law of the distribution of
faults. They showed that faults do not occur on gentle waves, but in the
most compressed flexures of the mountain chains, which in the act of
moving have snapped or given way at the summit where the bend is
sharpest, the less inclined side being shoved up on the plane of the
fault, this plane being generally parallel to, if it does not coincide
with, the axis plane; and, further, that "the direction of these faults
generally follows the run of the line of elevation of the mountains, the
length and vertical displacement depending on the strength of the
disturbing force."

The last of the general geological results to which we referred above
was published under the name of William B. Rogers only. It was based on
the observed positions of more than fifty thermal springs in the
Appalachian belt, occurring in an area of about fifteen thousand square
miles, which were shown to issue from anticlinal axes and faults, or
from points very near such lines; and in connection with these springs
it was further shown that there was a great preponderance of nitrogen in
the gases which the waters held in solution.

It must be remembered that, during the time when this geological work
was accomplished, Professor Rogers was an active teacher in the
University of Virginia, giving through a large part of the year almost
daily lectures either on physics or geology. Those who met him in his
after-life in various relations in Boston, and were often charmed by his
wonderful power of scientific exposition, can readily understand the
effect he must have produced, when in the prime of manhood, upon the
enthusiastic youths who were brought under his influence. His
lecture-room was always thronged. As one of his former students writes,
"All the aisles would be filled, and even the windows crowded from the
outside. In one instance I remember the crowd had assembled long before
the hour named for the lecture, and so filled the hall that the
professor could only gain admittance through a side entrance leading
from the rear of the hall through the apparatus-room. These facts show
how he was regarded by the students of the University of Virginia. His
manner of presenting the commonest subject in science--clothing his
thoughts, as he always did, with a marvelous fluency and clearness of
expression and beauty of diction--caused the warmest admiration, and
often aroused the excitable nature of Southern youths to the exhibition
of enthusiastic demonstrations of approbation. Throughout Virginia, and
indeed the entire South, his former students are scattered, who even now
regard it as one of the highest privileges of their lives to have
attended his lectures."

Such was the impression which Professor Rogers left at the University of
Virginia, that, when he returned, thirty-five years later, to aid in the
celebration of the semi-centennial, he was met with a perfect ovation.
Although the memories of the civil war, which had intervened, and
Professor Rogers's known sympathies with the Northern cause, might well
have damped enthusiasm, yet the presence of the highly honored teacher
was sufficient to rekindle the former admiration; and, in the language
of a contemporary Virginia newspaper, "the old students beheld before
them the same William B. Rogers who thirty-five years before had held
them spellbound in his class of natural philosophy; and, as the great
orator warmed up, these men forgot their age; they were again young, and
showed their enthusiasm as wildly as when, in days of yore, enraptured
by his eloquence, they made the lecture-room of the University ring with
their applause."

Besides his geological papers, Professor Rogers published, while at the
University of Virginia, a number of important chemical contributions,
relating chiefly to new and improved methods in chemical analysis and
research. These papers were published in connection with his youngest
brother, Robert E. Rogers, now become his colleague as Professor of
Chemistry and Materia Medica in the University; and such were the
singularly intimate relations between the brothers that it is often
impossible to dissociate their scientific work. Among these were papers
"On a New Process for obtaining Pure Chlorine"; "A New Process for
obtaining Formic Acid, Aldehyde, etc."; "On the Oxidation of the Diamond
in the Liquid Way"; "On New Instruments and Processes for the Analysis
of the Carbonates"; "On the Absorption of Carbonic Acid by Liquids";
besides the extended investigation "On the Decomposition of Minerals and
Rocks by Carbonated and Meteoric Waters," to which we have referred
above. There was also at this time a large amount of chemical work
constantly on hand in connection with the Geological Survey, such as
analyses of mineral waters, ores, and the like. Moreover, while at the
University of Virginia, Professor Rogers published a short treatise on
"The Strength of Materials," and a volume on "The Elements of
Mechanics,"--books which, though long out of print, were very useful
text-books in their day, and are marked by the clearness of style and
felicity of explanation for which the author was so distinguished.

The year 1853 formed a turning-point in Professor Rogers's life. Four
years previously he had married Miss Emma Savage, daughter of Hon. James
Savage, of Boston, the well-known author of the "New England
Genealogical Dictionary," and President of the Massachusetts Historical
Society. This connection proved to be the crowning blessing of his life.
Mrs. Rogers, by her energy, her intelligence, her cheerful equanimity,
her unfailing sympathy, became the promoter of his labors, the ornament
and solace of his middle life, and the devoted companion and support of
his declining years. Immediately after his marriage, June 20, 1849, he
visited Europe with his wife, and was present at the meeting of the
British Association for the Advancement of Science, held that year at
Birmingham, where he was received with great warmth, and made a most
marked impression. Returning home in the autumn, Professor Rogers
resumed his work at the University of Virginia; but the new family
relations which had been established led in 1853 to the transfer of his
residence to Boston, where a quite different, but even a more important,
sphere of usefulness surrounded him. His wide scientific reputation, as
well as his family connection, assured him a warm welcome in the most
cultivated circles of Boston society, where his strength of character,
his power of imparting knowledge, and his genial manners, soon commanded
universal respect and admiration. He at once took an active part in the
various scientific interests of the city. From 1845 he had been a Fellow
of this Academy;[J] and after taking up his residence among us he was a
frequent attendant at our meetings, often took part in our proceedings,
became a member of our Council, and from 1863 to 1869 acted as our
Corresponding Secretary. He took a similar interest in the Boston
Society of Natural History. He was a member, and for many years the
President, of the Thursday Evening Scientific Club, to which he imparted
new life and vigor, and which was rendered by him an important field of
influence. The members who were associated with him in that club will
never forget those masterly expositions of recent advances in physical
science; and will remember that, while he made clear their technical
importance to the wealthy business men around him, he never failed to
impress his auditors with the worth and dignity of scientific culture.

  [J] This notice is reprinted from the Proceedings of the American
      Academy of Arts and Sciences, vol. xviii, 1882-'83.

During the earlier years of his residence in Boston, Professor Rogers
occupied himself with a number of scientific problems, chiefly physical.
He studied the variations of ozone (or of what was then regarded as
ozone) in the atmosphere at the time when this subject was exciting
great attention. He was greatly interested in the improvements of the
Ruhmkorff Coil made by Mr. E. S. Ritchie; and in this connection
published a paper on the "Actinism of the Electric Discharge in Vacuum
Tubes." A study of the phenomena of binocular vision led to a paper
entitled "Experiments disproving by the Binocular Combination of Visual
Spectra Brewster's Theory of Successive Combinations of Corresponding
Points." A paper discussing the phenomena of smoke rings and rotating
rings in liquids appeared in the "American Journal of Science" for 1858,
with the description of a very simple but effective apparatus by which
the phenomena would be readily reproduced. In this paper Professor
Rogers anticipated some of the later results of Helmholtz and Sir
William Thomson. In the same year an ingenious illustration of the
properties of sonorous flames was exhibited to the Thursday Evening
Club above mentioned, in which Professor Rogers anticipated Count
Schafgottsch in the invention of a beautiful optical proof of the
discontinuity of the singing hydrogen flame.

In 1861 Professor Rogers accepted from Governor Andrew the office of
Inspector of Gas and Gas-Meters for the State of Massachusetts, and
organized a system of inspection in which he aimed to apply the latest
scientific knowledge to this work; and in a visit he again made to
Europe in 1864 he presented, at the meeting of the British Association
at Bath, a paper entitled "An Account of Apparatus and Processes for
Chemical and Photometrical Testing of Illuminating Gas."

During this period he gave several courses of lectures before the Lowell
Institute of Boston, which were listened to with the greatest
enthusiasm, and served very greatly to extend Professor Rogers's
reputation in this community. Night after night, crowded audiences,
consisting chiefly of teachers and working-people, were spellbound by
his wonderful power of exposition and illustration. There was a great
deal more in Professor Rogers's presentation of a subject than felicity
of expression, beauty of language, choice of epithets, or significance
of gesture. He had a power of marshaling facts, and bringing them all to
bear on the point he desired to illustrate, which rendered the
relations of his subject as clear as day. In listening to this powerful
oratory, one only felt that it might have had, if not a more useful,
still a more ambitious aim; for less power has moved senates and
determined the destinies of empires.

The interest in Professor Rogers's lectures was not excited solely,
however, by the charm of his eloquence; for, although such was the
felicity of his presentations, and such the vividness of his
descriptions, that he could often dispense with the material aids so
essential to most teachers, yet when the means of illustration were at
his command he showed his power quite as much in the adaptation of
experiments as in the choice of language. He well knew that experiments,
to be effective, must be simple and to the point; and he also knew how
to impress his audience with the beauty of the phenomena and with the
grandeur of the powers of nature. He always seemed to enjoy any elegant
or striking illustration of a physical principle even more than his
auditors, and it was delightful to see the enthusiasm which he felt over
the simplest phenomena of science when presented in a novel way.

We come now to the crowning and greatest work of Professor Rogers's
life, the founding of the Massachusetts Institute of Technology--an
achievement so important in its results, so far-reaching in its
prospects, and so complete in its details, that it overshadows all
else. A great preacher has said that "every man's life is a plan of
God's." The faithful workman can only make the best use of the
opportunities which every day offers; but he may be confident that work
faithfully done will not be for naught, and must trustingly leave the
issue to a higher power. Little did young Rogers think, when he began to
teach in Virginia, that he was to be the founder of a great institution
in the State of Massachusetts; and yet we can now see that the whole
work of his life was a preparation for this noble destiny. The very
eloquence he so early acquired was to be his great tool; his work on the
Geological Survey gave him a national reputation which was an essential
condition of success; his life at the University of Virginia, where he
was untrammeled by the traditions of the older universities, enabled him
to mature the practical methods of scientific teaching which were to
commend the future institution to a working community; and, most of all,
the force of character and large humanity developed by his varied
experience with the world were to give him the power, even in the
conservative State of his late adoption, to mold legislators and men of
affairs to his wise designs.

It would be out of place, as it would be unnecessary, to dwell in this
connection on the various stages in the development of the Institute of
Technology. The facts are very generally known in this community, and
the story has been already well told. The conception was by no means a
sudden inspiration, but was slowly matured out of a far more general and
less specific plan, originating in a committee of large-minded citizens
of Boston, who, in 1859, and again in 1860, petitioned the Legislature
of Massachusetts to set apart a small portion of the land reclaimed from
the Back Bay "for the use of such scientific, industrial, and fine art
institutions as may associate together for the public good." The large
scheme failed; but from the failure arose two institutions which are the
honor and pride of Boston--the Museum of Fine Arts and the Institute of
Technology. In the further development of the Museum of Fine Arts,
Professor Rogers had only a secondary influence; but one of his
memorials to the Legislature contains a most eloquent statement, often
quoted, of the value of the fine arts in education, which attests at
once the breadth of his culture and the largeness of his sympathies.

Although the committee of gentlemen above referred to had failed to
carry out their general plan, yet the discussions to which it gave rise
had developed such an interest in the establishment of an institution to
be devoted to industrial science and education that they determined upon
taking the preliminary steps toward the organization of such an
institution. A sub-committee was charged with preparing a plan; and the
result was a document, written by Professor Rogers, entitled "Objects
and Plan of an Institute of Technology." That document gave birth to the
Massachusetts Institute of Technology, for it enlisted sufficient
interest to authorize the committee to go forward. A charter with a
conditional grant of land was obtained from the Legislature in 1861, and
the institution was definitely organized, and Professor Rogers appointed
President, April 8, 1862. Still, the final plans were not matured, and
it was not until May 30, 1864, that the government of the new
institution adopted the report prepared by its president, entitled
"Scope and Plan of the School of Industrial Science of the Massachusetts
Institute of Technology," which Dr. Runkle has called the "intellectual
charter" of the institution, and which he states "has been followed in
all essential points to this very day." In striking confirmation of what
we have written above, Dr. Runkle further says:

"In this document we see more clearly the breadth, depth, and variety of
Professor Rogers's scientific knowledge, and his large experience in
college teaching and discipline. It needed just this combination of
acquirements and experience to put his conceptions into working shape,
to group together those studies and exercises which naturally and
properly belong to each professional course, and thus enable others to
see the guiding-lines which must direct and limit their work in its
relations to the demands of other departments....

"The experimental element in our school--a feature which has been widely
recognized as characteristic--is undoubtedly due to the stress and
distinctness given to it in the 'Scope and Plan.' In our discipline we
must also give credit to the tact and large-heartedness of Professor
Rogers--in the fact that we are entirely free from all petty rules and
regulations relating to conduct, free from all antagonism between
teachers and students."

The associates of Professor Rogers in this Academy--many of them his
associates also in the Institute of Technology, or in the Society of
Arts, which was so important a feature of the organization--will
remember with what admiration they watched the indefatigable care with
which its ever active president fostered the young life of the
institution he had created. They know how, during the earlier years, he
bore the whole weight of the responsibility of the trust he had
voluntarily and unselfishly assumed for the public good; how, while by
his personal influence obtaining means for the daily support of the
school, he gave a great part of the instruction, and extended a personal
regard to every individual student committed to his charge. They recall
with what wisdom, skill, tact, and patience he directed the increasing
means and expanding scope of the now vigorous institution, overcoming
obstacles, reconciling differences, and ingratiating public favor. They
will never forget how, when the great depression succeeded the unhealthy
business activity caused by the civil war, during which the institution
had its rise, the powerful influence of its great leader was able to
conduct it safely through the financial storm. They greatly grieved
when, in the autumn of 1868, the great man who had accomplished so much,
but on whom so much depended, his nerves fatigued by care and overwork,
was obliged to transfer the leadership to a younger man; and ten years
later were correspondingly rejoiced to see the honored chief come again
to the front, with his mental power unimpaired, and with adequate
strength to use his well-earned influence to secure those endowments
which the increased life of the institution required; and they rejoiced
with him when he was able to transfer to a worthy successor the
completed edifice, well established and equipped--an enduring monument
to the nobility of character and the consecration of talents. They have
been present also on that last occasion, and have united in the
acclamation which bestowed on him the title "Founder and Father
perpetual, by a patent indefeasible." They have heard his feeling but
modest response, and have been rejoicing though tearful witnesses when,
after the final seal of commendation was set, he fell back, and the
great work was done.

We honor the successful teacher, we honor the investigator of Nature's
laws, we honor the upright director of affairs--and our late associate
had all these claims to our regard; but we honor most of all the noble
manhood--and of such make are the founders of great institutions. In
comparison, how empty are the ordinary titles of distinction of which
most men are proud! It seems now almost trivial to add that our
associate was decorated with a Doctor's degree, both by his own
university and also by the University at Cambridge; that he was sought
as a member by many learned societies; that he was twice called to
preside over the annual meetings of the American Association for the
Advancement of Science; and that, at the death of Professor Henry, he
was the one man of the country to whom all pointed as the President of
the National Academy of Science. This last honor, however, was one on
which it is a satisfaction to dwell for a moment, because it gave
satisfaction to Professor Rogers, and the office was one which he
greatly adorned, and for which his unusual oratorical abilities were so
well suited. He was a most admirable presiding officer of a learned
society. His breadth of soul and urbanity of manner insensibly resolved
the discords which often disturb the harmonies of scientific truth. He
had the delicate tact so to introduce a speaker as to win in advance the
attention of the audience, without intruding his own personality; and
when a paper was read, and the discussion closed, he would sum up the
argument with such clearness, and throw around the subject such a glow
of light, that abstruse results of scientific investigation were made
clear to the general comprehension, and a recognition gained for the
author which the shrinking investigator could never have secured for
himself. To Professor Rogers the truth was always beautiful, and he
could make it radiant.

It is also a pleasure to record, in conclusion, that Professor Rogers's
declining years were passed in great comfort and tranquillity, amidst
all the amenities of life; that to the last he had the companionship of
her whom he so greatly loved; and that increasing infirmities were
guarded and the accidents of age warded off with a watchfulness that
only the tenderest love can keep. We delight to remember him in that
pleasant summer home at Newport, which he made so fully in reality as in
name the "Morning-side," that we never thought of him as old, and to
believe that the morning glow which he so often watched spreading above
the eastern ocean was the promise of the fuller day on which he has
entered.




VIII.

JEAN-BAPTISTE-ANDRÉ DUMAS.[K]


Jean-Baptiste-André Dumas was born at Alais, in the south of France,
July 14, 1800. His father belonged to an ancient family, was a man of
culture, and held the position as clerk to the municipality of Alais.
The son was educated at the college of his native place, and appears to
have been destined by his parents for the naval service. But the anarchy
and bloodshed which attended the downfall of the First Empire produced
such an aversion to a military life that his parents abandoned their
plan, and apprenticed him to an apothecary of the town. He remained in
this situation, however, but a short time; for, owing to the same sad
causes, he had formed an earnest desire to leave his home, and, his
parents yielding to his wish, he traveled on foot to Geneva in 1816,
where he had relatives who gave him a friendly welcome, and where he
found employment in the pharmacy of Le Royer.

  [K] Reprinted from the Proceedings of the American Academy of
      Arts and Sciences, vol. xix, 1883-'84.

At that time Geneva was the center of much scientific activity, and
young Dumas, while discharging his duties in the pharmacy, had the
opportunity of attending lectures on botany by M. de Candolle, on
physics by M. Pictet, and on chemistry by M. Gaspard de la Rive; and
from these lectures he acquired an earnest zeal for scientific
investigation. The laboratory of the pharmacy gave him the necessary
opportunities for experimenting, and an observation which he made of the
definite proportions of water contained in various commercial salts,
although yielding no new results, gained for him the attention and
friendship of De la Rive. Soon after we find the young philosopher
attempting to deduce the volumes of the atoms in solid and liquid bodies
by carefully determining their specific gravities, and thus anticipating
a method which thirty years later was more fully developed by Hermann
Kopp.

About this time young Dumas had the good fortune to render an important
service to one of the most distinguished physicians of Geneva, whose
name is associated with the beneficial uses of iodine in cases of
goitre. It had occurred to Dr. Coindet that burned sponge, then
generally used as a remedy for that disease, might owe its efficacy to
the presence of a small amount of iodine; and on referring the question
to Dumas, the young chemist not only proved the presence of iodine in
the sponge, but also indicated the best method of administering what
proved to be almost a specific remedy. It was in connection with this
investigation that Dumas's name first appears in public. The discovery
produced a great sensation, and for many years the manufacture of iodine
preparations brought both wealth and reputation to the pharmacy of Le
Royer.

Soon after, Dumas formed an intimacy with Dr. J. L. Prévost, then
recently returned from pursuing his studies in Edinburgh and Dublin, and
was induced to undertake a series of physiological investigations, which
for a time withdrew him from his strictly chemical studies. Several
valuable papers on physiological subjects were published by Prévost and
Dumas, which attracted the notice of Alexander von Humboldt, who on
visiting Geneva, in 1822, sought out Dumas and awakened in him a desire
to seek a wider field of activity than his present position opened to
him. In consequence he removed to Paris in 1823, where the reputation he
had so deservedly earned at Geneva won for him a cordial reception at
what was then the chief center of scientific study in Europe. La Place,
Berthollet, Vauquelin, Gay-Lussac, Thenard, Alexandre Brongniart,
Cuvier, Geoffroy St. Hilaire, Arago, Ampère, and Poisson, all
manifested their interest in the young investigator. Dumas was soon
appointed Répétiteur de Chimie at the École Polytechnique, and also
Lecturer at the Athenæum, an institution founded and maintained by
public subscription, for the purpose of exciting popular interest in
literature and science; and from this beginning his advancement to the
highest position which a man of science can occupy in France was
extremely rapid.

In 1826 he married Mdlle. Herminie Brongniart, the eldest daughter of
Alexandre Brongniart, the illustrious geologist, an alliance which not
only brought him great happiness, and at the time greatly advanced his
social position, but also in after years made his house one of the chief
resorts of the scientific society of Paris. The many who have shared its
generous hospitality will appreciate how greatly, for more than half a
century, Madame Dumas has aided the work and extended the influence of
her noble husband.

In 1828-'29 Dumas united with Théodore Olivier and Eugène Péclet in
founding the École Centrale des Arts et Manufactures, an institution
which met with great success, and in which, as Professor of Chemistry,
Dumas rendered most efficient service for many years; and in 1878 had
the very good fortune to aid in celebrating the fiftieth anniversary of
his own foundation, and to see it acknowledged as among the most
important and efficient scientific institutions of the world. In 1832
Dumas succeeded Gay-Lussac as Professor at the Sorbonne; in 1835 he
succeeded Thenard at the École Polytechnique; and in 1839 he succeeded
Deyeux at the École de Médecine. Thus before the age of forty he filled
successively, and for some time simultaneously, all the important
professorships of chemistry in Paris except one. This exception was that
of the College of France, with which he was never permanently connected,
although it was there that he delivered his famous course on the History
of Chemical Philosophy, when temporarily supplying the place of Thenard.

Dumas early recognized the importance of laboratory instruction in
chemistry, for which there were no facilities at Paris when he first
came to what was then the center of the world's science; and in 1832
founded a laboratory for research at his own expense. This laboratory,
first established at the Polytechnic School, was removed to the Rue
Cuvier in 1839, where it remained until broken up by the Revolution of
1848. The laboratory was small, and Dumas would receive only a few
advanced students, and these on terms wholly gratuitous. Among these
students were Piria, Stas, Melsens, Leblanc, Lalande, and Lewy, with
whose aid he carried on many of his important investigations. By the
Revolution of 1848 Dumas's activities were for a time diverted into
political channels; but under the Second Empire his laboratory was
re-established at the Sorbonne, and in 1868 was removed to the École
Centrale.

The political episode of Dumas's life was the natural result of an
active mind with wide sympathies, which recognizes in the pressing
demands of society its highest duty. The political and social upheaval
of 1848 seemed at the time to endanger the stability in France of
everything which a cultivated and learned man holds most dear; and Dumas
was not one to consider his own preferences when he felt he could aid in
averting the calamities which threatened his country. Immediately after
the Revolution of February, he accepted a seat in the Legislative
Assembly offered him by the electors of the Arrondissement of
Valenciennes. Shortly afterward the President of the Republic called him
to fill the office of Minister of Agriculture and Commerce. During the
Second Empire he was elevated to the rank of Senator, and shortly after
his entrance into the Senate he became Vice-President of the High
Council of Education. In order to reform the abuses into which many of
the higher educational institutions of Paris had fallen, be accepted a
place in the Municipal Council of Paris, over which he subsequently
presided from 1859 to 1870.

In 1868 Dumas was appointed Master of the Mint of France; but he
retained the office only during a short time, for with the fall of the
Second Empire, in 1870, his political career came to an abrupt
termination. The Senate had ceased to exist, and in the stormy days
which followed, the Municipal Council had naturally changed its
complexion; and even at the Mint, the man who had held such a
conspicuous position under the Imperial government was obliged to vacate
his place. Some years previously he had resigned his professorships
because his official positions were incompatible with his relations as
teacher, and now, at the age of seventy, he found himself for the first
time relieved from the daily routine of official duties, and free to
devote his leisure to the noble work of encouraging research, and thus
promoting the advancement of science. He had reached an age when active
investigation was almost an impossibility, but his commanding position
gave him the opportunity of exerting a most powerful influence, and this
he used with great effect. In early life he had been elected, in 1832, a
member of the Academy of Sciences in succession to Serullas; in 1868 he
had succeeded Flourens as its Permanent Secretary; and in 1875 he was
elected a member of the French Academy as successor to Guizot, a
distinction rarely attained by a man of science.

It was, however, as Permanent Secretary of the Academy of Sciences that
Dumas exerted during the last years of his life his greatest influence.
He was the central figure and the ruling spirit of this distinguished
body. No important commission was complete without him, and on all
public occasions he was the orator of the body, always graceful, always
eloquent. In announcing Dumas's death to the Academy, M. Rolland, the
presiding officer, said:

"Vous savez la part considérable que Dumas prenait à vos travaux et vous
avez bien souvent admiré, comme moi, la haute intelligence et la tact
infini avec lesquels il savait imprimer à nos discussions les formes
modérées et courtoises inhérentes à sa nature et à son caractère. Sous
ce rapport aussi la perte de Dumas est irréparable et crée dans
l'Académie un vide bien difficile à combler. Aussi, longtemps encore
nous chercherons, à la place qu'il occupait au Bureau avec tant
d'autorité, la figure sympathique et vénérée de notre bienaimé
Secrétaire perpétuel."

And while Dumas was still occupying his conspicuous position in the
Academy, one of the most distinguished of his German contemporaries[L]
wrote of him: "An ever-ready interpreter of the researches of others, he
always heightens the value of what he communicates by adding from the
rich stores of his own experience, thus often conveying lights not
noticed even by the authors of those researches."

  [L] A. W. Hofmann, in "Nature," February 6, 1880, to whose admirable
      and extended biography the writer is indebted for much of the
      material with which this notice has been prepared.

When the writer last saw Dumas, in the winter of 1881-'82, the great
chemist had still all the vivacity of youth, and it was difficult to
realize his age. He took a lively interest in all questions of chemical
philosophy, which he discussed with great earnestness and warmth. There
was the same fire and the same exuberance of fancy which had enchanted
me in his lectures thirty years before. At an age when most men hold
speculation in small esteem, I was much struck with his criticism of a
contemporary, who, he said, had no imagination, although he spoke with
the highest praise of his experimental skill. At that time Dumas showed
no signs of impaired strength. But during the following year his health
began to fail, and he died on the 11th of April, at Cannes, where he had
sought a retreat from the severity of the winter climate of Paris.

Dumas was one of the few men whose greatness can not be estimated from a
single point of view. He was not only eminent as an investigator of
nature, but even more eminent as a teacher and an administrator.
Beginning the study of chemistry at the culmination of the epoch of the
Lavoisierian system, and regarding, as he always did, the author of
that system with the greatest admiration, he nevertheless was the first
to discover the weak point in its armor and inflict the wound which led
to its overthrow. Without attempting to detail Dumas's numerous
contributions to chemical knowledge, we will here only refer to three
important investigations, which produced a marked influence in the
progress of chemical science.

While still in Geneva, Dumas, as has been said, made numerous
determinations of the densities of allied substances, with a view to
discovering the relations of what he called their molecular or atomic
volumes; and it is no wonder to us that the problem proved too complex
to be solved at that time. After his removal to Paris he took up the
much simpler problem which the relations of the molecular volumes of
aëriform substances present, and his paper "On Some Points of the Atomic
Theory," which was published in the "Annales de Chimie et de Physique"
for 1826, had an important influence in developing our modern chemical
philosophy. Gay-Lussac had previously observed, not only that the
relative weights of the several factors and products concerned in a
chemical process bear to each other definite proportions, but also that,
when the materials are aëriform, the relative volumes preserve an
equally definite and still simpler ratio. Moreover, on the physical
side, Avogadro, and afterward Ampère, had conceived the theory, that in
the state of gas all molecules must have the same volume. It was Dumas
who first saw that these principles furnished an important means of
verifying the molecular and atomic weights.

"I am engaged," he writes, "in a series of experiments intended to fix
the atomic weights of a considerable number of bodies, by determining
their density in the state of gas or vapor. There remains in this case
but one hypothesis to be made, which is accepted by all physicists. It
consists in supposing that, in all elastic fluids observed under the
same conditions, the molecules are placed at equal distances, i. e.,
that they are present in them in equal numbers. An immediate consequence
of this mode of looking at the question has already been the subject of
a learned discussion on the part of Ampère"--and Avogadro, as the author
subsequently adds--"to which, however, chemists, with the exception
perhaps of M. Gay-Lussac, appear to have given as yet but little
attention. It consists in the necessity of considering the molecules of
the simplest gases as capable of a further division--a division
occurring in the moment of combination, and varying with the nature of
the compound."

Here, it is obvious, are the very conceptions which form the basis of
our modern chemical philosophy; and at first we are surprised that they
did not lead Dumas at once to the full realization of the consequences
which the doctrine of equal molecular volumes involves in the
interpretation of the constitution of chemical compounds, and to the
clear distinction between "the physically smallest particles" and "the
chemically smallest particles," or the molecules and the atoms, as we
now call the physical and the chemical units. This distinction is
implied throughout Dumas's paper already quoted, and is illustrated by a
striking example in the introduction to his treatise on "Chemistry
applied to the Arts," published two years later; but the ground was not
yet prepared to receive the seed, and more than a quarter of a century
must pass before the full harvest of this fruitful hypothesis could be
reaped.

There were, however, two important incidental results of this
investigation from which chemical science immediately profited. One was
a simple method of determining with accuracy the vapor densities of
volatile substances which has since been known by Dumas's name. The
other was a radical change in the formula of the silicates. On the
authority of Berzelius, who based his opinion chiefly on the analogy
between the silicates and the sulphates, the formula SiO_{3}, had been
accepted as representing the constitution of silica. But from the
density of both the chloride and the fluoride of silicon Dumas concluded
that the formula was SiO_{2}, a conclusion which is now seen to be in
complete harmony with the scheme of allied compounds. To Berzelius,
however, the new views appeared wholly out of harmony with the system of
chemistry which he had so greatly assisted in developing, and he opposed
them with the whole weight of his powerful influence, and so far
succeeded as to prevent their general adoption for many years. Still,
"the new mode of looking at the constitution of silicic acid slowly but
surely gained ground, and it is now so firmly rooted in our convictions,
that the younger generation of chemists will scarcely understand the
pertinacity with which this innovation was resisted."[M]

  [M] Hofmann, _loc. cit._

But if this investigation of gas and vapor densities brought a great
strain upon the dualistic system, the second of the three great
investigations of Dumas, to which we have referred, led to its complete
overthrow. The experimental results of this investigation would not be
regarded at the present day as remarkable, and can not be compared
either in breadth or intricacy with the results of numerous
investigations of a similar character which have since been made. The
most important of these results were the substitution products obtained
by the action of chlorine gas on acetic acid. They were published in a
series of papers entitled "Sur les Types Chimiques," and the capital
point made was that chlorine could be substituted in acetic acid for a
large part of the hydrogen without destroying the acid relations of the
product; and the inference was, that the qualities of a compound
substance depend not simply on the nature of the elements of which it
consists, but also on the manner or type according to which these
elements are combined.

To the chemists of the present day these results and inferences seem so
natural that it is difficult to understand the spirit with which they
were received forty years ago. But it must be remembered that at that
time the conceptions of chemists were wholly molded in the dualistic
system. It was thought that chemical action depended upon the antagonism
between metals and metalloids, bases and acids, acid salts and basic
salts, and that the qualities of the products resulted from the blending
of such opposite virtues. That chlorine should unite with hydrogen was
natural, for no two substances could be more unlike; but that chlorine
should supply the place of hydrogen in a chemical compound was a
conception which the dualists scouted as absurd. Even Liebig, the
"father of organic chemistry," warmly controverted the interpretation
which Dumas had given to the facts he had discovered. Liebig himself had
successfully investigated the chemical relations of a large class of
organic products. He had, however, worked on the lines of the dualistic
system, showing that organic substances might be classed with similar
inorganic substances, if we assume that certain groups of atoms, which
he called "compound radicals," might take the place of elementary
substances. In the edition of the organic part of Turner's "Chemistry"
bearing his name, organic chemistry is defined as the "chemistry of
compound radicals," and the formulas of organic compounds are
represented on the dualistic system. Liebig's conceptions were therefore
naturally opposed to those advanced by Dumas; but it is pleasant to know
that the controversy which arose never disturbed the friendly relations
between these two noble men of science, who could approach the same
truth from different sides, and yet have faith that each was working for
the same great end. In his commemorative address on Pelouze, Dumas
expresses toward Liebig sentiments of affectionate regard, and Liebig
dedicates to Dumas, with equal warmth, the German edition of his
"Letters on Chemistry."

By the second investigation, as by the first, although Dumas gave a most
fruitful conception to chemistry, he only took the first step in
developing it. His conception of chemical types was very indefinite, and
Laurent wrote of it, a few years later: "Dumas's theory is too general;
by its poetic coloring, it lends itself to false interpretations; it is
a programme of which we await the realization." Laurent himself helped
toward this realization, and in his early death left the work to his
associate and friend Gerhardt, who pushed it forward with great zeal,
classifying chemical compounds according to the four types of
hydrochloric acid, water, ammonia, and marsh-gas. Hofmann, Williamson,
Wurtz, and many others, greatly aided in this work by realizing many of
the possibilities which these types suggested; and thus modern
Structural Chemistry gradually grew up, in which the types of Dumas and
Gerhardt have been in their turn superseded by the larger views which
the doctrine of quantivalence has opened out to the scientific
imagination. It is a singular fact, however, that, while the growth
began in France, the harvest has been chiefly reaped by Germans; and
that, although in its inception the movement was strongly opposed in
Germany, its legitimate conclusions are now repudiated by the most
influential school of French chemists.

The third great investigation of Dumas was his revision of the atomic
weights of many of the chemical elements, and in none of his work did
he show greater experimental skill. His determination of the atomic
weight of oxygen by the synthesis of water, and of that of carbon by the
synthesis of carbonic dioxide, are models of quantitative experimental
work. To this investigation, as to all his other work, Dumas was
directed by his vivid scientific imagination. In his teaching, from the
first, he had aimed to exhibit the relations of the elementary
substances by classing them in groups of allied bodies; and at the
meeting of the British Association in 1851 he had delighted the chemical
section by the eloquence and force with which he exhibited such
relations, especially triads of elementary substances; such as chlorine,
bromine, and iodine; oxygen, sulphur, and selenium; phosphorus, arsenic,
and antimony; calcium, barium, and strontium: in which not only the
atomic weight, but also the qualities of the middle member of the triad,
were the mean of those of the other two members. Later, he came to
regard these triads as parts of more extended series, in each of which
the atomic weights increased from the first to the last element of the
series, by determinate, but not always by equal differences, the values
being, if not exact multiples of the hydrogen atom according to the
hypothesis of Prout, at least multiples of one half or one quarter of
that weight. There can be no doubt that these speculations were more
fanciful than sound, and that Dumas did not do full justice to earlier
theories of the same kind; but with him these speculations were merely
the ornaments, not the substance of his work, and they led him to fix
more accurately the constants of chemistry, and thus to lay a
trustworthy foundation upon which the superstructure of science could
safely be built.

That exuberance of fancy to which we have referred made Dumas one of the
most successful of teachers, and one of the most fascinating of
lecturers. It was the privilege of the writer to attend the larger part
of two of his courses of lectures given in Paris, in the winters of 1848
and 1851, and he remembers distinctly the impression produced. Besides
the well-arranged material and the carefully prepared experiment, there
was an elegance and pomp of circumstance which added greatly to the
effect. The large theatre of the Sorbonne was filled to overflowing long
before the hour. The lecturer always entered at the exact moment, in
full evening dress, and held to the end of a two hours' lecture the
unflagging attention of his audience. The manipulations were entirely
left to the care of a number of assistants, who brought each experiment
to a conclusion at the exact moment when the illustration was required.
An elegance of diction, an appropriateness of illustration, and a
beauty of exposition, which could not be excelled, were displayed
throughout, and the enthusiasm of a French audience added to the
animation of the scene.

To the writer the lectures of Dumas were brought in contrast to those of
Faraday. Both were perfect of their kind, but very different. Faraday's
method was far more simple and natural, and he excelled Dumas in
bringing home to young minds abstruse truths by the logic of
well-arranged consecutive experiment. With Dumas there was no attempt to
popularize science; he excelled in clearness and elegance of exposition.
He exhausted the subject which he treated, and was able to throw a glow
of interest around details which by most teachers would have been made
dry and profitless.

Two volumes of Dumas's lectures have been published; one comprises his
course on the "Philosophy of Chemistry," delivered at the College of
France in 1836; the other contains only a single lecture, accompanied by
notes, entitled "The Balance of Organic Life," which was delivered at
the Medical School of Paris, August 20, 1841. In both these volumes will
be found the beauty of exposition and the elegance of diction of which
we have spoken, and they are models of literary style. But of course the
sympathetic enthusiasm of the great man's presence can not be reproduced
by written words.

The lecture on "The Balance of Organic Life" was probably the most
remarkable of Dumas's literary efforts. It dealt simply with the
relations which the vegetable sustains to the animal kingdom through the
atmosphere, which, though now so familiar, were then not generally
understood; and the late Dr. Jeffries Wyman, who heard the lecture,
always spoke of it with the greatest enthusiasm.

As might be expected, Dumas's oratory found an ample field in the
Chamber of Deputies and in the Senate; and whether setting forth a
project of recasting the copper coinage or a law of drainage, or
ridiculing the absurd theories of homoeopathy, he riveted the
attention of his colleagues as completely as he had entranced the
students at the Sorbonne.

In the early part of his life, Dumas was a voluminous writer, and in
1828 published the "Traité de Chimie appliquée aux Arts," in eight large
octavo volumes, with an atlas of plates in quarto. But besides this
extended treatise, the two volumes of lectures just referred to are his
only important literary works. He published numerous papers in
scientific journals, which, as we have seen, produced a most marked
effect on the growth of chemical science. But the number of his
monographs is not large compared with those of many of his
contemporaries, and his work is to be judged by its importance and
influence rather than by the extent of the field which it covers.

In his capacity of President of the Municipal Council at Paris, of
Minister of Agricultural Commerce, of Vice-President of the High Council
of Education, and of Perpetual Secretary of the Academy of Sciences,
Dumas had abundant opportunity for the exercise of his administrative
ability, and no one has questioned his great powers in this direction;
but in regard to his political career we could not expect the same
unanimity of opinion. That he was a liberal under Louis Philippe, and a
reactionist under Louis Napoleon, may possibly be reconciled with a
fixed political faith and an unswerving aim for the public good; but his
scheme for "civilian billeting" (by which wealthy people having rooms to
spare in their houses would have been compelled to billet artisans
employed in public works) leads one to infer that his statesmanship was
not equal to his science. Nevertheless, there can be no question about
his large-hearted charity. He instituted the "Crédit Foncier," which
flourishes in great prosperity to this day; he also founded the "Caisse
de Rétraite pour la Vieillesse," and several other agricultural
charities, which, though less successful, afford great assistance to
aged workmen. Louis Napoleon used to say in jest that the whole of the
War Minister's budget would not have been enough to realize M. Dumas's
benevolent schemes; and once, half-dazzled, half-amused, by one of the
chemist's vast sanitary projects, he called him "the poet of hygiene."

It was to be expected that a man working with such eminent success in so
many spheres of activity, and at one of the chief centers of the world's
culture, should be loaded with medals, and marks of distinction of every
kind. It would be idle to enumerate the orders of knighthood, or the
learned societies, to which he belonged, for, so far from their honoring
him, he honored them in accepting their membership. It is a pleasure,
however, to remember that he lived to realize his highest ambitions and
to enjoy the fruits of his well-earned renown. France has added his name
in the Pantheon

  "AUX GRANDS HOMMES LA PATRIE RECONNAISSANTE."




IX.

THE GREEK QUESTION.[N]


The question whether the college faculty ought to continue to insist on
a limited study of the ancient Greek language, as an essential
prerequisite of receiving the A. B. degree, has been under consideration
at Cambridge for a long time; and, since the opinions of those with whom
I naturally sympathize have been so greatly misrepresented in the
desultory discussion which has followed Mr. Adams's Phi Beta Kappa
oration, I am glad of the opportunity to say a few words on the "Greek
question."

  [N] Remarks made at the dinner of the Harvard Club of Rhode
      Island, Newport, August 25, 1883.

This question is by no means a new one. For the last ten years it has
been under discussion at most, if not at all, of the great universities
of the world; and, among others, the University of Berlin, which stands
in the very front rank, has already conceded to what we may call the new
culture all that can reasonably be asked.

Let me begin by asserting that the responsible advocates of an expansion
of the old academic system do not wish in the least degree to diminish
the study of the Greek language, the Greek literature, or the Greek art.
On the contrary, they wish to encourage such studies by every legitimate
means. For myself I believe that the old classical culture is the best
culture yet known for the literary professions; and among the literary
professions I include both law and divinity. Fifty years ago I should
have said that it was the only culture worthy of the recognition of a
university. But we live in the present, not in the past, and a
half-century has wholly changed the relations of human knowledge. Regard
the change with favor or disfavor, as you please, the fact remains that
the natural sciences have become the chief factors of our modern
civilization; and--which is the important point in this connection--they
have given rise to new professions that more and more every year are
opening occupations to our educated men. The professions of the chemist,
of the mining engineer, and of the electrician, which have entirely
grown up during the lifetime of many here present, are just as "learned"
as the older professions, and are recognized as such by every
university. Moreover, the old profession of medicine, which, when, as
formerly, wholly ruled by authority or traditions, might have been
classed with the literary professions, has come to rest on a purely
scientific basis.

In a word, the distinction between the literary and the scientific
professions has become definite and wide, and can no longer be ignored
in our systems of education. Now, while they would accord to their
classical associates the right to decide what is the best culture for a
literary calling, the scientific experts claim an equal right to decide
what is the best culture for a scientific calling. Ever since the
revival of Greek learning in Europe the literary scholars have been
working out an admirable system of education. In this system most of us
have been trained. I would pay it all honor, and I would here bear my
testimony to the acknowledged facts that in no departments of our own
university have the methods of teaching been so much improved during the
last few years as in the classical. I should resist as firmly as my
classical colleagues any attempt to emasculate the well-tried methods of
literary culture, and I have no sympathy whatever with the opinion that
the study of the modern languages as polite accomplishments can in any
degree take the place of the critical study of the great languages of
antiquity. To compare German literature with the Greek, or, what is
worse, French literature with the Latin, as means of culture, implies,
as it seems to me, a forgetfulness of the true spirit of literary
culture.

But literature and science are very different things, and "what is one
man's meat may be another man's poison," and the scientific teachers
claim the right to direct the training of their own men. It is not their
aim to educate men to clothe thought in beautiful and suggestive
language, to weave argument into correct and persuasive forms, or to
kindle enthusiasm by eloquence. But it is their object to prepare men to
unravel the mysteries of the universe, to probe the secrets of disease,
to direct the forces of nature, and to develop the resources of this
earth. These last aims may be less spiritual, lower on your arbitrary
intellectual scale, if you please, than the first; but they are none the
less legitimate aims which society demands of educated men: and all we
claim is that the astronomers, the physicists, the chemists, the
biologists, the physicians, and the engineers, who have shown that they
are able to answer these demands of society, should be intrusted with
the training of those who are to follow them in the same work.

Now, such is the artificial condition of our schools, and so completely
are they ruled by prescription, that, when we attempt to lay out a
proper course of training for the scientific professions, we are met at
the very outset by the Greek question. Greek is a requisition for
admission to college, and the only schools in which a scientific
training can be had do not teach Greek, and, what is more, can not be
expected to teach it.

This brings us to the root of the whole difficulty with which the
teachers of natural science have been contending, and which is the cause
of the present movement. We can not obtain any proper scientific
training from the classical schools, and the present requisitions for
admission to college practically exclude students prepared at any
others. At Cambridge we have vainly tried to secure some small measure
of scientific training in the classical schools: first, by establishing
summer courses in practical science especially designed for training
teachers, and chiefly resorted to by such persons; and, secondly, by
introducing some science requisitions into the admission examinations.
But the attempt has been an utter failure. The science requisitions have
been simply "crammed," and the result has been worse than useless;
because, instead of securing any training in the methods of science, it
has in most cases given a distaste for the whole subject. True
science-teaching is so utterly foreign to all their methods that the
requisitions have merely hampered the classical schools, and the sooner
they are abandoned the better. Both the methods and the spirit of
literary and scientific culture are so completely at variance that we
can not expect them to be successfully united in the same preparatory
school.

We look, therefore, to entirely different schools for the two kinds of
preparation for the university which modern society demands--schools,
which for the want of better distinctive names, we may call classical
and scientific schools. In the classical school the aim should be, as it
has always been, literary culture, and the end should be that power of
clothing thought in words which awakens thought. Of course, the results
of natural science must to a certain extent be taught; for even literary
men can not afford to be wholly ignorant of the great powers that move
the world. But the natural sciences should be studied as useful
knowledge, not as a discipline, and such teaching should not be
permitted in the least degree to interfere with the serious business of
the place. In the scientific school, on the other hand, while language
must be taught, it should be taught as a means, not as an end. The
educated man of science must command at least French and German--and for
the present a limited amount of Latin--as well as his mother-tongue,
because science is cosmopolitan. But these languages should be acquired
as tools, and studied no further than they are essential to the one
great end in view, that knowledge which is the essential condition of
the power of observing, interpreting, and ruling natural phenomena.

In such a course as this it is obvious that the study of Greek would
have no place, even if there were time to devote to it, and we can not
alter the appointed span of human life, even out of respect to this most
honored and worthy representative of the highest literary culture. Of
course, no one will question that the scholar who can command both the
literary and scientific culture will be thereby so much the stronger and
more useful man; and certainly let us give every opportunity to the
"double firsts" to cultivate all their abilities, and so the more
efficiently to benefit the world. But such powers are rare, and the
great body of the scientific professions must be made up of men who can
only do well the special class of work in which they have been trained;
and, if you make certain formal and arbitrary requisitions, like a small
amount of Greek, obstacles in the way of their advancement, or of that
social recognition to which they feel themselves entitled as educated
men, those requisitions must necessarily be slighted, and your policy
will give rise to that cry of "fetich" of which recently we have heard
so much.

Now, all the schools which prepare students for Harvard College are
classical schools. We do not wish to alter these schools in any respect,
unless to make them more thorough in their special work. As I have
already said, the small amount of study of natural science which we have
forced upon them has proved to be a wretched failure, and the sooner
this hindrance is got out of their way the better. We do not wish to
alter the studies of such schools as the Boston and Roxbury Latin
Schools, the Exeter and Andover Academies, the St. Paul's and the St.
Mark's Schools, and the other great feeders of the college. No--not in
the least degree! We do not ask for any change which in our opinion will
diminish the number of those coming to the college with a classical
preparation by a single man. We look for our scientific recruits to
wholly different and entirely new sources. For, although we think that
there are many students now coming to us through the classical schools
who would run a better chance of becoming useful men if they were
trained from the beginning in a different way, yet such is the social
prestige of the old classical schools and of the old classical culture
that, whatever new relations might be established, the class of students
which alone we now have would, I am confident, all continue to come
through the old channels.

This is not a mere opinion; for only a very few men avail themselves
of the limited option which we now permit at the entrance
examinations--nine, at least, out of ten, offering what is called
maximum in classics.

We look, then, for no change in the classical schools. Our only
expectation is to affiliate the college with a wholly different class of
schools, which will send us a wholly different class of students, with
wholly different aims, and trained according to a wholly different
method. At the outset we shall look to the best of our New England
high-schools for a limited supply of scientific students, and hope by
constant pressure to improve the methods of teaching in these schools,
as our literary colleagues have within ten years vastly improved the
methods in the classical schools. In time we hope to bring about the
establishment of special academies which will do for science-culture
what Exeter and St. Paul's are doing for classical culture. We expect to
establish a set of requisitions just as difficult as the classical
requisitions--only they will be requisitions which have a different
motive, a different spirit, and a different aim; and all we ask is, that
they should be regarded as the equivalents of the classical requisitions
so far as college standing is concerned. We do not at once expect to
draw many students through these new channels. To improve methods of
teaching and build up new schools is a work of years. But we have the
greatest confidence that in time we shall thus be able to increase very
greatly both the clientage and the usefulness of the university.

Is this heresy? Is this revolution? Is it not rather the scientific
method seeking to work out the best results in education as elsewhere by
careful observation and cautious experimenting, unterrified by authority
or superstition? Certainly, the philologist must respect our method; for
of all the conquests of natural science none is more remarkable than its
conquest of the philologists themselves. They have adopted the
scientific methods as well as the scientific spirit of investigation;
but, while thus widening and classifying their knowledge, they have
rendered the critical study of language more abstruse and more
difficult; and this is the chief reason why the time of preparation for
our college has been so greatly extended during the last twenty-five
years. Nominally, the classical schools cover no more ground than
formerly, but they cultivate that ground in a vastly more thorough and
scientific way.

These increased requirements of modern literary culture suggest another
consideration, which we can barely mention on this occasion. How long
will the condition of our new country permit its youths to remain in
pupilage until the age of twenty-three or twenty-four; on an average at
least three years later than in any of the older countries of the
civilized world? It is all very well that every educated man should have
a certain acquaintance with what have been called the "humanities." But
when your system comes to its present results, and demands of the
physician, the chemist, and the engineer--whose birthright is a certain
social status, which by accident you temporarily control--that he shall
pass fully four years of the training period of his life upon
technicalities, which, however important to a literary man, are
worthless in his future calling, is it not plain that your conservatism
has become an artificial barrier which the progress of society must
sooner or later sweep away? Is it not the part of wisdom, however much
pain it may cost, to sacrifice your traditional preferences gracefully
when you can direct the impending change, and not to wait until the rush
of the stream can not be controlled?




X.

FURTHER REMARKS ON THE GREEK QUESTION.


In a former essay I endeavored to make prominent the essential
difference between a system of education based on scientific culture and
the generally prevailing system which is based on linguistic training. I
maintained that there is not only a difference of subject-matter, but a
difference of method, a difference of spirit, and a difference of aim;
and I argued that, as the conditions of success under the two modes of
culture are so unlike, there was no danger, even with the amplest
freedom, that the study of the physical sciences would supplant or
seriously interfere with linguistic studies. But, although the drift of
my argument was plain, this essay has been quoted in order to show that
not only Greek, but also all linguistic study, would be neglected by the
students of natural science as soon as it ceased to be useful in their
profession; and my attempt to point out a basis of agreement and
co-operation has been made the occasion of reiterating the extreme
doctrine that there can be no liberal education not based on the study
of language. It has been thus assumed that scientific culture can not
supply such a basis, and in this whole discussion the value of the study
of Nature in education, except in so far as this study may yield a fund
of useful knowledge, has been entirely ignored by the advocates of the
old system. Not only has there been no recognition of the value of the
study of material forms and physical phenomena as a mode of liberal
culture, but it has been assumed throughout that--to use the now
familiar form of words--"no sense for conduct" and "no sense for beauty"
can be acquired except through that special type of linguistic training
that has so long limited elementary education. Those who demand a place
for science-culture certainly have not shown the same contemptuous
spirit; and I venture to suggest that, if classical students were as
familiar with the methods of natural science as are the students of
Nature with philological and archæological study, they would be more
charitable to those who differ with them on this subject.

There are, of course, two distinct elements in a liberal education: the
one the acquisition of useful knowledge, the other a training or
culture of the intellectual faculties. The first should be made as broad
as possible, the second, in the present state of knowledge, must
unfortunately be greatly restricted. While in the passage referred to I
have claimed that, in a system of education based upon science,
languages should be studied simply as tools, Mr. Matthew Arnold, in a
lecture which he has recently repeatedly delivered in this country, and
whose constant refrain was the phrases I have already quoted, has
claimed that, although scholars must use the results of science as so
much literary material, they need have nothing to do with its methods.
In my view, both positions are essentially sound. It has been said that
the Greek departments in our colleges could do without the scientific
students much better than scientific scholars could do without Greek,
and this remark admits of an evident rejoinder. Certainly in this age no
professional man can afford to be ignorant of the results of science,
and he will constantly be led into error if he does not know something
of its methods. It is perfectly well known that very few of the
investigators, who have coined the scientific terms derived from the
Greek, so often referred to, could read a page of Herodotus or Homer in
the original; and it is equally true that Mr. Matthew Arnold, and his
compeer, Lord Tennyson, who have shown such large knowledge of the
results of science, could not interpret the complex relations in which
the simplest phenomena of Nature are presented to the observer. The
greater number of the students of Nature can only know the beauties of
Greek literature as they are feebly presented in translations, and so
the greater number of literary students can only know of the wonders of
Nature as they are inadequately described in popular works on science.
If it requires years of study to enable a student to master the meaning
of a Greek sentence, can we expect that in less time a student shall be
able to unravel the intricacies of natural phenomena? It has been said
that no Greek scholarship is possible for a student who begins the study
of that language in college. Is it supposed that scientific scholarship
is any more possible under such conditions?

In order to teach successfully the _results_ of science to college
students, I have no desire that they should have any preliminary
preparation. It has been my duty for more than thirty years to present
the elements of chemistry to the youngest class in one of our colleges,
and I have never had any reason to complain of their want of interest in
the subject. Indeed, I regard it as a great privilege to be the first to
point out to enthusiastic young men the wonderful vistas which modern
science has opened to our view. So far as their temporary interest is
concerned, I should greatly prefer that they had never studied the
subject before coming to college. But even enthusiastic interest in
popular lectures is not scientific culture. A few men in every class
always have been, and will continue to be, so far interested as to make
the cultivation of science the business of their lives. But such men
always labor under the disadvantages resulting from a want of early
training, and these obstacles repel a large number whose natural tastes
and abilities would otherwise have fitted them for a scientific calling.
The change from one system of culture to another, at the age of
eighteen, has all the disadvantages of changing a profession late in
life. Nevertheless, the college will always continue to educate a number
of men of science in this way. Most of these men become teachers, and no
one questions that their previous linguistic training makes them all the
more forcible expositors of scientific truth. It is not for such persons
that I desire any change. I am, however, most anxious that the
university should do its part in educating that important class of men
who are to direct the industries and develop the material resources of
our country. Such men can be led to appreciate, and will give time to
acquire, an elegant use of language, but they will not devote four or
five years of their lives to purely linguistic training, and, if we do
not open our doors to them, they will be forced to content themselves
with such education as high-schools, or, at best, technical schools,
can offer. But, while they will thus lose the broader knowledge and
larger scope which a university education affords, the university will
also lose their sympathy and powerful support. Such students are now
wholly repelled from the university, and, under a more liberal policy,
they would form an important and clear addition to our numbers, and--as
I have said in another place--without diminishing by a single man the
number of those who come to college through the classical schools.

But there is another class of young men with whom a system of education
based on the study of Nature would, as I am convinced, be more
successful than the prevailing system of linguistic culture: I refer to
those who now come to college, some of them through the influence of
family tradition, some of them through the expectation of social
advantage, and a still larger number on account of the attractions of
college-life. Many of these are men who, with poor verbal memories, or
want of aptitude for recognizing abstract relations, can never become
classical scholars with any exertion that they can be expected to make,
but who can often be educated with success through their perceptive
faculties. These men are the dunces of the classical department, they
add nothing to its strength, and in every classical school are a
hindrance to the better students; but some of them may become able and
useful men, if their interest can be aroused in objective realities. Of
our present students, it is only this class that the proposed changes
would really affect. Those who have tastes and aptitudes for linguistic
studies would continue to come through the old channels, and of such
only can classical scholars be made.

I know very well it is said that, although the classical department
would be glad to be rid of this undesirable element, yet the change
could not be made without endangering the continuance of the study of
Greek in many of our classical schools. But can the university be
justified in continuing a requisition which is recognized to be opposed
to the best interests of an important class of its patrons? And
certainly it is not necessary to protect the study of Greek in this
country by any such questionable means. I have a great deal more faith
myself in the value of classical scholarship than many of my classical
colleagues appear to possess. Never has one word of disparagement been
heard from me. I honor true classical scholarship as much as I despise
the counterfeit. To maintain that the class of classical dunces, to whom
I have referred, appreciate the beauties of classical literature or
derive any real advantage from the study is, in my opinion, to maintain
a manifest absurdity. Fully as much do the convicts in a tread-mill
enjoy the beauties of the legal code under which they are compelled to
work; and if, as Chief-Justice Coleridge has recently maintained, in his
speech at New Haven, classical scholarship is the best preparation for
the highest distinctions in church and state, certainly its continuance
does not depend on the minimum requisition in Greek of this
university.[O] The "new culture," although a much "younger industry,"
does not ask for any such artificial protection. It only asks for an
opportunity to show what it can accomplish, and this opportunity it has
never yet had. Even if the largest liberty were granted, those who seek
to promote a genuine education, based on natural science, would labor
under the greatest disadvantages. Not only is the apparatus required for
the new culture far more expensive than that of an ordinary classical
school, but also more personal attention must be given to each scholar,
and the ordinary labor-saving methods of the class-room are wholly
inapplicable. In the face of such obstacles as these conditions present,
the new culture can advance only very gradually; and, amid the rivalry
of the old system, it can only succeed by maintaining a very high degree
of efficiency. The new way will certainly not offer any easier mode of
admission to college than the old; and when it is remembered that the
classical system has the control of all the endowed secondary schools,
the prestige of past success, and the support of the most powerful
social influence, it is difficult to understand on what the opposition
to the free development of the "new education" is based. Are not
gentlemen, who have been talking of a revolution in education, taking
counsel of their fears rather than of their better judgment; and are
they not forgetting that the teachers of natural science have the same
interest in upholding the principles of sound education as have their
classical colleagues? Certainly there can be no question that, in the
future as in the past, they will ever seek to maintain the integrity of
all the great departments of the university unimpaired. It has happened
before this that the judgment, even of intelligent men, has been warped
by their class relations or supposed interests; but as, in this country,
the learned class has no control of government patronage, we may at
least hope that the discussion of the Greek question will never assume
with us the great bitterness that a similar controversy has aroused in
Germany.

  [O] This article was written and read to the Faculty of Harvard
      College shortly after Lord Coleridge's visit to the United
      States, in the autumn of 1883.

There has been a great deal said in this discussion about the
"humanities," and it has been assumed that, while the analysis of the
Greek verb is "humanizing," the analysis of the phenomena of Nature is
"materializing." I can discover nothing humanizing in the one or the
other, except through the spirit with which they are studied, and I know
by experience that the spirit with which the study of the Latin and
Greek grammars is often enforced is most demoralizing. Those who have
been born with a facility for language may laugh at this statement; but
a boy who has been held up to ridicule for the want of a good verbal
memory, denied him by his Creator, long remembers the depressing effect
produced, if not the malignity aroused, by the cruelty. Many are the
men, now eminent in literature as well as science, who have experienced
the tyranny of a classical school, so graphically described in the
Autobiography of Anthony Trollope; and many are the boys who might have
been highly educated if their perceptive faculties had been cultivated,
whose career as scholars has been cut short by the same tyranny.

Again, a great deal has been said about specialization at an early age,
as if the study of Nature were specializing while the study of Latin
metres and Greek accents was liberalizing. But how could specialization
be more strikingly illustrated than by a system which limits a boy's
attention between the ages of twelve and twenty to linguistic studies
to the almost entire exclusion of a knowledge of that universe in which
his life is to be passed, and which so limits his intellectual training
that his powers of observation are left undeveloped, his judgments in
respect to material relations unformed, and even his natural conceptions
of truth distorted? Now, although a special culture which has such
mischievous results as these may be necessary in order to command that
power over language which marks the highest literary excellence, and
although a university should foster this culture by all legitimate
means, yet to enforce it upon every boy who aspires to be a scholar,
whatever may be his natural talents, is as cruel as the Chinese practice
of cramping the feet of women in order to conform to a traditional ideal
of beauty. Indeed, an instructor in natural science has very much the
same difficulty in training classical scholars to observe that a
dancing-master would have in teaching a class of Chinese girls to waltz.

Again, it has been said that while the opportunities for scientific
culture in college are ample, no one will oppose such a modification of
the requisitions for admission as the conditions of this culture demand,
provided only we label the product of such culture with a descriptive
name. Call the product of your scientific culture Bachelors of Science,
we have been told, and you may arrange the requisites of admission to
your own courses as you choose. I am forced to say that this argument,
however specious, is neither ingenuous nor charitable. If you will label
the product of a purely linguistic culture with an equally descriptive
name; if, following the French usage, you will call such graduates
Bachelors of Letters, we shall not object to the term Bachelors of
Science; or, without making so great an innovation, I, for one, should
have no objection to a distinction between Bachelors of Arts in Letters
and Bachelors of Arts in Science. But it is perfectly well understood
that in this community the degree of Bachelor of Arts is for most men
the one essential condition of admission to the noble fraternity of
scholars, to what has been called the "Guild of the Learned." To refuse
this degree to a certain class of our graduates is to exclude them from
such associations and from the privileges which they afford; and this is
just what is intended. Hence I say that the argument is not ingenuous,
and it is not charitable because it implies that a class of men who
profess to love the truth as their lives are seeking to appear under
false colors. To cite examples from my own profession only, I have
always maintained that such men as Davy, Dalton, and Faraday were as
truly learned, as highly cultivated, and as capable of expressing their
thoughts in appropriate language, as the most eminent of their literary
compeers, and I shall continue to maintain this proposition before our
American community, and I have no question that sooner or later my claim
will be allowed, and the doors of the "Guild of the Learned" will be
opened to all scholars who have acquired by cultivation the same power
which these great men held in such a pre-eminent degree by gift of
Nature.

Lastly, I am persuaded that in a large body politic like this it is
unwise, and in the long run futile, to attempt to protect any special
form of culture at the expense of another. If one member suffers, all
the members suffer with it; and what is for the interest of the whole is
in the long run always for the interest of every part. I would welcome
every form of culture which has vindicated its efficiency and its value,
and in so doing I feel that I should best promote the interests of the
special department which I have in charge.




XI.

SCIENTIFIC CULTURE; ITS SPIRIT, ITS AIM, AND ITS METHODS.[P]


I assume that most of those whom I address are teachers, and that you
have been drawn here by a desire to be instructed in the best methods of
teaching physical science. It has therefore seemed to me that I might
render a real service, in this introductory address, by giving the
results of my own experience and reflection on this subject; and my
thoughts have been recently especially directed to this topic by the
discussion in regard to the requisites for admission, which during the
past year have actively engaged the attention of the faculty of this
college.

  [P] An address delivered at the opening of the Summer School of
      Chemistry at Harvard College, July 7, 1884.

At the very outset of this discussion we must be careful to make a clear
distinction between instruction and education--between the acquisition
of knowledge and the cultivation of the faculties of the mind. Our
knowledge should be as broad as possible, but, in the short space of
human life, it is not, as a rule, practicable to cultivate, for
effective usefulness, the intellectual powers in more than one
direction.

Let me illustrate what I mean from that department of knowledge which is
at once the most fundamental and the most essential. I refer to the
study of language. No person can be regarded as thoroughly educated who
has not the power of speaking and writing his mother-tongue accurately,
elegantly, and forcibly; and scholars of the present day must also
command, to a considerable extent, both the French and the German
languages. These three languages, at least, are the necessary tools of
the American scholar, whatever may be the special field of his
scholarship, and his end is gained if he has acquired thorough command
of these tools. But if he goes further, and studies the philology of
these languages, their structure, their derivation, their literature,
the study may occupy a lifetime, and be made the basis of severe
intellectual training. More frequently, and as most scholars think more
effectually, such linguistic training is obtained by the study of the
ancient languages, especially the Latin and the Greek, and no one
questions the value and efficiency of this form of mental discipline.
But obviously such a preparation is not necessary for the use of the
modern languages as tools, or in order to acquire a knowledge of ancient
history, of the modes of ancient life, or the results of ancient
thought. In recent discussions a great deal has been said about the
value of classical learning, and it has been argued that no man could be
regarded as thoroughly educated who had never heard of Homer or Virgil,
of Marathon or Cannæ, of the Acropolis of Athens or the Forum of Rome.
Certainly not. But all this knowledge can be acquired without spending
six years in learning to read the Latin and Greek authors in the
original, or in writing Latin hexameters or Greek iambics. The
discipline acquired by this long study is undoubtedly of the highest
value, but its value depends upon the intellectual training which is the
essential result, and not upon the knowledge of ancient life and
thought, which is merely an incident.

Now, this same distinction, which I have endeavored to illustrate on
familiar ground, must not be forgotten in considering the relations of
physical science to education. Physical science may also be studied from
two wholly different points of view: First, to acquire a knowledge of
facts and principles, which are among the most important factors of
modern life; secondly, as a means of developing and training some of
the most important intellectual faculties of the mind--for example, the
powers of observation, of conception, and of inductive reasoning.

The experimental sciences must often be studied chiefly from the first
point of view. If no man can be regarded as thoroughly educated who is
ignorant of the outlines of Roman and Greek history: one who knows
nothing of the principles of the steam-engine, or of the electric
telegraph, is certainly equally deficient. I do not question that in our
high-schools the physical sciences must be taught, for the most part, as
funds of useful knowledge, and in regard to such teaching I have only a
few remarks to make. Assuming that information is the end to be
attained, the best method of securing the desired result is to present
the facts in such a way as will interest the scholar, and thus secure
the retention of these facts by his memory. I think it a very serious
mistake to attempt to teach such subjects by _memoriter_ recitations
from a text-book, however well prepared. This method at once makes the
subject a task; and, if in addition the preparation for an examination
is the great end in view, it is wonderful how small is the residuum
after the work is done. Such subjects can always be made intensely
interesting if presented by lectures, with the requisite illustrations,
and I do not believe that the cramming process required to pass an
examination adds much to the knowledge previously gained. Many teachers,
finding that the parrot-like learning of a text-book is unprofitable,
attempt to make the exercise more valuable by means of problems--usually
simple arithmetical problems--depending upon principles of physics or
chemistry. And there can be no doubt that such problems do serve to
enforce the principles they illustrate; but I am afraid they also more
frequently, by disgusting the student, stand in the way of the
acquisition of the desired knowledge.

It must not be forgotten, in studying the results of science, that the
facts are never fully learned unless the learner is made to understand
the evidence on which the facts rest. The child who reads in his
physical geography that the world revolves on its axis, learns what to
him is a mere form of words, until he connects this astronomical fact
with his own observation that the sun rises in the east and sets in the
west; and so the scholar who reads that water is composed of oxygen and
hydrogen has acquired no real knowledge until he has seen the evidence
on which this fundamental conclusion rests. Let, then, the sciences be
taught as they have been in schools, as important parts of useful
knowledge, but let them so be taught as to engage the interest of the
scholar, and to direct his attention to the phenomena of Nature.

All this, however, is not scientific culture, in the sense in which I
have constantly used the term, and does not afford any special training
for the intellectual faculties. For myself, I do not desire any study of
natural history, chemistry, or physics from this point of view as a
preparation for college; simply because, with the large apparatus of the
university, all these subjects can be presented more effectively, and be
made more interesting, than is possible in the schools. What I desire to
see accomplished by our schools is a training in physical science,
comparable in extent and efficiency with that which they now accomplish
in the ancient languages. And this brings me to another topic, namely,
scientific culture as a system of mental training.

Before attempting to state in what scientific culture consists, we shall
do well, even at the expense of some repetition, to show that what often
passes for scientific culture is far different from the system of
education which we have so constantly advocated. The acquisition of
scientific knowledge, however extensive, does not in itself constitute
scientific culture, nor is the power of reproducing such knowledge, at a
competitive examination, any test of real scientific power.
Nevertheless, the examination papers which have been published by the
universities of England and of this country show that this is the sole
test of scientific scholarship on which most of these universities rely,
in awarding their highest honors to students in physical science. The
power of so mastering a subject as to be able to reproduce any portion
of it with accuracy, completeness, and elegance, at a written
examination, is the normal result of literary, not of scientific,
culture, and the power is of the same order, whether the subject-matter
be philology, literature, art, or science. Indeed, scientific are, as a
rule, much less adapted than literary subjects to the cultivation of
this power. Moreover, it is also true that scholars, having attained to
a very high degree of scholarship, may not possess this power of stating
clearly and concisely the knowledge they actually possess. We have all
of us known eminent men, possessing in a very high degree the power of
investigating Nature, who have been wholly unable to state clearly the
knowledge they have themselves discovered. Great harm has been done to
the cause of scientific culture by attempting to adapt the well-tried
methods of literary scholarship to scientific subjects: for, as I have
said in another place, competitive examinations are no test of real
attainment in physical science.

Let me not be understood as disparaging the retentive memory and power
of concentration which enable the student to reproduce acquired
information with accuracy, rapidity, and elegance. This is a power of
the very highest order, and is the result of the cultivation to a high
degree of many of the noblest faculties of the mill. And I wish to
enforce is, that success in such examinations is no indication of
scientific culture, properly so called.

What, then, are the tests of true scientific scholarship? The answer can
be made perfectly plain and intelligible. The real test is the power to
study and interpret natural phenomena. As in classical scholarship the
true test of attainment is the power to interpret the delicate shades of
meaning expressed by the classical authors, so in science the true test
is the power to read and interpret Nature; and this last power, like the
other, can as a rule only be acquired by careful and systematic
training. As some men have a remarkable facility for acquiring
languages, so also there are men who seem to be born investigators of
Nature; but by most men such powers can only be acquired through a
careful training and exercise of the faculties of the mind, on which
success depends. No man would be regarded as a classical scholar,
however broad and extended his knowledge, if that knowledge had been
acquired solely by reading English translations of the classical
authors, however excellent. So, no man can be regarded as a scientific
scholar whose knowledge of Nature has been solely derived from books.
In either case the real scholar must have been to the fountain-head and
drawn his knowledge from the original sources. In order, then, to
discover how scientific culture must be gained, we must consider the
conditions on which the successful study and interpretation of Nature
depend.

Of the powers of the mind called into exercise in the investigation of
Nature, the most obvious and fundamental is the power of observation. By
power of observation is not meant simply the ability to see, to hear, to
taste, or to smell with delicacy, but the power of so concentrating the
attention on what we observe as to form a definite and lasting
impression on the mind. There are undoubtedly great differences among
men in the acuteness of their sensations, but successful observation
depends far less upon the acuteness of the senses than on the faculty of
the mind which clearly distinguishes and remembers what is seen and
heard. We say of a man that he walks through the world with his eyes
shut, meaning that, although the objects around him produce their normal
impression on the retina of his eye, he pays no attention to what he
sees. The power of the naturalist to distinguish slight differences of
form or feature in natural objects is simply the result of a habit,
acquired through long experience, of paying attention to what he sees,
and the want of this power in students who have been trained solely by
literary studies is most marked.

An assistant, who was at the time conducting a class in mineralogy, once
said to me: "What am I to do? One of my class can not see the difference
between this piece of blende and this piece of quartz" (showing me two
specimens which bore a certain superficial resemblance in color and
general aspect). My answer was, "Let him look until he can see the
difference." And, after a while, he did see the difference. The
difficulty was not lack of vision, but want of attention.

The power of observation, then, is simply the power of fixing the
attention upon our sensations, and this power of fixing the attention is
the one essential condition of scholarship in all departments of
learning. It is a power which ought to be cultivated at an early age,
and in a system of scientific culture the sciences of mineralogy and
botany afford the best field for its culture, and I should therefore
place them among the earliest studies of a scientific course. Minerals
and plants may be profitably studied in the youngest classes of our
secondary schools, but they should be studied solely from specimens,
which the scholar should examine until he can distinguish all the
characteristics of form, feature, or structure. I am told that in many
of our secondary schools both mineralogy and botany are studied with
great success and interest in the manner I have indicated. But a mistake
is frequently made in attempting to do too much. With mineralogy or
botany as classificatory sciences, our secondary schools should have
nothing to do. The discrimination between many, even of the commonest,
species of minerals or plants depends upon delicate distinctions which
are quite beyond the grasp of young minds, and the study of botany
frequently loses all its value, through the ambition of the teacher to
embrace so much of systematic botany as will enable scholars "to analyze
plants."

If a child, twelve or fourteen years of age, is made to observe the
characteristic qualities of a few common minerals so as to enable it to
recognize them in the rocks, and is likewise led to examine the
structure of a few familiar flowers, not only will a new power have been
acquired, but a new interest will have been added to life.

Of course, the faculty of observation thus early exercised in childhood
only attains the highest degree of development after long experience and
continued practice. The acuteness which practice gives is frequently
very remarkable, and rude men often surprise us by the extent to which
their power of observation has been cultivated in certain special
directions. The sailor who recognizes the outlines of to him a
well-known coast, where the ordinary traveler sees nothing but a bank of
clouds, or the miner who recognizes in the rock indications of valuable
ores, are illustrations which may give a clearer conception of the
nature of the power we have been attempting to describe.

Naturally following the power of observation in the order of education
is the power of conception with the cognate power of abstraction; that
is, the power of forming in the mind distinct and accurate images of
objects, and relations, which have been previously apprehended either by
direct observation, or through description; and also the power of
confining the attention to certain features which these images may
present to the exclusion of all others. This is a power which depends
very greatly on the imagination and is capable of being cultivated to a
very high degree. There is no study which is so well suited to the
training both of the powers of conception and of abstraction as the
study of geometry.

To this end the study of geometry should be begun at an early period in
school-life, and it should be studied at first not as a series of
propositions logically connected, but as a description of the properties
and relations of lines, surfaces, and solids--what has sometimes been
called "the science of form." A text-book prepared on this idea by Mr.
G. A. Hill forms an admirable introduction to the study.

I esteem very highly the system of geometry of Euclid, either in its
original form or as it has been modified by modern writers, as a means
of developing the logical faculty. The completeness of the proof of the
successive propositions and their mutual dependence by means of which,
as on a series of steps, we mount from simple axiomatic truths to the
most complex relations, furnish an admirable discipline for the
reasoning power; but too often the whole value of this discipline is
lost by the failure of the pupil to form a clear conception of the very
relations about which he is reasoning, and the study becomes an exercise
of the memory and nothing more. Often have I seen a conscientious and
faithful student draw an excellent figure, and write out an accurate
demonstration, without noticing that the two were not mated; and in a
recent meeting of teachers of our best secondary schools it was gravely
asserted that solid geometry is the most difficult study with which the
teachers had to deal. In solid geometry, however, the reasoning is no
more difficult than in plane geometry, but the conceptions are far more
complex, and, if the teacher insisted that the pupil should not take a
single step until his conceptions were perfectly clear, all the
difficulties would disappear. Of this I am fully persuaded, for I have
had to encounter the same difficulties over and over again in teaching
crystallography. In beginning the study of geometry, of course the power
of conception should be helped in every possible way. Let your pupil
find out by actual measurement that the sum of the angles of a triangle
is equal to two right angles, and he will easily discover the proof of
the proposition himself. So, also, if he actually divides with his knife
a triangular prism made from a potato or an apple into three triangular
pyramids, he will find no difficulty in following the reasoning on which
the measurement of the solid contents of a sphere depends. Let me assure
teachers that the study of geometry, taught as I have indicated, is a
most valuable introduction to the study of science. But, as it has been
usually taught as a preparation for college, it is almost worthless in
this respect, however valuable it may be as a logical training.

I consider practice in free-hand drawing from natural objects a most
valuable means of training both the power of observation and the power
of conception, besides giving a skill in delineation which is of the
greatest importance to the scientific student. Accuracy of drawing
requires accuracy in observation, and also the ability to seize upon
those features of the object which are the most prominent and
characteristic. Hence, in a course of scientific training, the
importance of practice in drawing can hardly be exaggerated, and it
should be made one of the most important objects of school-work from an
early period.

To the scientific student the powers of observation and conception are
not sought as ends in themselves, but as means of studying Nature. The
precise portions of this wide field to which the attention of the
student shall be directed will be determined by many circumstances, and
it is not our purpose in this address to lay down a plan of study. To
most students the natural history subjects offer the most attractive
field; but all, I think, will admit that the experimental sciences
should form a considerable portion, at least, of the course of all
scientific students, whatever specialty may subsequently be chosen. That
on which I desire particularly to dwell is the spirit in which all these
studies should be pursued; and I can best illustrate what I mean by
confining my remarks to that subject in which I am most interested, and
in regard to which I have the greatest experience.

In a course of scientific study, chemistry can not be dissociated from
physics, and the two sciences ought to be studied to a great extent in
connection with each other. Not only does the philosophy of chemistry
rest upon physical conceptions; but, moreover, chemical methods involve
physical principles. There is, however, a distinction to be made; for,
while some of the departments of physics are best studied as a
preparation for chemistry, there are other subjects which are best
deferred until the student has some knowledge of chemical facts. Among
the preliminary subjects we should mention elementary mechanics,
including hydrostatics and pneumatics, and also thermotics; while
electricity, acoustics, and optics, including the large subject of
radiant energy, may well be deferred until after the study of chemistry.

In the study both of chemistry and physics there are of course two
definite objects to be kept in view: In the first place, a knowledge of
the facts of the science is to be acquired; in the second place, the
student must learn by experience how these facts have been discovered.
It would be obvious, from a moment's reflection, that a knowledge of the
circumstances under which the facts of Nature are revealed to the
student is essential to a complete apprehension of the facts themselves.
The child who is taught that the earth moves in an elliptical orbit
around the sun in one year does not in the least grasp the wonderful
fact thus stated, and will not come to realize it until he connects the
statement with the nightly procession of the stars in the heavens. And
it is just such a connection as this which the teacher must seek to
establish in all scientific teaching. In experimental science such a
connection is most readily established in the mind of the student by
means of a series of well-arranged experiments, which each one repeats
for himself at the laboratory table. Obviously, however, it is
impossible, in a limited course of teaching, to go over the whole ground
of chemistry and physics in this way, or even over that small portion of
the ground with which the average scientific student can expect to
become acquainted. Nor is this necessary; for, after one has realized
the connection between phenomena and conclusion in a number of
instances, the mind will fully comprehend that a similar connection
exists in other cases, and will understand the limitations with which
scientific conclusions are to be received.

Hence, it seems to me that, in teaching chemistry or physics, it is best
to combine a course of lectures which should give a broad view of the
whole ground with a course of laboratory instruction, which must
necessarily be more or less restricted. Experimental lectures are, I am
convinced, much the best way of presenting these subjects as systematic
portions of knowledge. It is not necessary that the lectures should be
formal, but it is all-important that they should be given in such a way
that the interest of the student should be awakened, and that they
should be fully illustrated by specimens and experiments. What we read
in a book does not make one half the impression that is produced by the
words of a living teacher, nor can we realize the facts unless we see
the phenomena described. There is undoubtedly an advantage to be gained
in subsequently reviewing the subject as presented in a good text-book,
and such a book may be of great use in preparation for an examination.
But how far examinations are of value in enforcing the acquisition of
knowledge of an experimental science is a question on which I feel a
grave doubt. Certainly their value is very small if, as is too
frequently the case, they lead the student to defer all effort to make
his own the knowledge presented in the lectures, until a final cram.

The management of lectures, text-books, and examinations, will not,
however, offer nearly so great difficulties to the teacher as the
management of the parallel experimental course of laboratory teaching.
In the last the methods are less well tried and demand of the teacher a
very considerable amount of invention and experimental skill. To follow
mechanically any text-book would result in a loss of the proper spirit
with which the course should be conducted and which constitutes its
chief value. No experiments are so good as those which have been devised
by the teacher, or, still better, by the pupils themselves. A mere
repetition of a process, according to a definite description, has no
more value than a repetition of a form of words in an ordinary school
recitation. The teacher must make sure that the student fully
understands what he is about, and comprehends all the connections
between observations and conclusions which it is his aim to establish.
Moreover, he must constantly encourage his students to think and work
for themselves, and direct them in the methods of inductive reasoning.
The failure of an experiment may be made most instructive if the student
is led to discover the cause of the failure. A leak in his apparatus may
be turned to a similar profit if the student is shown how to discover
the leak, by carefully eliminating one part after another until the weak
point is made evident.

The direction of an experimental laboratory is no easy task. The teacher
must make each man's work his own, and follow his processes of thought
as well as his experiments with the most careful attention. With large
classes much time can be saved by going through each process on the
lecture-room table and giving the directions to the class as a whole;
but this does not supersede the personal attention and instruction which
each student requires at the laboratory table. Moreover, in laboratory
teaching the teacher must rely, as we have said, on his own resources,
and but few aids can be given. There are books, however, which will help
the teacher to prepare himself for his work, and I am happy to say that
a book entitled "The New Physics," prepared by my colleague, Professor
Trowbridge, is now being printed, which I hope will greatly promote the
laboratory teaching of physics. Nichols's abridgment of Eliot and
Storer's Manual has long served a similar valuable purpose in chemistry,
and there are many excellent works on "Qualitative Analysis," a study
which is admirably adapted to develop the power of inductive reasoning.

There is, however, a danger with all laboratory manuals, which must be
sedulously avoided, and the danger is generally greater the more precise
the descriptions. They are apt to induce mechanical habits which are
fatal to the true spirit of laboratory teaching. Not long ago I asked a
student, who was working in our elementary laboratory, what he was
doing. He answered that he was doing No. 24, and immediately went to
find his book to see what No. 24 was. I fear that a great deal of
laboratory work is done in a way which this anecdote illustrates, and,
if so, it is a mere waste of time.

When teaching qualitative analysis it was always with me a constant
struggle to prevent just such a result, and many of the excellent tables
which have been prepared to facilitate analysis simply encourage the
evil practice. It is an error to which college students, with their
exclusively literary preparation, are especially liable, and I have no
question that the proper conduct of our laboratories would be made much
easier if the students came with a previous scientific training.

Thus far I have dealt solely with generalities, and my object has been
not so much to give definite directions as to make suggestions which
might lead to better systems of teaching. The details of these systems
may vary widely, and yet all may lead to the desired result if only the
true spirit of scientific teaching is preserved, and a teacher's own
system is generally the best system for him. This leads me to explain my
own system of teaching chemistry--which presents some novelties that may
be of interest, and, although it has been worked out in detail in the
revised edition of the "New Chemistry," just published, still a few
words of explanation may be of value at this time in setting forth its
salient points.

Chemistry has been usually defined as the science which treats of the
composition of bodies, and in most text-books the aim has been to
develop the scheme of the chemical elements, and to show that, by
combining these elements, all natural and artificial substances may be
prepared. In the larger text-books, which aim to cover the whole ground
and to describe all known substances, such a method is both natural and
necessary. But, as an educational system, this mode of presenting the
subject is, as a rule, profitless and uninteresting. The student becomes
lost amid details which he can only very imperfectly grasp, and the
great principles of the science, as well as their relations to cognate
departments of knowledge, are lost sight of. Moreover, the system is
unphilosophical, because it presents the conclusions of chemistry before
the observations on which they are based. Any one who has attempted to
teach chemistry from the ordinary elementary text-books must have
experienced the truth of what I have said.

A student learns a lesson about sodium and the various salts of this
metal, and, after glibly reciting the words of the text-book, how much
more does he know of the real relations of these bodies than he did
before? Thus: "Chloride of sodium, symbol NaCl. Crystallizes in cubes.
Soluble in water. Solubility only slightly increased by heat. Generally
obtained by evaporation of sea-water in pans. Also found in beds in
certain geological basins, from which it is extracted by mining. When
acted upon by sulphuric acid, hydrochloric acid is evolved and sodic
sulphate is formed, according to the following reaction," and so on. I
have known a student to recite all this and a great deal more, without
ever dreaming that he had been eating chloride of sodium on his food,
three times a day at least, since he was born.

Now, the rational system of teaching chemistry is first to present to
the scholar's mind the phenomena of Nature with which the science deals.
Lead him to observe these phenomena for himself; then show him how the
conclusions which together constitute that system of knowledge we call
chemistry have been deduced from these fundamental facts. My plan is to
develop this system in the lecture-room in as much detail as the time
allotted will permit; to illustrate all the points by experiment, and in
addition to explain more in detail carefully selected fundamental
experiments, which the student subsequently repeats in the laboratory
himself. Thus I make the lecture-room instruction and the laboratory
demonstration go hand in hand as complementary parts of a single course
of teaching.

I begin by directing the student to observe for himself the properties
of bodies by which substances are distinguished. I place in his hands a
bit of roll-brimstone. He first notices the color, the hardness, the
brittleness, and the electrical excitability of this material. He next
determines its density, its melting-point, its point of ignition, and,
if practicable, its boiling-point. Then he treats the brimstone with
various solvents, and finds that, while insoluble in water or alcohol,
it dissolves readily in sulphide of carbon. Afterward he evaporates the
solution thus made, and obtains definite crystals, whose forms he
studies, and compares with the forms of the crystals of the same
material which he also makes by fusion. Lastly, he observes the
remarkable change which follows when fused brimstone is heated above its
melting-point, and also the peculiar plastic condition which the
material assumes when the thickened mass is poured into water. He will
thus be led to see that the same material may assume different states,
and gain a clear conception of the substance we call sulphur. After this
I give the student pieces of two metals which externally resemble each
other, like lead and tin, in order that, after making another series of
observations and experiments, he may come to understand on what
comparatively slight differences of properties the distinction between
substances is frequently based. A comparison is next made of the
properties of two closely-allied liquids, like methylic and ethylic
alcohol; and by this time the student attains sufficient skill in
experimenting to make a comparison between two aëriform substances, like
oxygen gas and carbonic dioxide.

After more or less of such preliminary work, we are prepared to take up
the subject-matter of chemistry. In the broad fields of Nature what
portion does this science cover? Natural phenomena may obviously be
divided into two great classes: First, those changes which do not
involve a transformation of substance; and, secondly, those changes
whose very essence consists in the change of one or more substances into
other substances having distinctive properties. The science of physics
deals with the phenomena of the first class; the science of chemistry
with those of the last. Any phenomenon of Nature which involves a change
of substance is a chemical change, and in every chemical change one or
more substances, called the factors, are converted into another
substance or into other substances called the products. The first point
to be made in teaching chemistry is, that a student should realize this
statement, and a number of experiments should be shown in the
lecture-room and repeated in the laboratory illustrating what is meant
by a chemical change.

Here, of course, arises a difficulty in finding examples which shall be
at once simple and conclusive, for in almost all natural phenomena there
is a certain indefiniteness which obscures the simple process. The
familiar phenomena of combustion are most striking examples of this
fact, and men were not able to penetrate the mist which obscured them
until within a hundred years. To find chemical processes whose whole
course is obvious to an unpracticed observer, we are obliged to resort
to unfamiliar phenomena.

A very simple example of a chemical process is a mixture of sulphur and
zinc in atomic proportions, which, when lighted with a match, is rapidly
converted into white sulphide of zinc, with appearance of flame. Another
example, a mixture of sulphur and fine iron-filings, which, when
moistened with a little water, rapidly changes into a black sulphide of
iron. Then some copper-filings, which, when heated on a saucer in the
open air, slowly change into black oxide of copper. Then a bit of
phosphorus, burned in dry air under a glass bell, yielding a white
oxide. Next, some zinc, dissolved in diluted sulphuric acid, yielding
hydrogen gas and sulphate of zinc. Then, a solution of chloride of
barium added to a solution of sulphate of soda, giving a precipitate of
sulphate of baryta, and leaving in solution common salt, which can be
recovered by evaporating the filtrate.

In all these examples the student should be made to see and handle all
the factors and all the products of each process, and the experiments
should be selected so that he may become familiar with the different
conditions under which substances appear, and with various kinds of
chemical processes. He should also be made clearly to distinguish
between the essential features of the process and the different
accessories, which may be more or less accidental--such, for example, as
the water used in determining the combination of iron and sulphur, or
the flame which accompanies combustion.

After a clear conception has been gained of a chemical process, with its
definite factors and definite products, we are prepared for the next
important step. Every chemical process obeys three fundamental laws:

  The Law of Conservation of Mass.
  The Law of Definite Proportions.
  The Law of Definite Volumes.

According to the first law, the sum of the weights of the products of a
chemical process is always equal to the sum of the weights of the
factors. This law must now be illustrated by experiments, and
approximate quantitative determinations should be introduced thus early
into the course of study. All that is required for this purpose is a
common pair of scales, capable of weighing two or three hundred grammes,
and turning with a decigramme. We use in our laboratory some
platform-scales, made by the Fairbanks Company, which are inexpensive,
and serve a very useful purpose.

A very satisfactory illustration of the law of conservation of mass can
be obtained by inserting in a glass flask a mixture of copper-filings
and sulphur in atomic proportions. The glass flask is first balanced in
the scale-pan; then removed and gently heated until the ignition which
spreads through the mass shows that chemical combination has taken
place. The flask is lastly allowed to cool, and on reweighing is found
not to have altered in weight.

For a second experiment, a bit of phosphorus may, with the aid of some
simple contrivance, be burned inside a tightly-corked glass flask, of
sufficient volume to afford the requisite supply of oxygen. Of course,
on reweighing the flask, after the chemical change has taken place, and
the bottom of the flask covered with the white oxide formed, there will
be no change of weight, and this experiment may be made to enforce the
truth that, in this example of combustion at least, the chemical process
is attended with no loss of material. Open now the flask, and air will
rush in to supply the partial vacuum, proving that in the process of
combustion a portion of the material of the air has united to form the
white product.

Make now a third experiment as an application of the general principle
which has been illustrated by the previous experiments. Burn some finely
divided iron (iron reduced by hydrogen) on a scale-pan, and show that
the process is attended by an increase of weight. What does this mean?
Why, that some material has united with the iron to form the new
product. Whence has this material come? Obviously from the air, for it
could come from nowhere else. And thus, besides illustrating the first
of the above laws, this experiment may be made to furnish an instructive
lesson in regard to the relations of the oxygen of the atmosphere to
chemical processes.

The second law declares that in every chemical process the weights of
the several factors and products bear each to the others a definite
proportion. This law must next be made familiar by experimental
illustrations. A weighed amount of oxide of silver is placed in a glass
tube connected with a pneumatic trough. The tube is gently heated until
the oxide is decomposed and the oxygen gas collected in a glass bottle
of sufficient size. The metallic silver remaining in the tube is now
reweighed, and the volume of the oxygen gas in the bottle measured, and
from the volume of the gas its weight is deduced. The measurement is
easily made by simply marking with a gummed label the level at which the
water stands in the bottle. If, now, the bottle is removed from the
pneumatic trough and the weight of water found which fills the bottle to
the same height, the weight of the water in grammes will give the volume
of the gas in cubic centimetres, and, knowing the weight of a cubic
centimetre of oxygen, we easily calculate the weight of this gas
resulting from the chemical process. We have now the weights of the
oxide of silver, the silver, and the oxygen, the one factor and the two
products of the chemical process, and, by comparing the results of
different students making the same experiment, the constancy of the
proportion will be made evident to the class.

For a second illustration of the same law, the solution of zinc in
dilute sulphuric acid, yielding sulphate of zinc and hydrogen gas, may
be selected, and the weight of the hydrogen, estimated as in the
previous example, shown to sustain a definite relation to the weight of
the zinc dissolved.

Again, silver may be dissolved in nitric acid, and the weight of the
nitrate of silver obtained shown to sustain a definite relation to the
weight of the metal.

Or, still further, as an experiment of a wholly different class, a known
weight of chloride of barium may be dissolved in water, and, after
precipitation with sulphuric acid, the baric sulphate collected by
filtration and weighed, when the definite relation between the weight of
the precipitate and the weight of the chloride of barium will appear.

For a last experiment let the student neutralize a weighed amount of
dilute hydrochloric acid with aqua ammonia, noting approximately the
amount of ammonia required. Let him now evaporate the solution on a
water-bath, and weigh the resulting saline product; taking next the same
quantity of hydrochloric acid as before, and, having added twice the
previous quantity of ammonia, let him obtain and weigh the resulting
salammoniac as before. A third time let him begin with half the
quantity of hydrochloric acid, and, adding as much ammonia as in the
first case, again repeat the process. It is obvious what the result of
these experiments must be; but without telling the student what he is to
expect, it will be a good exercise to ask him to draw his own inferences
from the results. Of course, he must previously have so far been made
acquainted with the properties of hydrochloric acid and ammonia as to
know that the excess of either would escape when the saline solution is
evaporated over a water-bath. But with this limited knowledge he will be
able to deduce the law of definite proportions from the experimental
results thus simply obtained.

The third of the fundamental laws of chemistry stated above (generally
known as the law of Gay-Lussac) declares that, when two or more of the
factors or products of a chemical process are aëriform, the volumes of
these gaseous substances bear to each other a very simple ratio. Here,
again, numerous experiments may be contrived to illustrate the law.
Water, when decomposed by electricity, yields hydrogen and oxygen gases
whose volumes bear to each other the ratio of two to one. When
hydrochloric-acid gas is decomposed by sodium amalgam, the volume of the
original gas bears to that of the residual hydrogen the ratio also of
two to one. When ammonia is decomposed by chlorine, the volume of the
resulting nitrogen gas is one third of that of the chlorine gas
employed.

Having illustrated these three general laws, attention should be
directed to the fact that the nature of a chemical process and the laws
which it obeys are results of observation and involve no theory
whatsoever. On these facts the science of chemistry is built. The modern
system of chemistry, however, assumes what is known as the molecular
theory, and by means of this theory attempts to explain all these facts
and show their mutual relations. Here the distinction between fact and
theory must be insisted upon, and also the value of theory for
classifying facts and directing observation.

A molecule is now defined, and, if the student has not studied physics
sufficiently to become acquainted with the outlines of the kinetic
theory of gases, this theory must be developed sufficiently to give the
student a knowledge of the three great laws of Mariotte, of Charles, and
of Avogadro. He must be made to understand how molecules are defined by
the physicist, and how their relative weights may be inferred by a
comparison of vapor densities. He should then be made to compare the
relative molecular weights, deduced by physical means, with the definite
proportions he has observed in chemical processes. He will thus himself
be led to the conclusion that these definite proportions are the
proportions of the molecular weights, and that the constancy of the law
arises from the fact that in every chemical process the action takes
place between molecules, and that the products of the process are new
molecules, preserving always, of course, their definite relative
weights. The student will thus be brought to the chemical conception of
the molecule as the smallest mass of any substance in which the
qualities inhere, and he will come to regard a chemical process as
always taking place between molecules.

Thus far nothing has been said about the composition of matter. A
chemical process has been defined simply as certain factors yielding
certain products, but nothing has been determined about the relations of
these several substances except in so far as they are defined by the
three laws illustrated above. But now it must be shown that a study of
different chemical processes compels us to conclude that in some cases
two or more substances unite to form a compound, while in other cases a
compound is broken up into simpler parts. Thus, when copper-filings are
heated in the air, it is evident that the material of the copper has
united with that portion of the air we call oxygen to form the black
product we call oxide of copper; and again, when oxide of silver is
heated, it is evident that the resulting silver and oxygen gas were
formerly portions of the material of the oxide. So, when water is
decomposed by electricity, the conditions of the experiment show that
the resulting oxygen and hydrogen gases must have come from the material
of the water, and could have come from nothing else.

Experiments should now be multiplied until the student has a perfectly
clear idea of the nature of the evidence on which our knowledge of the
composition of bodies depends. The decomposition of chlorate of potash
by heat, yielding chloride of potassium and oxygen gas; the
decomposition of nitrate of ammonium by heat, yielding nitrous oxide and
water; the decomposition of this resulting nitrous oxide, when the gas
is passed over heated metallic copper; and, lastly, the decomposition
already referred to, of water by electricity--are all striking
experiments by which the evidence of chemical composition may be
enforced.

The distinction between elementary and compound substances having been
clearly defined by the course of reasoning already given in outline, the
next aim should be to lead the student to comprehend how substances are
analyzed and their composition expressed in percents. The reduction of
oxide of copper by hydrogen gives readily the data for determining the
composition of water, which is thus shown to contain in one hundred
parts 11·11 per cent of hydrogen and 88·89 per cent of oxygen.

Another substance whose analysis can be very readily made by the student
is carbonate of magnesia. By igniting pure carbonate of magnesia in a
crucible (not of course the "magnesia alba" of the shops), the
proportions of carbonic acid and magnesia can be readily determined.
Then, by burning magnesium ribbon, and weighing the product, the student
easily finds the relative weight of magnesium and oxygen in the oxide.
And, lastly, the proportion of carbon and oxygen in carbonic dioxide is
easily deduced from the burning of a weighed amount of carbon. Here the
result may be expressed either in percents of oxide or magnesium and
carbonic dioxide, or else in percents of the elementary substances,
carbon, magnesium, and oxygen.

After making a few analyses like these, the student will be prepared to
comprehend the actual position of the science. All known substances have
been analyzed, and the results tabulated, so that it is unnecessary to
repeat the work except in special cases.

The teacher is now prepared to take a very important step in the
development of the subject. If the molecule is simply a small particle
of a substance in which the qualities of the substance inhere, then it
follows, of course, that the composition of the molecule is the same as
the composition of the substance. The percentage results of the analysis
of water, or of carbonate of magnesia, indicate the composition of a
molecule of water or a molecule of carbonate of magnesia. Thus, 11·11
per cent of every molecule of water consists of hydrogen, while 88·89
per cent consists of oxygen. Hence it follows that, in a chemical
process, the molecules must be divided, and these elementary parts of
molecules which analysis reveals are the atoms of chemistry. Moreover,
as we know the weights of molecules, both by physical and chemical
means, chemical analysis now gives us the weights of the atoms. We have
no time to dwell on the details of this reasoning, but the general
course to be followed will be evident, and it must be enforced by
numerous examples.

Assuming that the student fully comprehends the distinction between
molecules and atoms--that is, between the physically smallest particles
and the chemically smallest particles--he is prepared to master the
symbolical nomenclature of chemistry, with a very few words of
explanation. The initial letters of the Latin names are selected to
represent the atoms of the seventy known elementary substances, and
these letters stand for the definite atomic weights which are tabulated
in all chemical text-books. The symbols of the atoms are simply grouped
together to form the symbols of the molecules of the various
substances; the number of atoms of each kind entering into the
composition of the molecule being indicated by a subscript numeral.
Lastly, in order to represent chemical processes, the symbols of the
molecules of the factors are written on one side and the symbols of the
molecules of the products are written on the other side of an equation,
the number of molecules of each substance involved being indicated by
numerical coefficients.

The atomic symbols, as we have seen, stand for definite weights. In the
same way, the molecular symbols stand for definite weights, which are
the sums of the weights of the atoms of which each consists, and in
every chemical equation the weights of the molecules represented on one
side must necessarily equal the weights of the molecules represented on
the other. The chemical process consists merely in the breaking up of
certain molecules, and the rearrangement of the same constituent atoms
to form new molecules. Again, as the molecular symbols represent
definite weights, the equation also indicates that a definite proportion
by weight is preserved between the several factors and products of the
process represented.

Again, since every molecular symbol represents the same volume when the
substance is in an aëriform condition, it follows that the relative gas
volumes are proportional to the number of molecules of the aëriform
substances involved in the reaction. Thus it is that these chemical
equations or reactions are a constant declaration of the three great
fundamental laws of chemistry.

In order to enforce the above principles, a great number of examples
should now be given which should be so selected as to illustrate
familiar and important chemical processes, including the all-important
phenomena of combustion. In each case, the student, having made the
experiment, should write the equation or reaction which represents the
process, and should be made to solve a sufficient number of
stochio-metrical problems, involving both weights and volumes, to give
him a complete mastery of the subject. Such questions as these will test
the completeness of his knowledge:

Why is the symbol of water H_{2}O? What information does the symbol
CO_{2} give in regard to carbonic-dioxide gas? Write the reaction of
hydrochloric acid on sodic carbonate, and state what information the
equation gives in regard to the process which it represents.

Of course, such questions may be greatly multiplied, and I cite these
three only to call attention to the features of the method of
instruction I have been endeavoring to illustrate.

But, besides teaching the general principles of chemical science, it is
important to give the student a more or less extended knowledge of
chemical facts and processes--especially such as play an important part
in daily life, or in the arts--and such knowledge can readily be given
in this connection. Beyond this I do not deem it desirable to go in an
elementary course of instruction. The way, however, is now opened to the
most advanced fields of the science. A comparison of symbols and
reactions leads at once to the doctrine of quantivalence, and to the
results of modern structural chemistry which this doctrine involves.
Among these results there is of course much that is fanciful, but there
is also a very large substratum of established truth; and if the student
thoroughly comprehends the symbolical language of chemistry, and
understands the facts it actually represents, he will be able to
realize, so far as is now possible, the truths which underlie the
conventional forms.

The study of the structure of molecules naturally leads to the study of
their stability, and of the conditions which determine chemical changes,
and thus opens the recently explored field of thermo-chemistry. To be
able to predict the order and results of possible conditions of
association of materials, or of chemical changes under all
circumstances, is now the highest aim of our science, and we have
already made very considerable progress toward this end.

But I have detained you too long, and I must refer to the "New
Chemistry" for a fuller exposition of this subject. My object has been
gained if I have been able to make clear to you that it is possible to
present the science of chemistry as a systematic body of truths
independent of the mass of details with which the science is usually
encumbered, and make the study a most valuable means of training the
power of inductive reasoning, and thus securing the great end of
scientific culture.




XII.

"NOBLESSE OBLIGE."


In the former essays of this volume I have earnestly maintained that
scientific culture, rightly understood, is a suitable basis for a
liberal education; and I have maintained this thesis without in any way
attempting to disparage that literary culture hitherto so generally
regarded as the only basis on which the liberal arts could be built.
While, however, I have argued that, in the present condition of the
world, there is more than one basis of true scholarship, I have fully
admitted that for far the larger number of scholars, including all those
whose lives are to be occupied with literary pursuits, the old system of
education is still the best. Moreover, I have endeavored to point out
that scientific culture in no way conflicts with literary culture; that
it has a different spirit, a different method, and a different aim; and
I have only recommended it as suitable to those who are distinctly
preparing themselves for a scientific calling; but I have maintained
that for such men scientific studies, rightly followed, may lead to a
broad, a noble, and in the truest sense a liberal education.

I have used the term scientific culture _rightly understood_ in order to
mark a distinction; because a great deal that passes for scientific
scholarship in the world does not imply true scientific culture. In all
departments of learning, and not less in scientific than in literary
studies, erudition does not necessarily imply a high degree of culture.
We all value the labors of the lexicographer, and the work may be so
done as to task the noblest intellectual power; but there is a higher
form of literary culture than that which dictionary-making usually
implies. So also in science, no amount of book-learning constitutes what
we have called scientific culture rightly understood. For example, the
ability to pass an examination on the facts and principles of science is
no test whatever of the form of culture we are advocating. Not that we
underrate the value of such tests, or of the knowledge they imply; but
the ability to master a subject as presented in a text-book, and to
state that knowledge in a concise and accurate form, is the normal
result of literary, not of scientific culture. The power to do
something well is involved in the very idea of culture, and the scholar
who can pass a successful written examination has acquired a power which
literary culture chiefly gives, and that this power may be applied to
scientific as well as literary subjects is obvious. Here is a most
important distinction in connection with our subject. Culture implies
the acquisition of some power of the mind in an eminent degree, and such
power is constantly associated with erudition, simply because it leads
to erudition. But when we see erudition without such power, as we often
do in every department of scholarship, we perceive at once upon how much
lower a level it stands. What very different things are classical
scholarship and classical erudition; and is not the power which the
great classical scholars possess of interpreting the thoughts of the
classical authors, and of reproducing their life, the great element of
difference between the two?

So scientific culture implies the ability to interpret Nature, to
observe her phenomena, and to investigate her laws. The scholar, to whom
Nature presents merely an orderly succession of facts and phenomena,
knows nothing of true scientific culture. As there is a spirit in the
great writers of classical antiquity which ennobles the study of the
forms in which the thoughts of these authors were expressed, so also is
there a spirit in Nature without which facts and phenomena, however well
classified, create no intellectual elevation. The last century of the
world's history has been marked, more than by anything else, by the
increase of our knowledge of Nature, and it will be known in history as
the age of great discoveries; but valuable as the facts and principles
of science certainly are, greatly as they have promoted the well-being
of mankind, and important, therefore, as the knowledge of these facts
and principles must be to man, yet nevertheless I should never urge the
claims of physical science as a basis of liberal education if they could
be defended on no other grounds than these. It is here as elsewhere "the
spirit which giveth life"; and the power to interpret Nature, and to
commune with the intelligence that rules the universe, is the one
acquisition which, above all others, gives worth and dignity to the form
of culture we have endeavored to advocate in these essays.

Those who regard science simply as utilitarianism, and who value
scientific studies solely because they teach men how to build railroads,
to explore mines, to extract the useful metals from their ores, or to
increase the yield of agriculture, have an even more imperfect
conception of what is meant by scientific culture than those to whom
science is merely a valuable erudition. It is true that physics and
chemistry may be studied as arts rather than as sciences, and we have no
desire to underrate the importance of such technical education; but the
difference between the two modes of study is as wide as the difference
between the artisan and the scholar. In asserting this we do not forget
that the occupations of the engineer, the electrician, and the
analytical chemist demand a very large amount of knowledge, judgment,
and skill, and are rightly regarded as learned professions. But let it
not be supposed that skill in such professions is the end or aim of
scientific culture; any more than legal skill is the end or aim of
literary culture. If literary scholars regard the study of science
solely from this point of view, it is no wonder that they think that the
tone of scholarship would be lowered if it rested solely on such a
utilitarian basis; and, on the other hand, if they could once realize
the sublimity of Nature, as Copernicus, Newton, Faraday, and unnumbered
others have realized it, this fear that devotion to science must degrade
scholarship would disappear.

We are well aware that practical men frequently regard with undisguised
contempt the students of theoretical science, and that the greater
number of persons seeking a scientific education must look for
employment to the practical professions in which this tone too often
prevails. But, certainly, a narrow technical spirit prevails quite as
often in the professions in which literary scholars chiefly find
employment; and the new scientific professions are even more closely
dependent on the discussion of theoretical and abstract principles than
those which have hitherto been exclusively regarded as liberal. It is an
admitted fact, as we have shown in another place, that all the great
advances in practical science, all the great inventions, which during
the last century have so wonderfully increased the power of man over
Nature, may be traced directly to the results of theoretical study. For
this reason, if on no higher ground, we have claimed that it is both the
interest and the duty of the State to foster and reward scientific
investigation. The time is not far distant, if it is not already at
hand, when the scientific culture of a people will be one of the chief
factors in determining its position among the nations of the world.

We can not leave this subject without giving prominence to another
thought, which has been ever present with us while writing these pages,
if not hitherto distinctly stated. Culture, as we have seen, implies
power, and the possession of power also involves corresponding
obligations. Among the many blessings which Christianity and its
attendant civilization have brought to mankind, the recognition of this
principle is most plainly marked. The principle is assumed in almost
every relation of life, even when not distinctly acknowledged; and
happily it can rarely now be disregarded without incurring the odium of
mankind. It leads the possessors of great wealth to devote no
inconsiderable share of their fortunes to the public good; it
stigmatizes as miserly any neglect of this obligation; and the best hope
of preserving our modern civilization against the destructive agencies
of socialism is to be found in the increasing recognition and
enforcement of this saving grace.

But while this principle is, to a greater or less degree, acted upon in
all relations of life, it is enforced by public opinion with special
strictness upon those who assume to be the servants of the people. In
political life the obligations it imposes are already very generally
recognized; and still more strongly are they felt by the ministers of
religion. The politician who uses his high position to promote his
personal interests may sometimes escape his just deserts; but the
clergyman who prostitutes his influence for private gains is universally
condemned. So true is this, that a clergyman is debarred by his
profession from many of the industries and occupations of life which are
regarded as perfectly honorable callings for other men. A clergyman who
speculated in stocks, or even engaged in a mercantile pursuit, would,
with good reason, lose the respect of the very men who had gained their
wealth by the same ways which they deny to him. He may not, like the
members of the elder religious fraternities, take the vow of poverty,
but still he is held to a very strict rule of life; and on this is based
his claim to an adequate support from the people to whom he ministers.
Because "appointed to sow spiritual things," the clergy are entitled "to
reap worldly things" which they have not sown nor gathered; and evil
will be the days when this claim is disallowed.

Now, we hold that the profession of a scientific teacher implies an
obligation not less binding than that which rests on the clergyman; and
this is especially true if the teacher has been placed in a conspicuous
and responsible position before the world. The teacher has been set
apart as truly as the clergyman, and, if he uses the influence of his
office merely as a means of accumulating wealth, he is not loyal to the
profession which he has voluntarily assumed. Let me not be
misunderstood. There are a thousand legitimate ways of earning a
livelihood and acquiring wealth by means of the knowledge which
scientific study gives; and a man has a right to use scientific
knowledge for his worldly advancement as freely as any other knowledge.
But the man who has accepted the post of a teacher, and receives the
support to which his position entitles him, is bound to do the work of a
teacher to the best of his ability, and to devote his whole energies to
extending the knowledge of the science which he professes to teach. It
is of the utmost importance that the community should be educated up to
this point, and should hold its teachers to their trusts and obligations
as strictly as it does its clergy. Indeed, the scientific even more than
the religious teacher requires the aid of a correct public sentiment to
maintain the tone of his profession. Scientific knowledge and acumen,
when centered on business relations, has often discovered direct avenues
to wealth; the temptation to make use of the opportunities thus offered
is of course very great, and in most of the relations of life the career
so opened may be perfectly legitimate and honorable. But no one can
expect to succeed in any business career without devoting his whole
energy to the work, and there are conditions under which such a course
would involve the betrayal of a trust. Nor are the words betrayal of a
trust too strong; for it is sometimes the case that, besides neglecting
his appropriate work, the scientific teacher sells the reputation of his
position, and commands a higher price because he barters the good name
of the institution with which he is connected.

I am well aware that there is another side to this question. In many of
our colleges the professor has an inadequate support, and is expected or
even invited to supplement his income by what is technically called
"commercial work." Of course, in such cases the man can not be blamed;
but public opinion should be such as to prevent a respectable
institution from offering, or a respectable professor from accepting,
such a position. The workman is worthy of his hire, and the same
sentiment which demands from the scientific professor a whole-hearted
devotion to his work, demands also from the community for which he works
an adequate support.

It is undoubtedly in consequence of the inadequate support which
scientific teachers generally receive in this country that public
sentiment tolerates with them practices which sober judgment must
condemn; and it must be remembered that under these circumstances a
teacher, if he is faithful to the routine of his office, may devote his
remaining energies to commercial work, not only without any
consciousness of wrong-doing, but even with the approbation of his
associates. Hence, it is the more important to establish firmly in the
public mind the well-founded opinion that the endowed professorships of
our higher institutions of learning are offices of public trust, to be
administered solely for the public good. There is no hardship in this
position; since perfectly legitimate and honorable avenues are opened to
the scientific scholar, on which he may expend his business energies,
and, at the same time, use his scientific knowledge; and for many men
these avenues lead in the directions in which they can not only most
effectually advance themselves in worldly prosperity, but also most
benefit their fellows. Among the men of practical ability who have
developed a new industry, or introduced a new invention, and who have
acquired wealth thereby, are to be found some of the greatest
benefactors of their race; and far would it be from me to institute a
comparison between the practical men and the scholars. All we claim is
that the men of affairs should resign the endowments intended for the
maintenance of scholars to those whose zeal is sufficient to induce them
to make gladly the sacrifices which the advancement of knowledge usually
entails.

These considerations will appear still more forcible if viewed in
relation to the interest of the community in scientific culture to which
we have already referred. This interest has not been overlooked, and in
recent years a great many projects have been discussed for what is
termed the "endowment of research"; and already very considerable funds
are held by learned societies of the Old World, and smaller amounts by
several societies of this country, which have been devoted to this
object. But although means are thus furnished to a limited extent to pay
the expenses of scientific investigations, and very considerable prizes
are offered for the solution of important problems, yet it must be
confessed that as yet the results have been meager and have not answered
the expectations of the founders of the endowments; and the reason of
the small fruitage is not far to seek. A certain order of scientific
results can be purchased like other professional work for a price which
is to some extent proportionate to the skill required to obtain them.
Such, for example, are the daily observations at an astronomical or a
meteorological station; such also are chemical analyses and assays of
various kinds; such, again, is much of the routine work of a physical
laboratory. But the highest order of scientific results, such as leave a
permanent impress on the records of science--like Newton's law of
gravitation, Young's theory of light, Faraday's theory of electricity,
or Bunsen's methods of spectrum analysis--can no more be had to order
than could "Paradise Lost" or "In Memoriam" have been purchased by the
foot. Moreover, scientific progress follows a necessary law of
continuity, and important advances can not be made until the time is
ripe. The most that can be done with the direct endowments for research
is, to multiply trustworthy observations, and thus prepare the way for
discovery; and more than this can not be expected.

A more efficient means of cultivating science, and one which is certain,
in the long run, to yield a far more abundant and richer harvest, is to
secure the conditions which are known to be favorable to scientific
discoveries, and to hold in honor such discoveries when made; and I
think there will be little difference of opinion among competent
scientific authorities that the one essential condition above all others
is a certain atmosphere which results from the association of men who
are engaged in scientific study.

An association of scholars acts in many ways to favor either literary or
scientific production. In the first place, it leads to competition,
which, although a low motive, is a very potent one in all forms of human
activity. In the second place, the contact of minds engaged in similar
studies leads the student to take a broader view of his subject, and to
see it from the various points of view which the criticism of his
associates may point out. Above all, work done in such associations is
not done without observation, and there are present witnesses to attest
the results, and publish them with the authority which is required to
insure for them general acceptance. A great deal of scientific work is
lost to the world because done in a corner, and buried in the
transactions of local societies, from which it is not disinterred until
the work has been repeated. The advantages of such association are only
too evident to the numerous workers in science at the isolated colleges
of this country, who are forced to compare their opportunities with
those of their compeers in the great capitals of Europe; and the want of
scientific productiveness in the United States which we so greatly
lament is due chiefly to the want of the stimulus which combined action
so greatly gives. Happily, however, the conditions favorable for
scientific investigation are multiplying at home, and already there are
several centers at which the productiveness is rapidly increasing, and
gives great promise of the future. Moreover, this growth gives us a good
indication as to the points at which we can most advantageously apply
aid; and I am confident that there is no way in which we can so
effectively encourage scientific investigation as by establishing at the
institutions of learning, which are at present the chief centers of
scientific activity, more professorships and fellowships, in order to
give support to those who are ready to devote their lives to scientific
study.

The teaching which a professorship implies, instead of being a
hindrance, ought to be a great stimulus to scientific investigation. Of
course, this influence is greatly impaired if, as in many of our
colleges, the available energies of the teacher are exhausted by the
daily routine of instruction, or by the outside work required to
supplement his meager salary. But, if the teaching is only moderate in
amount and in the direction of the professor's own work, there is no
stimulus so great as that which the association with a class of earnest
students supplies.

Were it necessary to sustain the opinions here advanced by further
illustrations, we need only point to the Royal Institution of Great
Britain, which holds foundations like those we have advocated; for the
names of Davy, Young, Faraday, Tyndal, and Dewar, are a conspicuous
memorial of the very great success of such endowments in advancing
physical science.

It is obvious, however, that the endowment of professorships and
fellowships will be of no value to the community unless it is understood
that the incumbents are set apart for their special work; and the
suggestion that such positions could be used to favor private ends, or
as the basis of mercantile transactions, is sufficient to show how
inconsistent such a practice is with the true conception of scientific
culture.

Our patent laws have a very marked and not altogether a beneficial
influence on the scientific culture of the country. It is true that they
foster mechanical ingenuity and inventive talent in certain directions,
but they also set before the people a very low and mercenary standard of
scientific attainment, upon which the popular notion of the utilitarian
tendency of scientific studies is to a great extent based. No one can
question that the discoverer of a new process, or the inventor of a new
machine, has a right to keep his knowledge to himself, and to make the
best use he can of his good fortune to increase his wealth. But
certainly the motto at the head of this essay points to a more excellent
way, and it is at least an open question whether it is for the interest
of the community at large to encourage by its laws the more selfish
course. The argument by which the patent laws are usually defended by
legal writers--that it is for the benefit of the community to encourage
and therefore to protect inventive talent--is by no means so
unanswerable as it appears _prima-facie_.

In the first place, it may be questioned whether, in the present
condition of our patent laws, they do not hinder more than they foster
invention. Any one who has attempted to perfect a machine, or improve a
chemical process, knows to what extent he is hampered on every side by
patent rights, which often have no value to the holders except that
which the new improvement may give to them.

Again, the inventions which the patent laws foster are only those having
an immediate pecuniary value, and it is often exceedingly simple
contrivances--like the needle of a sewing-machine or a gaudy toy--which
yield the greatest return; simply because they have been accommodated to
present emergencies or to passing popular fancy. Such contrivances
usually manifest no extended knowledge and no special talent, and the
inventor owes his good luck to the sole circumstance that he was in a
position to recognize the want.

Now, every scientific investigator knows that the ordinary work of a
physical or chemical laboratory frequently demands inventive ability of
a high order, and that few important scientific results have been
reached that have not involved inventions as worthy of admiration as the
sewing-machines and power-looms which are so frequently cited as
examples of the beneficent influence of our patent laws; and the
question arises, is it for the interest of the community to promote one
class of inventions more than the other? Certainly, if we consider
either the sacrifice involved, or the ultimate good which eventually
results to the community, there can not be a moment's question which
class is the most valuable or most worthy of commendation. Yet the
patent laws not only give their immense prizes solely to inventions of
immediate utility, but also tend to raise a false estimate of the
intrinsic value of such inventions in the public mind.

Some writers have gone to the extreme of claiming that a man has the
same right in his inventions or discoveries that an author has in his
books; but this claim will not bear analysis. The first duty of a
government is to protect its citizens in the enjoyment of the results
of their lawful labor, and certainly any one who has written a book
knows that it is just as much the product of day-labor as any article of
merchandise. On the other hand, an invention or discovery may be the
result of a fortunate accident, and, although it may be the fruit of
superior knowledge and intelligence, it can not be regarded in the same
sense as a direct product of labor. It is much more frequently a free
gift of Nature.

Moreover, it is seldom if ever the case that a useful invention, meeting
a popular want, and therefore having a large commercial value, is in any
sense the product of one man. As a general rule, the patentee who enjoys
the right to the invention has actually added to the old stock only a
single detail. It may be that this detail was the one thing required to
make the invention practically useful; but it is certain that the
addition could never have been made if the previous knowledge had not
existed, and it is at least an open question whether the community ought
to grant to the last man an exclusive right to the whole inheritance.
Volta discovered--invented, if you please--the mode of generating a
current of low-tension electricity, which has been ever since, with
certain modifications, in general use; Oersted and Ampére discovered the
magnetic effects of this electrical current; Faraday, again, learned how
to produce an electric current from a magnet, and invented the original
dynamo-machine; Henry discovered the conditions under which the magnetic
effects of an electric current might be produced at great distances from
the source of the power. All these men were inventors of the highest
order, whose inventions have never been excelled either in the ingenuity
displayed, or in the influence exerted on the welfare of mankind.
Moreover, these far-reaching inventions were a willing contribution to
the world's knowledge, for which no pecuniary compensation was either
asked or received. Is it not, then, a question if any man of the present
day has a right to the exclusive use of these inventions; for writing
messages at a distance, for transmitting sound over wires, or for any
purpose whatsoever?

There is of course another side to the question, and I freely admit the
difficulty of the problem which our patent laws present; but I feel that
in their present condition they do more harm than good, and do injustice
more frequently than they protect right. I greatly doubt if it is safe
to grant by statute property in any invention or discovery beyond the
definite mechanical contrivance in which it is for the time embodied. To
grant the sole use of a well-known power of Nature to produce a specific
effect, although the effect be a novel one; to give the monopoly of a
process of Nature to the man who was the first to claim it; above all,
to grant the sole right to make a specified mixture of materials--is
certainly a policy which directly encourages vast monopolies, that tax
the public without rendering a corresponding benefit.

In this connection it must be remembered that the discoverer or inventor
himself rarely reaps the fruit of his sagacity or skill; but his rights,
frequently purchased for a song, are made the basis of great business
enterprises in which he has little or no share. On such a slender basis
have frequently been built up huge monopolies, in which the patent laws
have been made the instruments of oppressive exactions, and have become
the nucleus of a most complex system of usages and legal decisions, by
which the original intent of the laws has been wholly overlaid, and to a
great extent nullified.

Certainly, there ought to be some limit to the inventor's claims on a
grateful people. Admit to the utmost the inventor's merit; rank him in
the fore front of the long procession of the great benefactors of the
human race; rank him before Faraday, before Volta, and before Newton;
rank him before Washington and the Fathers of the Republic; rank him
before the patriots and martyrs who have died in the defense of human
rights, or in attestation of the truth: and yet, in virtue of these
transcendent merits, should he or his representatives be authorized to
tax his countrymen millions on millions of dollars a year? Surely, there
could not be a greater travesty of our motto, "Noblesse Oblige"; and a
system which gives a legal sanction to such abuses will soon force on
the public mind that most convincing of all proofs of perversion, the
_reductio ad absurdum_.

It is not, however, our intention to discuss the abuses of the patent
laws, much less to suggest the required remedies. We clearly see the
difficulties of the subject, and we perceive that it involves questions,
both of political economy and of jurisprudence, with which we are not
competent to deal. Our interest is solely to maintain the dignity of
scientific culture, and to demand for it the respect to which it is
entitled; but which is seriously compromised by the mercenary and
utilitarian spirit that the patent laws encourage and make prominent. We
are most anxious that the intelligence of our people should fully
recognize the fact that, among the students of science in this practical
age, there is such a thing as devotion to the truth for the truth's
sake; that throughout the length and breadth of these United States may
be found many an earnest student of Nature who, under great
disadvantages, and often at great personal sacrifice, is devoting the
noblest intellectual power, and the highest inventive skill, to the sole
end of advancing knowledge: and we rejoice to believe that the time
will come when it will be plainly seen by all that these silent workers
have been laying broad and deep-enduring foundations, on which national
greatness can securely rest.




XIII.

THE SPIRITUAL LIFE.[Q]


We have reached the end of our long journey, and now we are ready to
turn back and start for home.

  [Q] An Address to College Students at the close of a course of
      lectures on Egypt and her Monuments. Illustrated by lantern
      photographs.

The Reis is at his helm, the great sail is furled and bound closely to
the long yard; for, as the wind during the early spring blows here
constantly from the north, we must depend on the rapid current of the
Nile to bear us back to civilization: a river which, flowing through so
many generations of men from the unknown to the unlimited, not unfitly
typifies the course of history; and as, in imagination, we drift with
this historical stream, we can not fail to learn the lesson which the
associations and the scenes are so calculated to teach. That lesson is
the grandeur, the glory, and the immortality of the spiritual life of
man.

We go back six thousand years, and find the Sphinx, as to-day, looking
toward the rising sun, and pondering the problem of human destiny.

The pyramid-builders come, and erect those neighboring piles to preserve
their bodies when dead for that glorious destiny in which they trust.

The long procession of the Pharaohs passes, and each inscribes indelibly
on rocky walls his faith in the great God who holds human destiny in his
hands.

Moses comes, and leads out of Egypt the chosen people to prepare the way
for the expected Messiah.

The Assyrians and the Persians come, and, while seeking to read their
destiny in the courses of the stars, pay homage to the same great hope.

The Greeks come, and, even amid gross licentiousness and idolatry, erect
magnificent temples, in attestation of a belief in human destiny which,
however degraded, still survived.

The Romans come, and in this mystic land lay aside their legal codes,
and add their testimony to the same great truth.

The Christian hermits come, and make the storied stones of the Pharaohs
re-echo with their triumphant songs.

The Arab comes, and, as morning and evening he gazes into the East, sees
visions of the glorious Mecca of his hopes for which the Sphinx has
looked so long.

Last of all, the modern traveler comes, and he journeys in vain if he
does not recognize in all this aspiration and all this yearning the
attestation of those spiritual truths which to him the risen Christ has
revealed.

As in material nature every unemployed organ distinctly points to a
previous use or to a future fruition: so, in the spiritual world, every
striving is a promise of a possible good; and these yearnings of
humanity, which have come down through the ages, are as truly a promise
of the Eternal as were the words spoken to Abraham on the plains of
Mamre.

Coming home from the East, we can not fail to see, more clearly than
before, how artificial are most of the conventionalities of our modern
civilization, and how greatly such cares of the world tend to obscure
the great distinction between the spiritual and the material which is
ever present to Oriental thought; and this is especially true in our own
country, where the demands of material nature are so pressing, and where
the physical wants, which our highly artificial life entails, so
completely engross the attention of us all.

It is well to go away at times, that we may see another aspect of human
life, which still survives in the East, and to feel that influence
which led even the Christ into the wilderness to prepare for the
struggle with the animal nature of man.

We need something of the experience of the anchorites of Egypt to
impress us with the great truth that the distinction between the
spiritual and the material remains broad and clear, even if with the
scalpel of our modern philosophy we can not completely dissect the two;
and this experience will give us courage to cherish our aspirations,
keep bright our hopes, and hold fast our Christian faith until the
consummation comes.

My young friends, there are many who will tell you that the Sphinx has
merely propounded a riddle to the ages; and that the yearnings of your
young lives--like those of the early Egyptians, who set up this memorial
of their hopes--are merely a delusion and a snare.

Do not believe in any such pessimism.

It is merely the dying gasp of your animal nature! But give your utmost
efforts that these aspirations be not smothered by the cares and trials
which must come to you as they come to all.

Have faith in the Eternal who implanted those cravings in your nature;
and remember that all knowledge rests on the assurance that the Eternal
can not be false. Be loyal to the truth of that witness in your hearts,
and advancing years will only bring you increased reliance on the
promises he ever whispers to those who trust him; and he will certainly
lead you, at last--as he has led the faithful in all ages--into the
clear light of the perfect day.

My fellow-students, if these fleeting pictures of scenes which have
given me fresh courage, shall aid any of you in the conflict of life, my
object in these lectures will be gained, and however incongruous with
the associations of physical science such scenes may have appeared, you
will bear me witness that the great lesson they teach has constantly
been enforced in this place. The spiritual life of man recognizes its
exalted intellectual likeness in the life of Nature, and it is this
vision of the Omniscient which distinguishes and ennobles mental
culture, whether it be in the fields of science, of literature, or of
art.


THE END.


       *       *       *       *       *


SCIENTIFIC LECTURES AND ESSAYS.

  Popular Lectures on Scientific Subjects. By H. HELMHOLTZ, Professor
    of Physics in the University of Berlin. First Series. Translated by
    E. ATKINSON, Ph. D., F. C. S. With an Introduction by Professor
    TYNDALL. With 51 Illustrations. 12mo. Cloth, $2.00.

    _CONTENTS._--On the Relation of Natural Science to Science in
    General.--On Goethe's Scientific Researches.--On the Physiological
    Causes of Harmony in Music.--Ice and Glaciers.--Interaction of the
    Natural Forces.--The Recent Progress of the Theory of Vision.--The
    Conservation of Force.--Aim and Progress of Physical Science.

  Popular Lectures on Scientific Subjects. By H. HELMHOLTZ. Second
    Series. 12mo. Cloth, $1.50.

    _CONTENTS._--Gustav Magnus.--In Memoriam.--The Origin and
    Significance of Geometrical Axioms.--Relation of Optics to
    Painting.--Origin of the Planetary System.--On Thought in
    Medicine.--Academic Freedom in German Universities.

    "Professor Helmholtz's second series of 'Popular Lectures on
    Scientific Subjects' forms a volume of singular interest and value.
    He who anticipates a dry record of facts or a sequence of immature
    generalization will find himself happily mistaken. In style and
    method these discourses are models of excellence, and, since they
    come from a man whose learning and authority are beyond dispute,
    they may be accepted as presenting the conclusions of the best
    thought of the times in scientific fields."--_Boston Traveler._

  Science and Culture, and other Essays. By Professor T. H. HUXLEY,
    F. R. S. 12mo. Cloth, $1.50.

    "Of the essays that have been collected by Professor Huxley in this
    volume, the first four deal with some aspect of education. Most of
    the remainder are expositions of the results of biological
    research, and, at the same time, illustrations of the history of
    scientific ideas. Some of these are among the most interesting of
    Professor Huxley's contributions to the literature of
    science."--_London Academy._

    "It is refreshing to be brought into converse with one of the most
    vigorous and acute thinkers of our time, who has the power of
    putting his thoughts into language so clear and forcible."--_London
    Spectator._

  Scientific Culture, and other Essays. By JOSIAH PARSONS COOKE,
    Professor of Chemistry and Mineralogy in Harvard College. 12mo.
    Cloth, $1.00.

    These essays are an outcome of a somewhat large experience in
    teaching physical science to college students. Cambridge,
    Massachusetts, early set the example of making the student's own
    observations in the laboratory or cabinet the basis of all
    teaching, either in experimental or natural history science; and
    this example has been generally followed. "But in most centers of
    education," writes Professor Cooke "the old traditions so far
    survive that the great end of scientific culture is lost in
    attempting to conform even laboratory instruction to the old
    academic methods of recitations and examination. To point out this
    error, and to claim for science-teaching its appropriate methods,
    was one object of writing these essays."


WORKS ON ASTRONOMY.

  Elements of Astronomy. By ROBERT STOWELL BALL, LL. D., F. R. S.,
    Andrews Professor of Astronomy in the University of Dublin, Royal
    Astronomer of Ireland. With Illustrations. 16mo. Cloth, $2.25.

  Elementary Lessons in Astronomy. By J. NORMAN LOCKYER, F. R. S.
    Richly illustrated, and embracing the Latest Discoveries. American
    edition. Adapted to the Schools and Academies of the United States.
    12mo. Cloth, $1.50.

  Outlines of Astronomy. By Sir J. J. W. HERSCHEL. With Plates and
    Woodcuts. Eleventh edition. 8vo. Cloth, $4.00.

  The Sun. By C. A. YOUNG, Ph. D., LL. D., Professor of Astronomy
    in the College of New Jersey. With numerous Illustrations. 12mo.
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    "Professor Young is an authority on 'The Sun,' and writes from
    intimate knowledge. He has studied that great luminary all his
    life, invented and improved instruments for observing it, gone
    to all quarters of the world in search of the best places and
    opportunities to watch it, and has contributed important
    discoveries that have extended our knowledge of it."--_Popular
    Science Monthly._

  Spectrum Analysis, in its Application to Terrestrial Substances,
    and the Physical Constitution of the Heavenly Bodies. Familiarly
    explained by Dr. H. SCHELLEN, Director der Realschule I. O. Cologne.
    Translated from the second enlarged and revised German edition by
    JANE and CAROLINE LASSELL. Edited, with Notes, by WILLIAM HUGGINS,
    LL. D. With numerous Woodcuts, Colored Plates, and Portraits; also,
    Angström's and Kirchhoff's Maps. 8vo. Cloth, $6.00.

    "This admirable work does credit to, or should we say is worthy of,
    the author, the translators, and the editor. The first part treats
    on the artificial sources of high degrees of heat and light; the
    second on Spectrum Analysis in its application to the heavenly
    bodies. We must approve the method followed in the translation and
    by the editor. In many translations the views of the author are
    suppressed, in order that the views of the translator or editor may
    be expounded; but here Dr. Huggins, however leniently such a fault
    might have been looked upon with him, has permitted the author's
    views to remain intact, clearly stating his own and wherein lies
    the difference."--_The Chemical News._

    "Certainly, as regards mere knowledge, the 'Spectrum Analysis' has
    let us into many secrets of the physical universe which Newton and
    Laplace would have declared impossible for man's intellect to
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    by some of the ablest, most patient, and most enthusiastic
    observers, and some of the keenest thinkers, at present existing
    on our little, insignificant physical globe."--_Boston Globe._

  Studies in Spectrum Analysis. By J. NORMAN LOCKYER, F. R. S.,
    Correspondent of the Institute of France, etc. With Sixty
    Illustrations. 12mo. Cloth, $2.50.

    "The study of spectrum analysis is one fraught with a peculiar
    fascination, and some of the author's experiments are exceedingly
    picturesque in their results. They are so lucidly described, too,
    that the reader keeps on, from page to page, never flagging in
    interest in the matter before him, nor putting down the book until
    the last page is reached."--_New York Evening Express._

  Origin of the Stars, and the Causes of their Motions and their Light.
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  Astronomy and Geology Compared. By Lord ORMATHWAITE. 18mo. Tinted
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  The Expanse of Heaven. A Series of Essays on the Wonders of the
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    "'The Expanse of Heaven' can not fail to be of immense use in
    forwarding the work of education, even when it is read only for
    amusement, so forcible is the impression it makes on the mind from
    the importance of the subjects treated of, while the manner of
    treatment is so good."--_Boston Traveller._

  The Moon: Her Motions, Aspect, Scenery, and Physical Conditions, with
    Two Lunar Photographs and many Illustrations. By R. A. PROCTOR. New
    edition. 12mo. Cloth, $3.50.

  Other Worlds than Ours; the Plurality of Worlds, studied under the
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  Our Place among Infinities. A Series of Essays contrasting our Little
    Abode in Space and Time with the Infinities around us. To which are
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WORKS ON GEOLOGY, Etc.

  Principles of Geology; or, The Modern Changes of the Earth and its
    Inhabitants, considered as illustrative of Geology. By Sir CHARLES
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    The "Principles of Geology" may be looked upon with pride, not only
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  Text-Book of Geology, for Schools and Colleges. By H. ALLEYNE
    NICHOLSON, M. D. 12mo. Half roan, $1.30.

  The Ancient Life-History of the Earth. A Comprehensive Outline
    of the Principles and Leading Facts of Palæontological Science.
    By H. ALLEYNE NICHOLSON, M. D. With numerous Illustrations.
    Small 8vo. Cloth, $2.00.

  Elements of Geology. A Text-Book for Colleges and for the General
    Reader. By JOSEPH LE CONTE, LL. D., Professor of Geology and
    Natural History in the University of California. With upward
    of 900 Illustrations. Revised and enlarged edition. 12mo.
    Cloth, $4.00.

  Town Geology. By the Rev. CHARLES KINGSLEY, F. L. S., F. G. S.,
    Canon of Chester. 12mo. Cloth, $1.50.

  The Study of Rocks. An Elementary Text-Book in Petrology. With
    Illustrations. By FRANK RUTLEY, of the English Geological Survey.
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  Great Ice Age, and its Relation to the Antiquity of Man. By JAMES
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  Volcanoes: What they Are and what they Teach. By J. W. JUDD,
    Professor of Geology in the Royal School of Mines (London).
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  Climate and Time in their Geological Relations: A Theory of Secular
    Changes of the Earth's Climate. By JAMES CROLL, of H. M. Geological
    Survey of Scotland. With Maps and Illustrations. 12mo. Cloth, $2.50.

  Geology. By Professor ARCHIBALD GEIKIE, F. R. S. ("Science Primers.")
    18mo. Flexible cloth, 45 cents.


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       *       *       *       *       *




TRANSCRIBER'S NOTES


1. Passages in italics are surrounded by _underscores_.

2. Footnotes have been reindexed and moved from the end of the page to
the closest paragraph break.

3. Certain words use oe ligature in the original.

4. Carat character (^) is used to indicate "raised to power". And the
underscore character (_) is used to represent subscript.

5. The greek letter alpha is represented as [alpha] in this text.

6. A mixed fraction is indicated with a hyphen and forward slash. For
example, 3-1/2 represents three and a half.

7. The following misprints have been corrected:
    "1/0000" corrected to "1/1000" (page 111)
    "strucure" corrected to "structure" (page 139)
    "fevric" corrected to "ferric" (page 141)
    "d'antorité" corrected to "d'autorité" (page 188)
    "resourses" corrected to "resources" (page 206)

8. Other than the corrections listed above, printer's inconsistencies in
spelling, punctuation, and ligature usage have been retained.