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THE

JOURNAL OF GEOLOGY

_MAY-JUNE, 1893._




CONTENTS


  On The Typical Laurentian Area of Canada                           325

  Melilite-Nepheline-Basalt and Nepheline-Basanite from Southern
      Texas                                                          340

  Some Dynamic Phenomena Shown by the Baraboo Quartzite Ranges of
      Central Wisconsin                                              347

  The Chemical Relation of Iron and Manganese In Sedimentary Rocks   356

  Some Rivers of Connecticut                                         371

  Geological History of the Laurentian Basin                         394

  Editorials                                                         408

  Reviews                                                            410

  Analytical Abstracts of Current Literature                         419

  Acknowledgments                                                    423




ON THE TYPICAL LAURENTIAN AREA OF CANADA.


The name Laurentian was given by Logan in 1854 to the great series
of rocks forming the Laurentides or Laurentian Mountains, a district
of mountainous country rising to the north of the River and Gulf of
St. Lawrence, and extending in an unbroken stretch along the shore of
the latter from Quebec to Labrador, a distance of nine hundred miles.
This district, with its continuation to the west as far as Lake Huron,
being situated in the Province of Quebec and the adjacent portion of
the Province of Ontario, and forming part of the main Protaxis of the
continent, is the “Original Laurentian Area” of Logan. The Laurentian
rocks are now known to extend far beyond the limits of this area to
the west and north, constituting, as they do, by far the greater part
of the Protaxis, and underlying (with subordinate patches of Huronian)
an area of somewhat over two million square miles.[1] The area above
referred to is, however, the one which was first studied and described;
it is the “Typical Laurentian area,” and to it the observations in the
present paper will be as far as possible confined.

A general exploration of the area in question, and a more detailed
study of a small part of it--the Grenville District--situated in the
counties of Argenteuil and Terrebonne in the Province of Quebec, was
carried out by Logan and his assistants in the early years of the
Canadian Geological Survey. An excellent résumé of the results of these
studies is given in the “Geology of Canada,” published in 1863, which
contains not only a good description of the general petrographical
character and arrangement of the rocks which make up the area, but
is accompanied by an atlas containing two maps illustrating this
description, one showing the general distribution of the Laurentian in
the eastern part of the Dominion, and the other its stratigraphical
relations in the smaller area above referred to.

As a result of these studies, Logan announced his belief that the
Laurentian System consisted of two great unconformable series of
sedimentary rocks, to which he gave the names Upper and Lower
Laurentian. The latter he considered to be divisible into a lower
and an upper portion, which sub-divisions he regarded as probably
conformable to one another. In the course of time these several series
came to be known as the Anorthosite or Norian Series, the Grenville
Series and the Fundamental or Ottawa Gneiss. Logan’s views may then be
represented as follows:

  Anorthosite or Norian Series,    Upper Laurentian.
  Grenville Series,                Upper portion }   Lower
  Fundamental or Ottawa Gneiss,    Lower portion } Laurentian.

Subsequently, in the southeastern corner of the Province of Ontario,
in the district lying to the north of the eastern end of Lake Ontario,
another series of rocks was discovered--the so-called Hastings Series.
Logan supposed this to come in above the Grenville Series, while
Vennor, who subsequently examined the district, believed it to be
equivalent to the lower part of the Grenville Series already mentioned.

When these investigations were carried out, the microscope had not
as yet been seriously employed in petrographical work. The precise
composition of many of the rocks making up the several series was not
recognized, the effects produced by great dynamic action were not duly
considered, and the foliation possessed in a high degree by some and
to a certain extent by almost all these rocks was considered, in all
cases, to be a more or less obliterated survival of original bedding.
The detailed mapping in the field, accompanied by microscopical work in
the laboratory, by which alone conclusive results can be obtained in
working out the structure of complicated areas of crystalline schists,
was not carried out, in fact in many districts the construction of
detailed maps was at that time practically impossible. It is not
surprising therefore that, although excellent in the main, some of the
results arrived at have since proved to be erroneous.

It is proposed, in the present paper, to place before the readers
of this JOURNAL in as brief a manner as possible, a general account
of the several series of rocks occurring in this area, and to point
out what, in the opinion of the present writer, seems to have been
satisfactorily established concerning the stratigraphical position and
mutual relations of these ancient rocks and what still remains to be
determined by further study, and in conclusion to give a short sketch
of the evolution of this portion of the continent.

_The Fundamental Gneiss._--Exposed over very wide stretches of country
in Canada, and making up in all probability by far the larger part of
the Archean Protaxis, is the “Fundamental Gneiss,” sometimes called,
from its great development about the upper waters of the Ottawa River,
the “Ottawa Gneiss.” It is composed essentially of orthoclase gneiss,
usually reddish or greyish in color. Of this there are a number of
varieties, differing from one another in size of grain, relative
proportion of constituent minerals and in the distinctness of the
foliation or banding. It is sometimes rich in quartz, while at other
times this mineral is present in but very small amount. It is usually
poor in mica and bisilicates. Dark bands of amphibolite are not
uncommon, while basic hornblende or pyroxene gneisses occur in some
places. Other schistose rocks are rarely found. Over great areas it is
often nearly uniform in character and possesses a foliation which can
only be recognized when exposures of considerable size are examined.
On this account it is often referred to as a granitoid gneiss, a
designation, however, which by no means accurately describes it as a
whole. At a locality cited by Sir William Logan, as one where it is
typically developed, namely, Trembling Mountain in the above mentioned
Grenville Area, it consists of a fine grained reddish orthoclase
gneiss, with distinct but not very decided foliation, containing here
and there bands of orthoclase gneiss of somewhat different character,
as well as bands or layers of a dark amphibolite.

How much of this Fundamental Gneiss really consists of eruptive
material is not known. The indistinct foliation, in many cases at
any rate, is not a survival of original bedding, but is clearly due
to movements in a plastic mass. It is often possible to recognize
the existence of an indistinctly foliated gneiss intruded into
more distinctly foliated gneiss. The gneiss, in some cases, shows
excellently well-marked cataclastic structure, while in other cases
this is not distinct. The evidence accumulated goes to show that the
Fundamental Gneiss consists of a complicated series of rocks of unknown
origin, but comprising a considerable amount of material of intrusive
character.

_The Grenville Series._--In certain parts of the Laurentian area, and
notably in the Grenville district before mentioned, the Laurentian has
a decidedly different petrographical development. Orthoclase gneiss is
still the predominating rock, but it presents a much greater variety in
mineralogical composition, and is much more frequently well foliated,
often occurring in well defined bands or layers like the strata of
later formations.

Amphibolites are abundant, also hornblende schists, heavy beds of
quartzite and numerous thick bands of crystalline limestone or marble,
all these rocks being interbanded or interstratified with one another.
In the vicinity of the limestones the variety in petrographical
character is especially noticeable; garnets often occur abundantly in
the gneiss, the quartzite and the hornblende schist, as well as in
the limestone itself, beds of pure garnet rock being found in places.
Pyroxene, wollastonite and other minerals are also abundant, while the
presence of graphite disseminated through the limestones and their
associated rocks, often in such abundance as to give rise to deposits
of economic value, is of especial significance. This mineral which
is not found in the Fundamental Gneiss, occurs usually in little
disseminated scales but occasionally in veins. The limestones are
thoroughly crystalline, generally somewhat coarse in grain and often
nearly pure. They usually, however, contain grains of serpentine,
pyroxene, mica, graphite or other minerals, of which over fifty species
have been noted. They are often interstratified in thin bands with
the gneiss, in places are very impure, and may be traced for great
distances along the strike, being apparently as continuous as any other
element of the series. This development of the Laurentian is known as
the Grenville Series, and has been considered by all observers to be
above and to rest upon the Fundamental Gneiss. In it are found all
the mineral deposits of economic value--apatite, iron ore, asbestos,
etc., which occur in the Laurentian. The rocks of this series, though
generally highly inclined, over some large areas lie nearly horizontal
or are inclined at very low angles, but even in such cases they show
evidence of having been subjected to great pressure, resulting in some
cases in the horizontal disruption of certain of the beds.

The areas occupied by the Grenville series although of very
considerable extent, being known to aggregate many thousand square
miles, are probably small as compared with those underlain by the
Fundamental Gneiss. The relative distribution of the two series has not
been ascertained except in a general way in the more easily-accessible
parts of the great Archean Protaxis. The Grenville series is known to
occupy a large part of its southern margin between the city of Quebec
and the Georgian Bay, while the discovery of crystalline limestone
in the gneiss elsewhere at several widely separated points, as for
instance on the Hamilton River in Labrador, in the southern part of
Baffin Land and on the Melville Peninsula, makes it probable that other
considerable areas will, with the progress of geological exploration,
be found in the far north. Over the greater part of the Protaxis,
however, the more monotonous development of the Fundamental Gneiss
seems to prevail.

The question of the origin and mutual relations of the Fundamental
Gneiss and the Grenville series is one about which, though much has
been written but little is known. Three views may be taken on the
matter--

(1) The Fundamental Gneiss may be supposed to contain what remains of
a primitive crust, penetrated by great masses of igneous rock erupted
through it--the whole having been subjected to repeated dynamic
action.[2] The Grenville Series may be an upward continuation or
development of the Fundamental Gneiss under altered conditions, marking
in the history of the world the transition from those conditions
under which a primitive crust formed to those in which sedimentation
under the present normal conditions took place. It would seem that if
the earth originally had a crust on which the first sediments were
deposited when the temperature became sufficiently low to permit water
to condense, that the said water, at a very high temperature and under
what are to us now inconceivable conditions but little removed from
fusion, might give rise to sediments not altogether similar to those
formed by the ordinary processes of erosion at the present time. Also
that, under the unique conditions which must have prevailed at that
early time, in the formation of a crust solidification, precipitation
and sedimentation might go on to a certain extent concomitantly,
and thus no well-defined break could be detected, or would in fact
exist, between a primitive crust formed by solidification from a fused
magma and the earliest aqueous sediments or deposits. The Fundamental
Gneiss and the Grenville Series might thus, as Logan supposed, form
one practically continuous series and represent parts of the original
crust, with the first crystalline or clastic sediments deposited on it,
the whole penetrated by eruptive rocks and folded up and altered by
repeated dynamic action at subsequent periods.

The general petrographical similarity of the two series, taken in
connection with the more varied nature of the Grenville Series, its
frequent stratified character, and the presence in it of limestones and
graphite indicating an approach to modern conditions and the advent of
life, together with the difficulty of clearly separating the two series
from one another and defining their respective limits, lends support to
this view.

(2) A second view is that the Grenville Series is distinct from the
Fundamental Gneiss reposing on it unconformably and of much more recent
age; that it consists of a highly altered series of clastic origin--the
Fundamental Gneiss having possibly some such origin as that mentioned
under the last heading, or representing a much older series of still
more highly altered sediments. This is supported by the fact that
some observers have thought they could in places trace out a line of
contact between the two. But in these cases it always becomes a matter
of serious doubt whether what has been considered to represent the
Fundamental Gneiss is not really a mass of intrusive rock, in which,
by pressure or motion, a somewhat gneissic structure has been induced.
If the Fundamental Gneiss, moreover, was ever an ordinary sediment,
it must have undergone a metamorphosis so profound that no trace of
clastic origin remains, unless the generally indistinct foliation or
banding of some portions of it be considered as such. It must also be
noted in this connection that, although the rocks of the Grenville
series are more frequently possessed of a decided foliation and are
often banded, bands of different composition alternating with one
another as in ordinary sedimentary deposits, and although in this
series crystalline limestones and quartzites occur, we have as yet no
absolutely conclusive proof that even they are of sedimentary origin.
The series is thoroughly crystalline, most of its members at least show
the effect of great dynamic action, and so far as the present writer is
aware, no undoubted conglomerate or finer grained rock showing distinct
clastic structure has ever been found. In view of this fact,--although
the series is, in all probability, made up in part at least and perhaps
wholly of sedimentary material,--the proposal to separate it from the
rest of the Laurentian and class it as Algonkian or Huronian seems at
least premature.

(3) A third view which has been advanced is that the Fundamental Gneiss
is nothing more than a great mass of eruptive granite or granitic
rock which has eaten upward, and in places penetrated the Grenville
series, or perhaps absorbed it, while the Grenville series itself
represents a series of highly altered sediments of Laurentian, Huronian
or subsequent age. The enormous extent and world-wide distribution
of the Fundamental Gneiss forming as it does wherever the base of
the geological column is exposed to view, the foundation or floor on
which all subsequent rocks are seen to rest, is opposed to this view
of its origin, as is also its persistent gneissic or banded character,
although, as above mentioned, much eruptive material is undoubtedly to
be found in it.

Which of these views is correct can be ascertained only as very careful
and detailed mapping, accompanied by accurate petrographical study,
is proceeded with. In the present state of our knowledge additional
argument and discussion will not help us toward the goal, while hasty
work and generalization serves but to retard the progress of our
knowledge.

_The Anorthosite Series._--Associated with both the series of rocks
just described there are, as has been mentioned, great eruptive masses
of granite, some of which have been folded in with the gneisses, while
others evidently erupted at a much later date, show no trace of dynamic
action.

In addition to these, basic eruptive rocks belonging to the gabbro
family occur in certain districts, sometimes in the form of
comparatively insignificant masses, but elsewhere underlying great
tracts of country. One on the upper waters of the Saguenay has an area
of no less than 5,800 square miles. These usually consist of a variety
of gabbro in which the magnesia-iron constituents are present in very
small amount, being in many cases entirely wanting, so that the rock
consists practically of pure plagioclase feldspar. These rocks were
called _anorthosites_ by Hunt, in the early reports of the Canadian
Geological Survey, on account of the great preponderance in them of
“Anorthose,” a general name given many years ago by Delesse to the
triclinic feldspars, as distinguished from “Orthose,” or orthoclase
feldspar, and thus equivalent to the term plagioclase now in general
use, but having no connection with anorthite, a variety of plagioclase
which is seldom present. After a careful study of these rocks, both
in the field and the laboratory, it is believed that this name should
be retained for this well-marked member of the gabbro family, which,
though not a common rock elsewhere, has an enormous distribution in the
Laurentian of Canada.

If an olivine gabbro be regarded as the central member, so to speak,
of the gabbro family, the replacement of the monoclinic by rhombic
pyroxene will give rise to an olivine norite. A gradual diminution in
the amount of plagioclase will give rise to a peridotite or gabbro
pyroxenite, a diminution in the amount of pyroxene to a troktolite or
plagioclase-olivine rock, while a diminution in the amount of olivine
and pyroxene will give rise to an anorthosite, which variety forms
the greater part of the intrusive masses in question. The gradual
passage of one variety into another can be distinctly traced in many
localities in the anorthosite masses. These anorthosites are in some
places massive, but very frequently show a distinct foliation, often
very perfect. In some places they occur interbanded with the gneiss and
crystalline limestone, while elsewhere they cut directly across the
strike of these rocks. The interbanded anorthosite, together with the
gneiss and limestone associated with it, was supposed by Logan to form
a distinct sedimentary series, to which the name “Upper Laurentian,”
or “Norian,” was given, because the discovery that elsewhere the
anorthosite runs across the strike of the gneiss was supposed to
indicate that this series covered up and unconformably overlay
the Grenville series, the igneous and intrusive character of the
anorthosite not being recognized on account of its frequently foliated
structure. It is now known that these anorthosites do not constitute an
independent formation, but are igneous rocks which occur, cutting both
the Grenville series and the Fundamental gneiss. They have, however,
in many cases been intruded before the cessation of the great dynamic
movements to which the Laurentian was subjected in pre-Cambrian times,
and thus frequently taking a line of least resistance and having been
intruded between the bands or strata of the Grenville series, have had
a foliation induced in them parallel to that of the gneiss, while in
other cases where they are more or less massive, they cut across the
strike of the latter.

In many cases the anorthosites which exhibit a perfect foliation may be
traced step by step into the massive variety, the gradual development
of a foliated structure in the rock being accompanied by a progressive
granulation of the constituents, most beautifully seen under the
microscope. The change, however, differs from any hitherto described
in that it is purely mechanical. There are no lines of shearing with
accompanying chemical changes, but a breaking up of the constituents
throughout the whole mass, though in some places this has progressed
much further than in others, unaccompanied by any alteration of augite
or hypersthene to hornblende, or of plagioclase to saussurite, these
minerals, though prone to such alteration under pressure remaining
quite unaltered, suffering merely a granulation with the arrangement
of the granulated material in parallel strings. This process can be
observed in all its stages, and there is reason to believe that it
has been brought about by pressure acting on the rocks when they were
deeply buried and very hot.[3] The anorthosite areas, of which there
are about a dozen of great extent with many of smaller size, are
distributed along the south and southeastern edge of the main Archean
Protaxis from Labrador to Lake Champlain, occupying in this way a
position similar to that of volcanoes along the edge of our present
continents. Curiously enough precisely similar occurrences of this
anorthosite have been found in connection with similar gneissic rocks,
supposed to be of Archean age, in Russia, Norway and Egypt. These
anorthosite rocks being intrusive, may be left out of consideration in
endeavoring to work out the succession of the Archean in this great
area.

The whole Laurentian system, including the anorthosites, is in many
places cut by numerous dykes of large size, which can often be traced
for great distances. These are of several kinds, the principal series
consisting of a beautiful fresh diabase often holding quartz in
considerable amount in micro-pegmatitic intergrowths with plagioclase.
Other sets of dykes and eruptive masses consisting of augite and mica
syenites, quartz-porphyries and other rocks are also known to occur but
have not as yet been carefully studied.

_The Hastings Series._--The stratigraphical relations of the Hastings
series have not as yet been satisfactorily determined. The rocks
constituting the series differ widely in petrographical character from
those of the Fundamental Gneiss and the Grenville series, both of
which are supposed to occur in its immediate neighborhood. The series
consists largely of calc-schists, mica-schists, dolomites, slates and
conglomerates, thus containing much material of undoubtedly clastic
origin. It has moreover a very local development, being confined, so
far as at present known, to one small corner of the area, as has been
mentioned. It was by Logan supposed to come in above the Grenville
series, while Vennor who subsequently examined the district, believed
it to be equivalent to the lower part of this series. That we have in
the Hastings series a comparatively unaltered part of the Grenville
series, made up largely of rocks whose origin is easily recognized,
would be a most important fact if established, and would, of course,
afford a key to the whole question of the origin of the latter. This
is a conclusion, however, which cannot be accepted until supported by
very clear and decisive evidence, especially as the stratigraphy of the
Hastings district is very complicated, the several series represented
in it being much folded and penetrated by great masses of eruptive
rocks. The whole district has also been subject to great dynamic
action, some of the pebbles in the conglomerates of the Hastings series
being distorted in a most remarkable manner. This series may prove
to be merely an outlying area of Huronian rocks folded in with the
Laurentian, and until the district has been studied in detail its
stratigraphical position must remain a matter of conjecture.

Leaving the Hastings series out of consideration therefore, we have
in this Original and Typical Laurentian area two developments of the
Laurentian, generally considered as constituting two series, namely the

  Grenville or Upper series,
  Fundamental, Ottawa, or Lower Gneiss.

_The Evolution of the Area._--In endeavoring to outline the main
events in the evolution of this area it will be necessary to extend
the limits of our observation somewhat and seek for evidence bearing
on the question in other parts of the Protaxis, where we meet with
developments of Huronian and various earlier Paleozoic strata not found
in the typical area itself.

From the highly contorted condition of the Laurentian rocks of this
area as well as from the abundant evidences of dynamic action which
they present both in the field and under the microscope, it is evident
that they have been subjected to great orographic forces, which in
very early times threw them up into mountain ranges, probably of
great height. Some of the associated eruptive rocks were intruded
before these movements began, or while they were in progress and have
accordingly been influenced by them, while others, having been intruded
later, have not been affected.

How high these mountains rose cannot of course be determined. Bell
states that some of the mountains on the Labrador coast now rise to a
height of from 5,000 to 6,000 feet, while Lieber has estimated that on
the coast of Northern Labrador they rise to a height of from 6,000 to
10,000 feet. Along the southern part of the Protaxis, where the country
is much lower, notwithstanding the enormous subaerial denudation and
glaciation which the area has repeatedly undergone, there are many
points still rising from 2,500 to 3,500 feet above sea level, while
Logan estimated that the average elevation is from 1,500 to 1,600 feet.
In the Adirondacks, which are but an outlying portion of this area,
there are elevations of over 5,400 feet. The high elevations attained
by these rocks in portions of the Protaxis in the north may, of course,
be due to differential elevation, but immediately along the southern
edge of the area there can have been but little differential change of
level as compared with the flat-lying Potsdam strata which border it
and lie but little above the present sea level. Further evidence of
the original height or continued uprising of the area is afforded by
the fact that all the material of which the North American continent
was built up (with the possible exception of some of the limestones)
was derived originally from the Archean Protaxis of the continent, a
considerable proportion of this at least coming from the main Protaxis
of which this typical Laurentian area forms a part. We must conclude
therefore that in early Cambrian or pre-Cambrian times, in portions of
the Protaxis at least, the Laurentian mountains rose several hundred
and possibly in places several thousand feet above the sea level.

The intrusion of the granites and anorthosites as well as the folding
of the whole system of rocks took place before Upper Cambrian times.
The whole series was moreover without doubt at that time in the
“metamorphic” condition in which we now find it, for along the margin
of the area the Potsdam sandstone rests in flat undisturbed beds on the
deeply eroded remnants of these old mountains, its basal beds often
consisting of a conglomerate with pebbles of the underlying gneissic
rocks. These Cambrian strata cover up the gneisses, granites and
anorthosites alike and are evidently of much more recent age, being
separated from the Laurentian by the long interval occupied in the
upheaval and erosion of the Laurentian area.

How long before Upper Cambrian times this folding and erosion took
place cannot be determined from a study of this area, but further west
along the edge of the Protaxis in the Lake Superior district we find
that the Keweenawan, Nipigon and Animikie Series also repose in flat
undisturbed beds on the eroded remnants of a series of crystalline
rocks which have the petrographical character of the Fundamental
Gneiss. This makes it at least very probable that in this eastern area
also the erosion took place in pre-Cambrian times.

It is a very remarkable fact that the roche moutonné character
possessed by these eroded Laurentian rocks and which is usually
attributed to the glaciation which they underwent in Pleistocene
times, was really impressed upon them in the first instance in these
pre-Cambrian times, for all along the edge of the nucleus from Lake
Superior to the Saguenay, the Paleozoic strata, often in little
patches, can be seen to overlie and cover up a mammillated and roche
moutonné surface showing no traces of decay and similar to that exposed
over the uncovered part of the area. The conclusion therefore seems
inevitable that not only were these Laurentian rocks sharply folded
and subjected to enormous erosion, but that they had given to them in
pre-Cambrian times their peculiar hummocky contours so suggestive of
ice action.[4] The pre-Paleozoic surface of the Fundamental Gneiss of
Scotland, as Sir Archibald Geikie has shown, also presents the same
hummocky character.[5] On this surface the Upper Huronian, Cambrian,
and later Paleozoic rocks were deposited.

To what extent the seas of Cambrian, Silurian and Devonian times passed
over this area cannot be determined with certainty. A great series of
rocks referred to by Dr. G. M. Dawson as probably of Lower Cambrian
age and analogous in character to the Keweenawan and Animikie series
occur overlying the Laurentian in many parts of the Protaxis, not only
along its margin, but as outliers at many places in the interior. It
occurs extensively developed about the Arctic Ocean and about Hudson’s
Bay, and a large area of rocks referred to the same age also occur near
the height of land about Lake Mistassini. “Throughout the whole of
the vast northern part of the continent this characteristic Cambrian
formation, composed largely of volcanic rocks, apparently occupies the
same unconformable position with regard to the underlying Laurentian
and Huronian systems. Its present remnants serve to indicate the
position of some of the earliest geological basins, which from the
attitude of the rocks appear to have undergone comparatively little
disturbance. Its extent entitles it to be recognized as one of the
most important geological features of North America.”[6] It would,
therefore, seem that in Cambrian times a not inconsiderable part of
the Archean Nucleus was under water. Outliers of Cambro-Silurian age
are also found at several points lying well within the margin of
the Nucleus, as for instance in the Ottawa River about Pembroke at
a distance of fifty miles, and at Lake St. John at the head of the
Saguenay River at a distance of one hundred and thirty miles from its
present limit. There is reason to believe that a similar outlier exists
in the interior of the northern part of the Peninsula of Labrador, so
that the Lower Paleozoic sea must also have covered considerable areas
in the eastern half of the Protaxis, where now nothing but Laurentian
is to be seen. In that portion of the Protaxis lying to the west of
Hudson’s Bay strata of Cambro-Silurian and Devonian age extend up from
the basin of Hudson’s Bay on the east and from the great plains on the
west far over the Laurentian Plateau and probably, according to Dr.
Dawson, originally inosculated. Strata of Upper Silurian and Devonian
age are not known to exist in the eastern half of the Protaxis, of
which the typical Laurentian area forms part, with the exception of a
small outlier of Niagara age on Lake Temiscamangue at the head waters
of the Ottawa--neither do any other deposits of later age occur with
the exception of the Glacial Drift. What evidence there is, therefore,
would rather indicate that the area, during late Paleozoic, Mesozoic
and earlier Tertiary times, was out of water. If so, it must have
undergone during this great lapse of ages a process of deep seated
decay and denudation, culminating in the extensive glaciation to which
it was subjected in Pleistocene times.

During this latter period the whole area was exposed to ice action,
with the exception of the highest part of the Nucleus--the mountains
of the Labrador coast--which, except toward the base, are still
“softened, eroded and deeply decayed.”[7] This extensive denudation
served to remove all but mere remnants of any Paleozoic strata
originally deposited on the Archean of this area, while the deep decay
of the Archean rocks themselves would account for the immense numbers
of gneiss bowlders in the drift, which in all probability are but
smoothed cores of “bowlders of decomposition.” That an immense amount
of material was removed from the surface of the area during the glacial
age is shown by the immense quantities of Archean material which occurs
scattered over the surface of the Nucleus itself, as well as in the
drift to the south. The glaciation, with the depression and uplift
which succeeded it, was the last episode in the evolution of this
“original” Laurentian area and one which impressed upon it its present
surface characters and type of landscape.

It is now an immense uneven plateau, comparatively slightly accentuated
except along the Labrador coast. The surface is covered with glaciated
hills and bosses of rock with rounded, mammilated, flowing contours
interspersed with drift covered flats and studded with thousands upon
thousands of lakes great and small. A country which in the far north is
often bleak and desolate, but to the south, where it is covered with
luxuriant forest, is often of great beauty, especially when clothed
with the brilliant foliage of autumn. Even now, however, it is passing
into a further stage of its history, the smooth or polished glaciated
surfaces are becoming roughened by decay, the softer gneissic and
limestone strata are again commencing to crumble into soil, and a new
epoch has been inaugurated in which the marks of the ice age are being
gradually effaced.

                    FRANK D. ADAMS.

MCGILL UNIVERSITY.


FOOTNOTES

    [1] Accepting the distribution of the Laurentian in the far north,
        given by Dr. G. M. Dawson, as correct, the area is 2,001,250
        square miles. This does not include the outlying and separated
        areas occurring in Newfoundland, New York State and Michigan.

    [2] See also, The Geological History of the North Atlantic, by Sir
        William Dawson, Presidential Address, B. A. A. S., 1886.

    [3] See FRANK D. ADAMS--_“Ueber das Norian oder Ober-Laurentian
        von Canada,” Neues Jahrbuch für Mineralogie, etc., Beilageband
        VIII., 1893._

    [4] A. C. LAWSON.--“Notes on the Pre-Palaeozoic surface of the
        Archean Terranes of Canada.” Bulletin of the Geological Society
        of America. Vol. 1, 1890.

    [5] “A Fragment of Primeval Europe.” Nature, August 26, 1888.

    [6] G. M. DAWSON.--“Notes to accompany a geological map of the
        northern portion of the Dominion of Canada.” Report of the
        Geological Survey of Canada, 1886. p. 9, R.

    [7] ROBERT BELL.--“Observations on the Geology etc., of the
        Labrador Coast, Hudson’s Strait and Bay.” Report of the
        Geological Survey of Canada. 1882–3–4, p. 14, DD.




MELILITE-NEPHELINE-BASALT AND NEPHELINE-BASANITE FROM SOUTHERN TEXAS.


These basaltic rocks were collected by Professor Dumble and Mr.
Taff, in Uvalde County, southern Texas. On the geological map of the
United States, compiled by C. H. Hitchcock, 1886, there are two of
the localities marked near the boundary of the Cretaceous and earlier
Tertiary formation, between 99° and 100° longitude, and on the 29th
degree of latitude. According to the statement of Professor Dumble,
one part of the rocks appears in dikes in the upper portion of the
lower Cretaceous formation, while the other forms hills and buttes.
Upon microscopical examination it is evident that the specimens
collected belong to two different groups of rocks. The microscope shows
that those occurring in dikes consist of typical melilite-bearing
nepheline-basalt, while those making up hills and buttes are
nepheline-basanites tending toward phonolites in composition.

The melilite-nepheline-basalts have a typical basaltic appearance. In a
dense black groundmass, the only phenocrysts seen by the naked eye are
numerous olivines. Under the microscope there appear in addition to the
olivine the following minerals: augite, nepheline, melilite, magnetite
and perovskite. As to the proportion of nepheline and melilite, it can
be said, that in nearly all the specimens examined, the two minerals
are found in about the same amount. For this reason these rocks can
be placed under the head of nepheline-basalt as well as under that
of melilite-basalt, or they may be called melilite-nepheline-basalt.
Only one of the specimens is entirely free from melilite. Feldspar is
wholly wanting. All of the specimens are in a very fresh condition, and
even the melilite shows only slight indications of decomposition. The
specimen free from melilite corresponds in structure and composition
with the other specimens, except for the absence of melilite and
perovskite, and so they may be described together.

All the rocks are porphyritic, since they bear large phenocrysts of
olivine. Under the microscope the olivine is colorless and transparent,
and only shows indications of serpentinization along the edges and
fissures. It contains rounded inclusions of glass, abundant in some
sections, besides octahedrons of magnetite, and others that are
transparent with a brownish violet color. Whether the latter are a
mineral of the spinel-group or belong to perovskite, with which they
accord in color, could not be decided.

Augite occurs in only one generation; phenocrysts of augite are
wanting. In the rather coarse-grained groundmass, it becomes the most
abundant constituent. The mineral shows a grayish-brown color, common
to basaltic augite, sometimes with a tint of violet. It generally forms
well-shaped crystals, rarely irregular grains, and bears inclusions of
magnetite and glass.

Melilite occurs in the groundmass in large and well-shaped crystals,
its dimensions never becoming as small as those of many of the augite
crystals. They may be designated as micro-porphyritical phenocrysts.
Cross sections parallel to (001) reach a diameter of 0.5 mm. The
shape of the melilite is the common one, tabular parallel to (001).
The diameter of the tables generally exceeds their thickness from
four to six times. Sections parallel to the prism-zone, therefore,
are lath-shaped and the vertical axis lies perpendicular to their
length; the axis of greatest elasticity coincides with the vertical
axis. Between crossed nicols these sections show the particular blue
interference colors characteristic of melilite and zoisite. Sections
perpendicular to the prism-zone are eight-sided by reason of the planes
(110) and (100), but frequently the outlines are rounded. In some
of the sections examined the melilite incloses minute opaque grains
arranged zonally, which present very sharply the prismatic outlines of
their host. Besides the two prismatic faces above mentioned, there is
also a ditetragonal prism, the angle of which upon the adjoining faces
of (110) and (100) was found to be nearly equal, 20°-22°. According
to this measurement the prism must have approximately the position of
(940); the angle of the latter upon (110) is 21° 2´, the angle upon
(100) = 23° 58´. A particular phenomenon in the growth of the melilite
is the fact that the base does not generally present an even plane, but
shows a conical depression. The shape of the lath-shaped sections then
resembles the profile of a biconcave lens. Sections parallel to the
base are isotropic between crossed nicols and show, when they are not
too thin, an indistinct dark cross in convergent light. The cleavage
parallel to (001), the cross-fibration of the lath-shaped sections
and the occurrence of the spear-shaped and peg-shaped inclusions
arranged parallel to the _c_ axis (the so-called _Pflockstruktur_)
are very distinct. Inclusions of pyroxene, magnetite and glass are
common; as already mentioned, these inclusions are generally arranged
in zones. In sections parallel to (001) they fill the central parts
of their host, and often make up two or three concentric zones. These
sections closely resemble leucite because of their rounded shape,
the arrangement of the inclusions and the lack of double refraction.
Melilite becomes nearly colorless and transparent, but in comparing it
with the white, colorless nepheline, it shows a feeble yellow tint.
Decomposition has taken place to only a small extent; it begins along
the cross-fibration, and greenish-yellow alteration-products result,
the fibres of which are perpendicular to the length of the lath-shaped
sections.

Nepheline is always fresh, colorless and transparent; it rarely
exhibits a regular shape, but generally forms an aggregate of irregular
grains, cementing the other components; it is evidently the latest
formed mineral in the rock.

There is abundant magnetite besides perovskite, the common associate of
melilite, which occurs in small octahedrons and irregular grains. The
perovskite becomes transparent with a brownish-violet color, and shows
in some sections a feeble, abnormal double refraction. There appears
to be no isotropic base in the normal rock, but if any is present, it
must be in a very small amount. There are coarser grained spots in
the rock, which are rich in a partly chloritized base, and in which
nepheline occurs in well-shaped crystals.

The second group of rocks, as already mentioned, falls under the
head of nepheline-basanite poor in olivine. And since the specimens
bear sanidine phenocrysts beside plagioclase, it forms a transition
to phonolite. The rock-specimens have a more andesitic than basaltic
appearance. Numerous phenocrysts of hornblende and augite are imbedded
in the dense bluish-gray groundmass. The next most abundant mineral is
nepheline in the form of phenocrysts, in part well-shaped crystals,
in part rounded, the largest of which are 0.5 cm. in diameter. The
nepheline differs from the feldspar in having a grayish color and
greasy lustre. Phenocrysts of feldspar and crystals of olivine are
scarce. Beside these components, the rocks contain apatite, some
titanite and iron ores. Under the microscope olivine is seen to be
scarce. It is fresh and shows the normal properties. It contains minute
octahedrons of picotite and in some sections abundant inclusions of a
liquid with moving bubbles.

The amphibole mineral is a typical basaltic hornblende. It becomes
transparent with a dark reddish-brown color and exhibits a strong
pleochroism according to the following scheme:

=a=, brownish yellow, =b= and =c= dark reddish brown. Absorption,
=c > b > a=.

The angle of extinction was examined in sections cut approximately
parallel to the clinopinacoid (010) and was determined to be very
small. This fact and the dark reddish-brown color are in all
probability due to a high amount of Fe₂O₃. The dependence of the angle
of extinction upon the amount of Fe₂O₃ in minerals of the amphibole
group has been recently established by Schneider and Belowsky. The
basaltic hornblende shows the well-known dark borders produced by
reabsorption by the magma in an early stage of consolidation. In
many cases nothing of the original mineral is preserved; the whole
hornblende is replaced by a fine grained aggregate of pyroxene and
magnetite, presenting clearly the outlines of the absorbed mineral.

The group of pyroxenic minerals is represented by two monoclinic
augites. One of them exhibits a violet-gray color in thin section and
belongs to the basaltic augites; the other one becomes transparent
with a dark green color. Both form numerous phenocrysts, but the first
occurs somewhat more frequently. They occur as single crystals and are
also grown together in a zonal manner, the green one always forming the
center, the gray one the outer parts of the crystals. Hence the gray
augite is the younger. The pyroxene in the groundmass shows the same
color and properties. The pleochroism of the two minerals is as follows:

  Gray augite.            Green augite.
  =a= Brownish-yellow     Light yellowish-green
  =b= }                   Dark gray-green
  =c= } Violet-gray       Dark green.

The angle of extinction, _c_: =c=, is large and, as may be seen in the
zonal crystals, it is somewhat larger in the gray pyroxene than in the
green. The extinction in sections cut approximately parallel to (010)
has been observed to be about 47 degrees (gray augite) and 41 degrees
(green augite). The two pyroxenes show in addition to the cleavage
parallel to (110) another but less distinct one parallel to (010).
Inclusions of magnetite, apatite and glass are common.

Phenocrysts of feldspar are scarce. In part they show the polysynthetic
twinning lamination of plagioclase; in part the latter is wanting
and one of the latter feldspars, which was isolated and examined for
specific gravity and optical properties, was found to be sanidine.
Phenocrysts of nepheline are more frequent than those of feldspar.
The mineral appears partly in the form of short-prismatic crystals,
partly in rounded grains. It presents distinct cleavage, parallel to
(1010) and to (0001), and the usually observed optical properties.
Isolated grains are decomposed by hydrochloric acid with the separation
of gelatinous silica; the resulting solution when evaporated gives
numerous cubes of NaCl. Inclusions are scarce; there are fluid cavities
with moving bubbles, generally arranged in rows, besides some pyroxene
crystals.

Apatite forms short and stout crystals always filled with inclusions
of liquids. The opaque ore grains, judging by their ready solubility,
belong to magnetite. The groundmass of these rocks consists essentially
of pyroxene in well-shaped prisms, lath-shaped feldspar, without
twinning lamination or in single twins according to the Carlsbad law
and nepheline. The feldspar of the groundmass in all probability is
mostly sanidine. Nepheline is abundant and occurs in well-shaped
crystals. Small patches of a colorless base occur between the
crystalline components.

The structure of the rocks is hypocrystalline-porphyritic on account
of the occurrence of an isotropic base and the repetition of the
crystallization of pyroxene, nepheline and feldspar. Although the
specimens by their whole habit and structure belong under the head
of nepheline-basanite poor in olivine, the presence of sanidine
as phenocrysts causes them to form a transition to the group of
phonolites. Unfortunately, analyses of these rocks have not yet been
made.

A microscopical examination of the basaltic rock from Pilot Knob, near
Austin, Travis County, was made for the purpose of comparison with the
rocks from southern Texas just described. The rock was found to be a
nepheline-basalt porphyritic with numerous phenocrysts of olivine.
The fine grained groundmass consists essentially of augite-crystals
cemented by non-individualized nepheline in very small amount.

                    A. OSANN.




SOME DYNAMIC PHENOMENA SHOWN BY THE BARABOO QUARTZITE RANGES OF CENTRAL
WISCONSIN.


The quartzite ranges of Baraboo extend east and west for about thirty
miles, one lying north, and the other, the main range, lying south of
the City of Baraboo. The geology of this district is admirably given by
the late Professor Irving.[8] Not only is the general geology clearly
described, but remarkably accurate descriptions are given of the
character of the quartzite, and the phenomena shown by it, considering
the fact that the report was written nearly twenty years since. The
unconformity existing between the quartzite and the Cambrian was later
more fully described.[9] The induration of the Baraboo quartzite has
been explained as due to the enlargement of the original quartz grains;
and to the deposition of independent interstitial quartz.[10] The
present note is based upon recent observations on the East Bluff at
Devil’s Lake and on the exposures at the Upper Narrows of the Baraboo
River.

The section across the ranges, as given by Irving, is shown by Fig. 1.
The two ranges together, as thus represented, are less than the north
half of a great anticline, the south side of the south range being near
its crown. This structure involves a very great thickness of quartzite,
and was offered with reservation by Professor Irving. He says: “The
hypothesis is not altogether satisfactory. The entire disappearance of
the other side of the great arch, as well as the peculiar ways in which
the ranges come together at their extremities are difficult to explain
by it. It may be said in this connection that the dip observations
toward the west are not so satisfactory or numerous as they might be.”
The question naturally arises whether or not the great width of the
ranges in the central part of the area may not be partly explained by
monoclinal faulting, and thus reduce the supposed thickness of the beds.

[Illustration: FIG. 1.--Ideal Sketch, showing structure and amount of
erosion of the Baraboo Ranges.

After Irving.

Scale natural, 12,000 feet to the inch.]

The layers of quartzite are ordinarily very heavy, but the changing
character of the original sediment is such as to make it easy to
follow the layers. Some beds were composed of fine grains of quartz,
mingled with clayey material, others of coarse grains with little
clayey material, and others of pebbles so large as to pass into an
unmistakable conglomerate. The pebbles of the conglomerate are mainly
white quartz and red jasper. It is thus easy to discriminate the
bedding of the series from the heavy jointing which occurs, cutting
the bedding in various directions, and from a secondary cleavage and
foliation which occurs in certain localities.

From the general work of many geologists on dynamic action in folding,
it is to be expected that the amount of movement necessary for
accommodation between beds, and consequently the dynamic metamorphism
resulting from shearing, would be less near the crown of the anticline
than on the leg of the fold. That is, dynamic metamorphism ought
not to be so extensive in the south range as in the north range. The
facts described by Irving,[11] and those noted by me, fully agree with
this anticipation. The central parts of the heavy, little inclined
beds of the south range are largely indurated by simple enlargement.
The pressure has not been sufficient to obliterate the cores, but has
apparently granulated the exterior of some of the larger fragments, as
in hand specimens the exteriors of the large blue quartz grains are
white. Very generally the grains show slight wavy extinction. A few of
them are distinctly cracked. The crevices thus formed and those in the
interstices have been filled in large part by infiltrated silica, but
their positions are plainly indicated by difference in extinction, by
bubbles, by iron oxide, or by secondary mica which has taken advantage
of the minute crevices.

However, as described by Irving, between the heavy beds of quartzites
are often layers, cut by a diagonal cleavage which dies out in passing
into the thick beds. The layers showing cleavage sometimes pass into
those showing the beginning of foliation, the rock then nearing a
schist. In the centers of the schist zones, the schistosity approaches
parallelism with the bedding, and in passing outward curves from this
direction until it crosses the bedding at an angle, at the same time
becoming less marked and grading into ordinary cleavage, which dies out
in the quartzite. Upon the opposite side the transition is of the same
character, but the curve is in the opposite direction.

Irving apparently regarded these shear zones as originally beds of a
different character from the adjacent quartzite, and his conclusion is
fully borne out by the thin sections. The microscope shows that the
grains of quartz are of small size, and separated to a greater or a
less extent by interstitial clayey material. Because of this partial
separation of the grains of quartz, they have not been granulated to
the extent that one would expect from the schistosity of the rock, most
of the original cores being plainly visible. They, however, often show
wavy extinction and even cracks, but not to a greater degree than the
grains in the massive quartzite; for in the latter the full stress of
the pressure has been borne by the grains in full touch, not separated
by a plastic matrix, as are the grains of quartz in the argillaceous
layers. In the matrix of the schist are numerous small flakes of
muscovite, arranged with their longer axes in a common direction, much
finely crystalline quartz, and a good deal of iron oxide.

It is concluded that the clayey character of the beds, and,
consequently, the greater ease of movement within them, has located the
slipping-planes and shear-zones, necessary in order to accommodate the
beds to their new positions. On the south range, near Devil’s Lake,
these shear-zones are generally not more than six or eight inches
wide. They may be well seen just back of the Cliff House, and on the
Northwestern Railway, about one-half mile south of this house. All of
these shear-zones are parallel with the bedding, and illustrate the
possibility, so far as I know first mentioned by H. L. Smyth, that
a crystalline schist, with schistosity parallel to bedding, may be
produced by shearing along the bedding-planes.

On the railroad track, near the locality where these shear-zones may
be seen, is also an almost vertical shear-zone, two to four feet wide.
It therefore cuts almost directly across the beds of quartzite, which
here incline to the south about twelve or thirteen degrees. Throughout
this band, the quartzite is broken into angular trapezoidal fragments,
the longer directions of which are vertical, and which may be picked
out with the hammer. In certain parts of the zone well-defined gruss
or friction clay produced by the grinding of the fragments against one
another, has been produced. This is clearly a plane of faulting. How
much the throw of this fault is it is not easy to say, as the heavy
beds of quartzite are so similar that it is impossible to certainly
identify them. At this place there is, however, a change in the
character of the quartzite, layers of light color being overlain by
other beds, which are more heavily stained with iron oxide. This same
succession is seen on both sides of the fault, and if beds of like
character correspond, the amount of the throw is twenty to thirty feet,
and the south side has dropped relative to the north side. In other
words, the faulting is in the right direction to reduce the theoretical
thickness of the sediments as given by Irving. The district has not
been closely examined for other faults, but the existence of one fault,
even of a minor character, suggests that a careful study of the whole
area with reference to faulting should be made, in order to determine
what deductions may possibly be made from Irving’s estimate of the
probable thickness of the quartzite.

At the upper narrows of the Baraboo, near Ablemans, we are on the north
leg of the anticline. The dip is throughout from seventy to ninety to
the north, and in some places the layers are slightly overturned. The
slipping along the bedding has here been much greater. While in this
area there are heavy beds of quartzite which have not suffered great
interior movement, other beds have been sheared throughout, being
transformed macroscopically into a quartz-schist, but the foliation
is strongly developed. In other places, as described by Irving,[12]
where the rock is a purer quartzite, for a distance of 200 feet or more
across the strike, the rocks have been shattered through and through,
and re-cemented by vein quartz.

For the most part the rock is merely fractured, the quartz fragments
roughly fitting one another, but there are all gradations from this
phase to a belt about ten feet wide of true friction conglomerate, the
fragments having been ground against one another until they have become
well-rounded (a Reibungs breccia). Between the boulders of this zone
is a matrix, composed mainly of smaller quartzite fragments. The whole
has been re-cemented, so that now the mass is completely vitreous. This
belt of friction conglomerate at first might not be discriminated from
the Potsdam conglomerate, immediately adjacent, but a closer study
shows how radically different they are. In one the cementing material
is vein-quartz; in the other the sandstone has been feebly cemented by
quartz enlargement.

A movement later than the one which produced the cemented fractured
rocks and breccia has broken broad zones of the massive beds of
quartzite into lozenge-shaped blocks, the longer axes of which are
parallel to the bedding and movement. These later-formed blocks have
not been re-cemented by secondary quartz, and the cracks are taken
advantage of in quarrying, the fragments being easily picked apart.
Thus the rock has been affected by at least two dynamic movements,
separated by a considerable interval of time.

The shear-zones, often several feet in width, particularly affect the
more finely-laminated layers, which are lean in quartz, while the
relief in the more massive layers has resulted in complex fracturing.
In the first phase of production of the schist, the irregular fractures
pass into rather regular fractures, cutting the beds nearly at right
angles. As the action becomes more intense in the more argillaceous
beds, the angle of fracture, or cleavage, as it may now fairly be
called, becomes more acute, and in the most intense phase this cleaved
rock passes into a well-developed schist, the foliation of which is
parallel to the bedding. The phenomena of shearing are here therefore
very similar to those at Devil’s Lake, except that the process has gone
farther.

When studied in thin section, the massive beds of quartzite show more
decided effects of dynamic action than at Devil’s Lake. However, the
major portions of the grains of quartz have distinct cores which are
often beautifully enlarged. In some cases nearly every grain has thus
grown, perfectly indurating the rock. But, also, nearly every grain of
quartz has a wavy extinction, and many of them have been fractured,
as mentioned of a few of the quartz grains of the quartzites of the
south range. In one case the pressure has been so great as to produce
rather numerous roughly parallel lines of fracture. It is thus seen
that the dynamic effects are not confined to the schist zones, but
are also prominent within the heavy beds of quartzite. This was to
be expected; for while the major part of the accommodation necessary
to bend the rock mass as a whole took place along the shear zones,
the accommodation required to bend each of the rigid heavy beds of
quartzite must have taken place within each layer. To the consequent
intense pressure and the rubbing of the grains over one another, are
wholly attributed their wavy extinction and fractures.

In the schists of the shear zones, as at the south range, the thin
sections show that the original quartz grains were small; interstitial
material was present, and mica has developed more largely than in the
quartzite. However, in the most crystalline phases, the fragmental
cores of the quartz grains and their frequent enlargements are plainly
seen. Thus the shearing has not been sufficient to produce a completely
crystalline schist, although this would not be macroscopically
discovered, unless it were suspected because the rock is not thinly
foliated.

As the dip of the quartzite is so steep at this locality, it is
difficult to say how far the shifting of the beds over one another
lessens the apparent thickness. The shear zones as well as the friction
conglomerates appear to be parallel to the bedding. If they are exactly
so, this shearing action would necessitate an estimate of the original
thickness greater than now shown, since the shear zones probably have
less width at the present time than the beds from which they were
originally produced.

Cutting the bedding are heavy joints inclined to the north at an angle
of 20° to 30°. If slipping had occurred along these in the right
direction, this might cause a small thickness of beds to have a great
apparent thickness. However, the schists above described weather out
on the face of the cliffs, and are therefore marked by recessions in
the walls. If slipping parallel to the jointing had occurred since the
schists were formed, these depressions ought not to match on opposite
sides of the joints; but, on the contrary, they continue unbroken from
foot to top, and probably the joints were formed simultaneously with or
later than the belts of schist. Consequently, at the upper narrows of
the Baraboo no evidence was found of faulting which could reduce the
estimated thickness of the quartzite as given by Irving.

As Irving clearly saw, bearing strongly in favor of the theory of a
great fold, is the increasing steeper dip of the layers in passing
north. The phenomena of movement and metamorphism corresponding so
exactly to those required by a simple fold, the question may be asked
if these are not evidence of some weight in favor of the general
correctness of Irving’s conclusion as to the structure. Had monoclinal
faulting extensively occurred, it would not have been necessary to have
had so great a readjustment of the beds as has been shown to occur by
the schists, cleavage, and the exceedingly intricate macro-fracturing
and micro-fracturing of the rock beds and their constituent particles.

In addition to the phenomena described by Irving, in summary, the
Baraboo quartzite ranges show results of dynamic metamorphism as
follows: A fine example of the Reibungs Breccia may be seen. A fault
zone of limited throw exists. All phases are exhibited, between a
massive quartzite, showing macroscopically little evidence of interior
movement through a rock exhibiting in turn fracture and cleavage, to
a rock which macroscopically is apparently a crystalline schist. The
foliation of the schists is parallel to the original stratification,
being consequent upon the movements of the beds over one another,
readjustments occurring mainly in the softer layers. In thin sections
the schists still give clear evidence of their fragmental origin,
but also show the mechanical effects of interior movement. These
same effects are apparent within the heavy beds of quartzite, some
readjustment of the particles to their new positions being here also
necessary. There is no evidence that the semi-crystalline character
of the schist and quartzite are due to high heat. Nowhere are the
particles fused. So far as they are destroyed it is by fracture, and
the rock is again healed by cementation.

The rock, in its most altered condition being a semi-crystalline
schist, and in other parts showing less change, can be connected with
its original state. Had the folding been more intense, it is reasonable
to suppose that the entire rock would have been transformed into a
completely crystalline quartz-schist, showing no evidence of clastic
origin, and possibly the foliation throughout would have corresponded
to the original bedding.

                    C. R. VAN HISE.


FOOTNOTES

    [8] The Baraboo Quartzite Ranges, by R. D. Irving. In Vol. II,
        Geol. of Wis., pp. 504–519.

    [9] The Classification of the Early Cambrian and pre-Cambrian
        Formations, R. D. Irving. In 7th Annual Rep., U. S. G. S., pp.
        403–408.

   [10] Enlargement of Quartz Fragments and Genesis of Quartzites, by
        R. D. Irving and C. R. Van Hise. In Bull. 8, U. S. G. S., pp.
        33, 34.

   [11] The Baraboo Quartzite Ranges, by R. D. Irving. In Vol. II,
        Geol. of Wis., pp. 510, 516.

   [12] The Baraboo Quartzite Ranges, by R. D. Irving. In Vol. II.,
        Geol. of Wis., p. 516.




THE CHEMICAL RELATION OF IRON AND MANGANESE IN SEDIMENTARY ROCKS.


Iron and manganese are frequent constituents of sedimentary rocks,
in some places occurring finely disseminated through sandstones and
shales, or forming a part of limestones, in other places forming
the mass of the deposit in which they occur. They are both derived
primarily from similar, and often from the same sources, and are in
many respects alike in their chemical behavior in nature. For these
reasons it is to be expected that they would frequently, if not
generally, be deposited in intimate association. Such is found to be
the case, and iron and manganese are often closely associated in the
same deposits. Very often, however, iron and manganese deposits occur
close together, but distinctly separated, while sometimes extensive
deposits of iron, and less commonly of manganese, occur with little or
almost no association with each other.

It is the object of the present paper to discuss the agencies which
are instrumental in causing these substances to be deposited sometimes
together and at other times separately. The subject is of interest as
showing how slight differences in the chemical behavior of their salts
may cause the almost complete separation of metals once intimately
associated.


THE CONNECTION OF IRON AND MANGANESE IN NATURE.

A few words concerning the relation of manganese to iron in nature
will perhaps make the following discussion clearer. One of the most
common modes of occurrence of manganese is with iron, though extensive
deposits containing manganese more or less free from iron often
occur. When associated with iron, manganese occurs with it in various
ways. Sometimes the two are intimately mixed, so that they have the
appearance of a homogeneous mass, resembling iron ore when iron is
in the preponderance and manganese ore when manganese predominates.
In such cases there appears to be no tendency to combine in one fixed
proportion, though, as iron is a much more abundant substance than
manganese, the mixture most commonly contains an excess of iron, and
exists in the form of a manganiferous iron ore. The manganese, when
not intimately mixed with the iron, may occur in it in pockets or as
scattered nodules and concretions. Such occurrences as those described
are frequent in the Lake Superior iron region, the Appalachian Valley
of the eastern states, in Nova Scotia, Arkansas, Colorado, New Mexico
and innumerable other places. In Virginia very common occurrences are
alternating layers of iron and manganese ore. The iron in such cases is
generally in the larger quantities and the more continuous deposits;
while the manganese is often represented by thin lenticular layers or
by bands of nodules.

From such cases, where iron predominates, there are all gradations
in admixture, up to the rarer cases where manganese predominates.
Frequently a given geologic horizon is characterized by both iron and
manganese, though in one case it may contain only iron, in another
only manganese, and in still another iron and manganese mixed in
various proportions. A remarkable case of this is seen in the iron
and manganese horizons immediately above, or a short distance above,
the Paleozoic quartzite, on the east side of the Appalachian Valley,
especially in the Valley of Virginia.[13] Here deposits of iron
ore, of manganese ore, and of both ores mixed, are found at various
points along the same geologic horizons. Similar alternations also
occur in the Lower Silurian novaculites of the Ouachita Mountains of
Arkansas,[14] in Cebolla Valley, in Gunnison county, Colorado,[15] and
in many other places. In many cases certain horizons are characterized
over large areas by iron alone, and but little manganese, as is well
seen in the Clinton formation and in the Tertiary iron-ore horizons of
Arkansas and Texas; while, on the other hand, some areas of certain
horizons contain considerable quantities of manganese and very little
iron, as is seen in parts of the Marine limestone in New Brunswick and
Nova Scotia, and also in parts of the metamorphosed Cretaceous shales
of California.


THE SOURCE OF IRON AND MANGANESE IN SEDIMENTARY ROCKS.

The iron and manganese contained in sedimentary strata may be
considered as derived primarily from the decay of pre-existing rocks.
Some of the later sedimentary rocks may have derived a part or all of
their iron from older sedimentary rocks, which, in turn, had derived
their iron and manganese from still older rocks. In this way the iron
and manganese in a given geologic horizon may have formed a part of
various older horizons before they reached their present resting place,
but, in every case, their primary source can be traced back to the
original materials from which sedimentary rocks were first formed.
In certain cases the sea water has supplied a certain amount of iron
and manganese to sedimentary rocks, but in such cases the sea water
acts only as a carrier of these materials from the land areas or from
submarine sources to the strata then forming.


THE TRANSPORTATION OF IRON AND MANGANESE IN NATURE.

The process that goes on in this interchange of iron and manganese from
older to younger rocks is as follows:

(1) The conversion, by surface agencies, of the minerals containing
iron and manganese into forms that can be taken into solution by
surface waters.

(2) The solution of the iron and manganese in surface waters,
acidulated with organic and sometimes inorganic acids, and their
transportation in this form from the areas of older rocks to areas over
which younger rocks are being deposited.

(3) Finally, the precipitation in one or more of several ways of the
iron and manganese contained in solution.

The iron and manganese thus chemically precipitated may be deposited
either with mechanical sediments, such as sand, clay etc., or without
them. If the deposition of mechanical sediments is largely in excess
of the precipitation of iron and manganese, the final products will be
beds of ferruginous shale, sandstone, etc., common in many geologic
horizons. If the precipitation of iron and manganese is in excess of
the deposition of mechanical sediments, the resulting products are
deposits of more or less pure iron and manganese ore. Between these
two extremes there are all gradations in the admixture of the iron and
manganese with mechanical sediments.

Frequently the iron and manganese which were originally finely
disseminated through shale, sandstone, etc., are subsequently
concentrated into bodies of comparatively pure ore, and very commonly
this concentration takes place by a process of re-solution of the iron
and manganese and re-deposition by replacement with limestone, or,
more rarely, with some other material. The limestone or other material
which thus acts as a precipitant is often in the same series of strata
from which the iron and manganese were removed, and thus these two
substances, which were once in a finely disseminated condition, may be
converted into deposits of comparatively pure ore and yet remain in the
same general series of strata in which they were originally deposited.
A remarkable case of this is seen in the iron deposits of the Penokee
series in Michigan and Wisconsin,[16] to be mentioned again on page
370. It has also been suggested by H. D. Rogers[17] that certain
siderite deposits in the Coal Measures were formed by the conversion
of finely disseminated sesquioxide of iron into carbonate of iron by
organic matter, and the subsequent segregation of the carbonate as now
found in layers and nodules.

The surface waters that carry the iron and manganese to the strata
being deposited at a given time are sometimes derived from areas
in which iron predominates, sometimes from areas in which iron and
manganese are both abundant, and sometimes, though rarely, on account
of the scarcity of such regions, from areas in which manganese
largely predominates over iron. If iron and manganese were always
precipitated from these waters in similar chemical forms and under
the same conditions, it would be expected that the strata deriving
their iron and manganese from surface waters would contain those
substances in the same relative proportions as they had existed in
the rocks from which they were derived, and that they would be in an
intimately mixed condition. Such is doubtless often the case, or at
least approximately so; but it is also often the case that iron and
manganese occur in separate deposits, yet in close proximity to each
other and often alternating along the same horizon. Besides this, the
two substances frequently form parts of the same deposit and yet are
distinctly separate from each other. In such cases the question arises
as to why the iron and manganese are not intimately mixed in the form
of a manganiferous iron ore, as would be expected if they had been
precipitated together. Moreover, deposits sometimes occur which are
composed largely of manganese ore, with little or almost no iron, and
when the source of the manganese is looked for, we often find that the
rocks which probably supplied it contained both manganese and iron, and
that the iron was present in a much larger proportion as regards the
manganese than in the new deposit. Here again the question arises as to
why the iron and manganese are not in the same relative proportions in
the new deposit as they were in the rocks from which they were derived.

Four principal causes suggest themselves in explanation of this
separation:

(1) It might be supposed that the deposits containing mostly iron and
those containing mostly manganese received these constituents from
waters derived from different sources, and carrying iron and manganese
only in the proportions in which they deposited them. Under some
conditions this explanation might suffice, but in many cases, such as
when iron and manganese alternate along the same geologic horizon, and
yet in close proximity with each other, the explanation is entirely
inadequate, for the deposits are too close to each other to have been
formed from different supplies of surface waters.

(2) It might be supposed that the iron or the manganese had been
leached out of a deposit of the mixed ores, leaving one free from
the other and depositing the dissolved ore somewhere else. This
explanation, except in special cases, also appears inadequate, because
the reagents in surface waters, which dissolve iron and manganese, seem
to affect both about equally, so that if one were dissolved, the other
should be taken up in the same way. Doubtless small differences could
be found in the behavior of the organic and inorganic compounds in
surface waters towards iron and manganese minerals, but they would be
small as compared with the more active reactions which go on.

(3) It might be supposed that a separation could be produced by
secondary concentration such as segregation, replacement, etc. This
has doubtless sometimes been the case, but where the concentrating
action is not assisted by a difference in the chemical behavior of the
two substances, the separation would only be on a small scale. Even
in the case of concentration by replacement of limestone, if iron and
manganese both acted in the same way during the replacement, it would
be expected to find them deposited in an intimate mixture. Though this
secondary concentration, therefore, unassisted by other agencies, would
not produce all the results found in nature, yet, when it is thus
assisted, it often plays an important part.

(4) The fourth, and what seems the most important, factor in the
separation of iron and manganese, is that, though very often they are
precipitated in the same form from the same solution, yet sometimes
they are precipitated in different forms; and even when precipitated in
the same form, the precipitation of one sometimes requires different
conditions from the precipitation of the other. This fact will explain
the alternate association and separation of iron and manganese, not
only when no secondary concentration has gone on, but also in cases
where such concentration has taken place, such as in the replacement
of limestone, etc.

It will now be attempted to show how the various degrees of association
and separation of iron and manganese found in nature may be produced by
different conditions during deposition.


THE FORMS OF IRON AND MANGANESE DEPOSITED AT ORDINARY TEMPERATURES.

The mineralogical forms in which iron and manganese are deposited from
solution in nature at ordinary temperatures depend on the conditions
of air and water, whether of an oxidizing or a reducing nature, and on
the character of the associated organic and inorganic matter either
in solution or on the floor of the sea, lagoon or bog in which the
deposition occurs.[18] There are four principal methods by which iron
and manganese are precipitated in nature from surface waters:

(1) By oxidation, as in the case of the precipitation of hydrous oxides
and in the precipitation of the carbonate by the partial oxidation of
more complex organic salts.[19]

(2) By reduction, as in the precipitation of sulphide of iron by the
reduction of sulphate of iron.

(3) By gaseous or soluble precipitants, as in the precipitation of
sulphide of iron by the action of sulphuretted hydrogen or a soluble
sulphide on a soluble salt of iron, and as in other cases to be
mentioned later.

(4) By replacement of carbonate of lime or some other substance.
Different forms are precipitated by these different methods.

Iron at ordinary temperatures is usually deposited from solution as
the hydrous sesquioxide, the carbonate, the sulphide or the hydrous
silicate of iron and potash known as glauconite. Manganese under
similar conditions is deposited as the hydrous oxide[20] or as the
carbonate, and possibly sometimes, though very rarely, as sulphide.

When solutions of organic or inorganic salts of iron and manganese are
freely exposed to the action of air, as in shallow or rapidly moving
streams, or in lakes and some bogs, they are quickly oxidized and
both may be deposited as more or less hydrous oxides. In many bogs,
however, the metals may be precipitated as hydrous oxide on the surface
where oxidizing agencies predominate, but when these oxides sink and
come into contact with decaying organic matter, free from the active
oxidizing influences of the air, they may be reduced to carbonates.

The carbonates of iron and manganese may be precipitated when the
solutions containing them are protected from oxidation by a reducing
agent, such as decaying organic matter, or by being far removed from
the air. Carbonate of manganese, however, is a much more stable
compound than carbonate of iron, and the oxidizing conditions are
often sufficiently strong to cause the deposition of iron as hydrous
sesquioxide and not strong enough to change the manganese from its
carbonate form. It is not uncommon, therefore, to have iron deposited
in one place as hydrous sesquioxide, and manganese carried further on
and deposited as carbonate, or even under special conditions deposited
as carbonate with the hydrous sesquioxide of iron. Fresenius[21] has
shown that the warm springs of Wiesbaden, which contain iron and
manganese among their other mineral constituents, deposit iron in the
form of hydrous sesquioxide, while manganese is carried on further
in solution and deposited as carbonate. In this behavior, therefore,
we have the first striking difference in the deposition of iron and
manganese, and it will be further discussed later on.

The sulphides of iron and manganese differ very much in their nature
and mode of occurrence. Iron is frequently deposited as sulphide, but
manganese rarely occurs in that form, and when it does it is always in
very small quantities. Iron forms several sulphides in nature: pyrite
(FeS₂), marcasite (FeS₂),[22] pyrrhotite (Fe₁₁S₁₂), troilite (FeS) and
numerous other more complex compounds unnecessary to enumerate here.
Pyrite is the commonest form of iron sulphide, and occurs in rocks of
all ages, from Archean to Recent. It is formed in nature by the action
of soluble sulphides or sulphuretted hydrogen on soluble salts of iron,
and also by the reduction of sulphate of iron by organic matter or
other reducing agents. Manganese forms two[23] sulphides, alabandite
(MnS) and hauerite (MnS₂). Both minerals are very rare, and so unstable
that they rapidly oxidize on exposure. Alabandite is the less rare
form, and usually occurs as a subordinate constituent of certain
metalliferous veins or allied deposits.

Though the sulphides of manganese are easily oxidized, they are
not so unstable that, had they ever been formed in considerable
quantities in sedimentary deposits, they would, even at considerable
depths, have left no trace of their former presence. Moreover, the
sulphide of manganese, as produced artificially,[24] is soluble in
certain organic acids, notably acetic, and, as the conditions for the
deposition of sulphides of metals in sedimentary deposits generally
require the presence of organic matter, it is not improbable that some
of the acids given off by such matter would be capable of dissolving
sulphide of manganese. Here, then, is one reason why manganese might
not be deposited as sulphide under some conditions which would cause
the precipitation of sulphide of iron. Moreover, the artificial
formation of sulphide of manganese (alabandite) in the laboratory is
brought about most easily at high temperatures. It has also been
noted that when manganese, in the form of the alloys spiegeleisen and
ferro-manganese, is added to molten steel, it bodily removes a part of
the sulphur; and it is thought by some metallurgists, that sulphide of
manganese is formed and carried into the slag.

These and other indications of the more easy transition of manganese
into the form of sulphide at high rather than at low temperatures
afford another cause which might prevent sulphide of manganese from
being formed in sedimentary deposits, for such deposits are usually
laid down at ordinary temperatures. On the other hand, they also
afford a cause which might lead to the deposition of the sulphide of
manganese in certain metalliferous veins and other deposits, where the
temperature at the time of deposition may have been high.

In many of the silver and lead deposits of the Rocky Mountains
manganese oxides occur with the superficial oxidation products of the
sulphides of other metals, and it has often been suggested that the
manganese also was originally in the form of sulphide. This may be true
in some cases, for alabandite has been found in a few metalliferous
deposits in Colorado, Mexico, Germany, Peru and elsewhere, but in most
cases, at least in the Rocky Mountains, when the level is reached at
which the oxidized forms of lead, zinc, iron and other metals pass into
sulphides, the manganese passes into carbonate or silicate, and remains
in one or both of those forms to all depths that have been reached.

In the deposition of iron and manganese as sulphide, therefore, there
is a most marked difference of behavior, and here again is a good cause
for the separation of the two substances in sedimentary rocks, as will
be more fully explained below.

Iron is often deposited in sedimentary formations as the hydrous
silicate of iron and potash known as glauconite, and composes the
mass of the large greensand beds common in Cretaceous and Tertiary
strata; but manganese is not found in an exactly similar condition.[25]
Here again, therefore, is an important difference in the modes of
deposition of iron and manganese, which also will be mentioned again.

It will thus be seen that while some of the forms in which iron and
manganese are deposited are the same, others differ very widely, and
even similar forms are often deposited under different conditions.
It is doubtless to these various forms and conditions of deposition
that the alternate association and separation of iron and manganese in
nature are due.


CAUSES OF THE ASSOCIATION OF IRON AND MANGANESE.

The very frequent intimate association of iron and manganese in
sedimentary rocks is what would be expected from a deposition as oxide
or carbonate in basins such as coastal lagoons or bogs, where the
waters moved very slowly, or not at all, for under such conditions,
they are often deposited together.[26] Moreover, it is a well-known
fact that isomorphous substances have a strong tendency to combine in a
homogeneous mass, and to crystallize together in different proportions.
Carbonate of iron and of manganese are isomorphous with each other,
and this is hence a possible cause of the frequent intimacy of their
association, such as is seen in almost all manganiferous spathic iron
ores, whether these ores are formed by direct precipitation or by
replacement of carbonate of lime. The oxidation of such a mixture would
give the common form of an intimately combined iron and manganese ore.

Since there is usually more iron than manganese in the rocks from which
both metals were originally derived, the surface waters draining from
areas of such rocks usually contain the metals in a similar proportion.
Hence, in cases where the deposition of the carbonates of both occurs
at the same spot, the isomorphous carbonates derived from the solutions
have a larger percentage of carbonate of iron than of carbonate of
manganese, and the resulting oxides contain the two metals in the same
proportion, thus giving rise to the common low-manganese iron ores.

The hydrous oxides of iron and manganese, however, are not
isomorphous,[27] and, therefore, when they are precipitated together,
as in bog-deposits, the association is often much less intimate than
in the cases just mentioned, and is simply due to the fact that, under
certain conditions, the oxides of both metals are precipitated in the
same place.


CAUSES OF THE SEPARATION OF IRON AND MANGANESE.

When iron and manganese ores occur in more or less separate deposits,
it becomes necessary to suppose the action of influences different from
those which cause the deposition of both together, and such influences
are to be found in the different modes of precipitation, under certain
conditions, of the two metals. It has been shown by Fresenius[28] that
certain warm springs, on reaching the surface, first deposit hydrous
sesquioxide of iron, and farther on carbonate of manganese. This not
only points to the well-known fact that carbonate of iron is more
easily oxidized than carbonate of manganese, but it also leads to the
belief that the bicarbonate or other salt of iron in the water is more
easily oxidized than the manganese salt.

An action somewhat similar to that described by Fresenius readily
explains the occurrence of manganese sometimes in entirely separate
deposits, sometimes in distinct but closely alternating deposits.[29]
Under certain conditions, if the waters from which the precipitation
took place were moving, the iron and manganese, owing to the difference
in oxidability, as stated above, would be laid down in different
places, resulting in the formation of deposits of iron ore free from
manganese, and manganese ore free from iron in different positions
along the plane of the same geologic horizon. Such occurrences are
often seen in the iron regions of the Appalachian Valley, where there
are often found, in different places along the same belt, deposits
of iron ore and deposits of manganese ore in positions similar with
relation to the enclosing rocks.

These conditions of moving water might also cause the occurrence of
the two ores in interstratified layers, as is sometimes the case. Such
a condition would result if iron were deposited in a certain place at
one time, and if, later, on account of some increased facility for
oxidation, iron was deposited before it reached that place, and the
manganese, being less easily precipitated, were carried on and laid
down upon the first deposit of iron.

Suppose the metalliferous solutions to be confined in a shallow
basin, or, at least, to pass through it so slowly that they become
thoroughly oxidized. Under such conditions the deposition of iron and
manganese would go on continuously, and so nearly on the same spot that
a comparatively homogeneous manganiferous iron ore would be formed.
If the supply of metalliferous solutions were not continuous, but
were intermittent, as is sometimes the case in local basins, such as
coastal lagoons, which are often dependent for their supply of water
on the changes of season and the sudden fluctuations of weather, then
interstratified layers of iron and manganese ore might be produced. The
iron, becoming oxidized on the surface, sinks to the bottom, possibly
in some cases to be converted there to the simple carbonate by organic
matter. Further oxidation precipitates hydrous oxide or carbonate of
manganese on top of the iron. A renewed supply of surface waters brings
more solutions of iron and manganese, or else the evaporation of the
water in the closed basin concentrates the materials which have not
yet been precipitated. In either case there is a further alternate
deposition of the two ores.[30]

Another process of separation of iron and manganese in nature might
take place by the formation of sulphide of iron. It has already been
shown that iron is sometimes deposited as sulphide and later oxidized
in the same manner as the carbonate. Manganese, on the other hand,
is rarely found as sulphide, and there is reason to think that the
sulphide never represented the original form of any large sedimentary
deposits of manganese ore (see pages 364 to 365). It seems probable,
therefore, that from a solution of iron and manganese in surface waters
the iron might, where the conditions are favorable, be precipitated
as sulphide (FeS₂) and the manganese might be carried on in solution
to be deposited somewhere else as oxide or carbonate. Subsequently
the oxidation of the ores would give rise to oxide of iron from the
sulphide and oxide of manganese from the carbonate; and the two ores,
though occurring at the same horizon, would be separated by a greater
or less distance.

After the deposition of the sulphide of iron, the conditions might
change and permit the deposition, in the same place, of the carbonates
of iron and manganese together. This is an easy case to imagine, and
where such a deposit was exposed to surface influences, the resulting
product would be oxide of iron from the underlying sulphide and a
manganiferous iron oxide from the overlying isomorphous carbonates.
Hence another possible cause of the frequent association of pure iron
ores and manganiferous iron ores. It is possible also that after the
solution of iron and manganese had been freed from the former by
precipitation as sulphide, the manganese might be carried on and laid
down as carbonate on a previous deposit of iron sulphide, and when such
a combination was oxidized, the result would be oxide of iron and oxide
of manganese in beds closely associated but yet distinct.

By supposing the iron sometimes to be deposited in sea water as
glauconite, a manner in which manganese is not laid down (see page
365), a further means of separation of the two metals would result.

Thus by alternating the conditions of the deposition of iron and
manganese in different forms, a great variety of methods of association
and separation of the two metals can be produced.

The above discussion refers not only to the deposits of iron and
manganese ores of notable size, but also to the iron and manganese
frequently found disseminated through shales, sandstones etc. In these
rocks they usually form a small but often a very important part, for in
many cases the iron and manganese is taken into solution from the rocks
and redeposited by a process of replacement with carbonate of lime
in neighboring beds of limestone, or more rarely by replacement with
other rocks, thus giving rise to important ore deposits. The question
of the association and separation of the iron and manganese in these
replacement deposits depends on a number of conditions, the principal
of which are, just as in the class of deposits that has been discussed,
the conditions during deposition and the forms in which the iron and
manganese are precipitated. The processes by which association and
separation occur in replacement deposits differ somewhat in detail from
the processes just discussed, but are based on the same principles.

Many of the iron and manganese deposits of the Appalachian region are
supposed by many to be replacement deposits. N. S. Shaler[31] in 1877
suggested that some of the iron deposits of Kentucky and Ohio were
formed by the solution of iron from certain rocks, and its deposition
in the form of carbonates by replacement with underlying limestone.
Subsequently it was changed by oxidation to brown hematite. A notable
case of replacement has also been shown by R. D. Irving and C. R. Van
Hise[32] in the iron deposits of the Penokee series of Michigan and
Wisconsin. Here the ore is supposed to be partly a replacement of chert
in a trough between quartzite and igneous rocks. The solution that
contained the iron was derived from strata in the same series of rocks
in which the iron was re-deposited and contained a certain amount of
manganese. It is shown how the iron and manganese were more or less
separated in the replacement process and that the separation was due
to the difference in the oxidability of the carbonates as explained on
page 363.

                    R. A. F. PENROSE, JR.


FOOTNOTES

   [13] The exact age of the iron and manganese deposits here referred
        to is, in some cases, a little uncertain. Some may be Cambrian,
        others Silurian, but the exact determination of the age of the
        horizon is not a part of the present discussion. The matter has
        been discussed by the writer in Geological Survey of Arkansas,
        1890, Vol. I., pp. 376–379.

   [14] See Geological Survey of Arkansas, 1890, Vol. I., pp. 320–325.

   [15] See Geological Survey of Arkansas, 1890, Vol. I., pp. 456–457.

   [16] R. D. Irving and C. R. Van Hise, U. S. Geol. Survey, Tenth Ann.
        Report, 1888–1889, Vol. I, pp. 409–422.

   [17] Geol. Survey of Penn., Vol. II, 1858, p. 739.

   [18] The solutions may be precipitated, as already shown, either
        with or without admixture with mechanical sediments; and there
        are in nature all gradations from almost pure deposits of iron
        and manganese ore to beds of shale, sandstone, etc. stained
        with iron or manganese. Subsequent concentration frequently
        causes decided changes in the latter deposits (see p. 370).

   [19] It has been suggested by A. A. Julien (Proceed. Amer. Assoc.
        Adv. Sci., Vol. XXVIII., 1879, p. 356) that in some cases the
        carbonates of iron and manganese may be only the fixed residue
        of organic compounds of more complex form once in solution in
        surface waters.

   [20] This oxide is generally in the form of the peroxide or the
        sesquioxide in a more or less hydrous condition.

   [21] Jahrb. des Vereins f. Naturkunde in Herz. Nassau, Vol. VI., p.
        160 (Bischof).

   [22] Marcasite has the same composition as pyrite, but differs in
        crystalline form.

   [23] Manganese also occurs in the mineral youngite, which contains
        lead, zinc, iron, manganese and sulphur, but the mineral is
        considered of doubtful homogeneity. (See System of Mineralogy,
        E. S. Dana, 1892).

   [24] When manganese is precipitated artificially as sulphide it is
        usually in the form of the monosulphide (MnS), in either a
        hydrous or an anhydrous form.

   [25] Manganese occurs in various hydro-silicates, but they do not
        appear to be deposited as sedimentary strata in the same manner
        as glauconite.

   [26] If the water moved very slowly, the deposition would probably
        take place approximately in the same spot; if the waters moved
        more rapidly, the iron might be deposited in one place and the
        carbonate in another, in the way explained on page 363.

   [27] The hydrous oxides of iron are not crystalline.

   [28] See p. 363.

   [29] Bischof suggests that the action described by Fresenius causes
        the separate deposition of iron and manganese; and also that it
        explains the occurrence of large deposits of manganese ore in
        regions where the iron ore contains least of that ingredient.
        (See Elements of Chemistry and Phys. Geol., Vol. III., pp.
        531–532.)

   [30] In some cases these iron and manganese deposits are undoubtedly
        formed by the replacement of limestone or other rocks, as is
        further discussed on pages -- to --.

   [31] Kentucky Geol. Survey, Report of Progress, Vol. III., New
        Series, 1877, p. 164.

   [32] U. S. Geol. Survey, Tenth Annual Report, 1888–1889, Vol. I.,
        pp. 409–422.




SOME RIVERS OF CONNECTICUT.[33]

  _Outline._--Introduction.--Topography of Connecticut: The upland
      plateau, its origin, date, elevation, valleys sunk beneath its
      surface.--Lowland on the Triassic area.--Later oscillations.--
      Résumé of the topography.--Early drainage.--Re-adjusted streams.
      --Revived streams.--Unconformable rivers, consequent or
      superimposed.--Pleistocene changes; the Farmington, Quinnipiac,
      Scantic.--Abandoned gaps.


_Introduction._ In order to study intelligently the history of a river,
one must first become acquainted with the present physical geography
of the region in which the river lies, and know the stages of its
development. Therefore, before classifying the rivers of Connecticut,
I shall consider the topography of the state, and in a few paragraphs
outline the successive cycles in the history of its growth. The scope
of this article will not permit a discussion or even a full statement
of the evidence on which these conclusions are based. They have been
stated at considerable length by Professor W. M. Davis,[34] and the
reader is referred to his papers for the complete discussion. His
conclusions in respect to the physical geography are accepted here
without question, and form the basis for the discussion on the rivers
of the state.

[Illustration: FIG 2]

_Topography of Connecticut._ Connecticut can be said to consist of two
great areas quite distinct in topography and geologic structure.[35] On
the east and on the west are the crystalline uplands which rise from
sea level along the Sound to 1,700 and 1,800 feet in the northwestern
part of the state, and to 600 and 700 feet in the northeastern.
These uplands consist chiefly of gneiss and granite, probably of
pre-Paleozoic age, which are now much folded, faulted and crumpled.
Between these two areas of crystallines is a lowland belt of Triassic
sandstone and shale, twenty to twenty-five miles wide, extending from
New Haven north through the center of the state and including in its
borders New Haven, Meriden, Hartford, New Britain and many towns of
lesser note. These sandstones form a monocline with an eastward dip
of 10° to 30°, and in addition to being tilted they have been faulted
since their deposition in a shallow, slowly-subsiding trough of
crystallines. Their thickness is variously estimated--3,000 to 5,000
feet, Dana; 10,000 or more, Davis. This lowland is interrupted by a
series of trap ridges, which in general present steep faces toward the
west, whereas their eastward slope is gradual, less than the dip of the
sandstones.

_The upland plateau._ Suppose we ascend the highest point of these trap
ridges, the old tower on Talcott Mt., nine miles west of Hartford; we
are 900 feet above the sea level and more than 600 above the plain at
our feet. A few miles to the west across the sandstone valley, rise the
crystalline uplands, which extend far to the north and to the south.
On the east across the Connecticut we see the eastern uplands. The
first impression, which comes to one as he gazes upon these uplands
and which is strengthened with each view, is that few hills rise above
the general level of the plateau; the crest line is nearly horizontal,
declining gently to Long Island Sound. Above this general level are
a few rounded domes, but no sharp, towering peaks. Below it valleys
have been cut, but they do not destroy the plateau-like appearance. A
view from the western plateau across the sandstone valley shows the
remarkably even crest line of the trap ridges, a crest line which
approximates in height the uplands on the east and west. A nearer view
of the upland corroborates our first impressions of the gently rolling
character of the inter-stream surfaces, but we have a better view of
the valleys which have been sunk beneath the general level and of the
low rounded hills which rise above it. In popular parlance the country
is “hilly.” It is uneven, not because there are high hills, but rather
because there are deep valleys. If in imagination we fill up these
valleys and the wide Triassic lowland to the general level of the broad
inter-stream surfaces, we shall have constructed a gently undulating
plateau, dipping to the south and east--a peneplain.[36]

_Origin of the peneplain._ This is not a constructional surface,
for the rocks are greatly tilted, folded and faulted, so that the
surface consequent upon such disturbance must have been complex and
mountainous. Long subaërial denudation upon a folded and faulted
mass when the land stood much lower than at present produced this
plateau. Evidently it could be produced by denudation only at or near
baselevel, for the effect of erosion upon a mass high above baselevel
is to accentuate its topographic relief, not to reduce it. We naturally
ask ourselves, “At what stage in geologic history did this denudation
occur?”

_Date of the peneplain._ The erosion which accomplished this great
work must have commenced after the formation and dislocation of the
Triassic beds, for the even crest line of the trap ridges, a part of
which--perhaps all--were contemporaneous with the sandstones, is a part
of the dissected peneplain; but to fix the date of the completion of
the peneplain, we must turn to evidence presented in New Jersey.[37]
There we learn that by the close of Cretaceous times, the country was
eroded nearly to baselevel, and we may therefore speak of the relative
position of the land and sea, to which the land was at this time
reduced, as the Cretaceous baselevel, and this land surface as the
Cretaceous peneplain.

_Elevation of the peneplain._ In post-Cretaceous, presumably early
Tertiary[38] times, the land was elevated to nearly its present height
and remained at that altitude, so far as topographic evidence shows,
during Tertiary times. The proofs of this elevation are the valleys
which the streams have sunk below the general level. That this was
not a simple uplift, but was accompanied with tilting and warping, is
clear from the following considerations. The depth to which a stream
can cut its valley depends directly upon its height above baselevel.
If the present surface were a peneplain uniformly elevated, the head
waters and middle courses of a river would not be cut so deep in the
surrounding plain as its lower course. But the reverse is true of the
rivers of Connecticut. The depth of the valley increases inland, being
greater in those regions where the peneplain was raised the highest. A
comparison of the upper and lower valleys of the Housatonic, Naugatuck,
Quinnebaug, and of the Connecticut at Middletown, where it enters the
plateau, and at its mouth, will give some idea of the amount of the
warping. It will not give an _exact measure_ of it for several reasons:
first, the upper courses of the rivers have not yet reached the present
baselevel; second, the present altitude of the uplands is the result
of the post-Cretaceous uplift and warping, plus a probable later
post-Tertiary uplift (to be mentioned later), besides several minor
oscillations, the last of which was downward, and is recorded near the
coast in the drowned condition of the rivers. As has been already said,
the peneplain is highest in the northwest, and gradually declines to
sea level toward the south and east.

_Consequences of the uplift._ The consequences of this uplift are
seen in the valleys, which are cut into the peneplain, and which have
destroyed the level character of the country. In the hard crystalline
rocks the valleys are generally narrow and deep, with bold slopes;[39]
where they are cut in the crystalline limestone, they are wider and
more open. In marked contrast, however, is the lowland on the Triassic
area in which only the trap ridges remain to tell of the former
altitude of the general surface, and the immense amount of erosion
which has taken place on the soft sandstones and shales. Indeed erosion
has progressed so rapidly on these soft rocks, that they have been worn
down almost to a new baselevel in the same length of time in which the
hard crystallines have been only trenched. This fact cannot be too
strongly emphasized. The broad sandstone lowland from New Haven north
into Massachusetts has been carved out of the uplifted peneplain in
soft rocks, during the same time in which the Connecticut has excavated
its gorge in the crystallines below Middletown, and the Housatonic has
opened its upland valley on the limestones. The difference in results
is due not to a difference of time, but to the difference in the
relative hardness of the rocks.

On the basis of this principle the age of certain river gorges to which
reference will be made later can be fixed. The _narrow_ passage of
the Quinnipiac through a sandstone ridge southwest of Meriden cannot
belong to the same cycle of erosion as the _broad sandstone lowland_
on either side of it, but manifestly must be much younger. So, also,
the narrow passage of the Farmington at Tariffville, where it crosses
the trap ridge through a gorge free from drift, is of much later date
than the _broader_ valley more or less encumbered with drift which the
upper part of the same river has cut in the hard crystalline schists.
Cook’s Gap in the trap sheet west of New Britain is much broader than
either of the above, and belongs to the Tertiary cycle of erosion,
although as I shall endeavor to show later, it was probably not
occupied by a stream during the whole cycle. In marked contrast, also,
with the Tariffville gorge is the gap by which the Westfield river in
Massachusetts cuts the trap ridge. This gap was formerly broad and
open--the result of Tertiary erosion--but is now filled with drift,
in which the river is at present working. Since these two rivers are
essentially the same in size, are now at the same level, and the rock
is the same in both cases, the only explanation for the difference in
the two passages is that they belong to different cycles.

To recapitulate, the results of the post-Cretaceous uplift are seen in
the valleys which have been cut in the peneplain. The narrow valleys
in the gneisses and schists, the upland valleys in the limestones, the
wide open, drift encumbered gaps in the trap ridge,--Cook’s and the
Westfield river gaps,--the broad open lowland on the sandstones, are
all the result of erosion in this cycle. The Quinnipiac gorge in the
sandstone, and the Tariffville gorge in the trap are just as surely of
a later date. They do not at all accord with the work of the earlier
cycle either in size, angle of slope, or depth.

This conclusion is somewhat at variance with an opinion expressed by
Professor J. D. Dana,[40] but it seems justifiable in view of the
successive cycles in the physical development of the region. In another
part of this article I shall consider these gaps again in connection
with their river histories, and shall give additional reasons why I
venture to differ from so eminent an authority.

_Length of this cycle._ This cycle of erosion beginning with the
post-Cretaceous uplift was not so long as the preceding cycle. In
the earlier one the whole state was reduced to a peneplain; in the
later cycle only the soft Triassic sandstones were brought near to
baselevel. It probably lasted through Tertiary times, and was brought
to a close by a slight uplift. The result of this uplift is well
shown in Pennsylvania[41] and New Jersey.[42] It is not well shown in
Connecticut, but there seem to be some traces of it in the trenches the
rivers have cut below the level of the sandstone peneplain. However,
these trenches are so much obscured by drift that a positive statement
is not warranted. It may, however, be spoken of provisionally as the
post-Tertiary uplift. There may have been later oscillations of small
amount, probably were; here and there are shreds of evidence which
point to such oscillations, but only one movement has had an effect
upon the topography, which can be recognized. The fjorded condition
of all the rivers along the Sound--the Norwalk, Saugatuck, New Haven
bay, Niantic and Thames are the best examples--shows that within
comparatively recent time there has been a slight subsidence of the
land. But this movement is not to be compared in amount with those of
the earlier cycles.

_The drift._ Over all the state in varying thickness lies the glacial
drift, either in its typical unmodified development as till, or in its
modified form, as river terraces, kames, eskers and sand-plains. It is
of importance in this connection only as it has affected the topography
of the country and so modified the drainage. Examples of these
modifications will be mentioned later.

_Résumé._ There was first a long cycle of denudation in pre-Triassic
times, during which the contorted crystallines were worn down to a
comparative level; second, a cycle of subsidence, deposition and
volcanic outburst, during which the sea entered the crystalline
trough, and the Triassic conglomerates, sandstones and shales were
deposited with the intercalated layers of lava; third, a long cycle of
elevation, folding, faulting and erosion, during which the sedimentary
beds were elevated--tilted into the present faulted monocline, and
this constructional surface worn down to a baselevel of erosion in
late Cretaceous times. Each of these cycles probably represents
the sum total of several subordinate cycles. There was, fourth, a
post-Cretaceous uplift inaugurating a period of erosion lasting
through Tertiary times and resulting in the formation of valleys in
the hardest rocks, and a lowland approaching baselevel on the Triassic
sandstones and shales; fifth, a probable late or post-Tertiary uplift,
when the valleys were deepened and the lowlands trenched--obscure in
Connecticut, but well shown farther south; sixth, the land, near the
coast at least, is now slightly lower than it has been in the not
remote past, as is shown by the fjords.

With the changes of the physical geography clearly in mind, the rivers
of Connecticut may now be examined in respect to their conditions of
origin, the number of cycles through which they have lived, and the
approach they have made to mature old age. But at the very outset a
serious difficulty is encountered, for the geological structure of
the state is nowhere well described, nor have topographic maps of
all the districts yet been issued. Since the structural details are
to some extent unknown it is unwise in many cases to attempt more
than tentative conclusions. Several of the problems to be presented
cannot be considered as settled. Considerable progress toward a
final settlement will have been made, however, if the conditions of
the problems are made clear, various hypotheses suggested, and the
attention of workers in this field called to these questions.

_Early drainage._ Of the drainage of Connecticut during Jurassic and
Cretaceous times very little can be said. It is not even known whether
it was consequent upon the Jurassic tilting and faulting, or whether
these deformations were so slow in their movement that the rivers
persisted in spite of them. It may have been that the larger rivers
were victorious, while the smaller were conquered and compelled to
assume new consequent courses. Whatever was their origin there must
have been abundant opportunities during the long erosion which resulted
in the Cretaceous baselevel, and again in the period of revived and
quickened degradation succeeding the post-Cretaceous uplift, for the
streams to adjust themselves in a large degree to the geological
structure. The contrast of hard and soft beds and the great elevation
must have been potent factors in bringing to pass such a result. We
expect to find the streams so far re-adjusted as to render improbable
the discovery of their manner of origin.

_The Housatonic, a re-adjusted stream._ The best example of
re-adjustment is found in the northwestern part of the state where the
Housatonic and some of its branches follow well adjusted courses. From
its headwaters, near Pittsfield, Mass., to New Milford, Conn., it has
nearly all the way chosen its course along the Cambrian crystalline
limestones in preference to the harder granites and gneisses on either
side. The stratigraphical relationships of the limestone are not fully
understood, but they seem to be deeply eroded anticlines and synclines,
whose axes plunge north or south at various angles. The course of
the river, if the drainage was consequent, was at first along the
synclinal valleys, passing from one to another across the lowest points
in the anticlinal ridge between them. But by a series of changes[43],
resulting from the differential rates of erosion as hard or soft beds
became exposed, the river previously to the Cretaceous baseleveling,
seems to have re-adjusted its course to the softer limestones. However,
there are several places where this conformity to structure does not
seem to be the law; where the river departs from a limestone valley to
flow for a time in the crystallines, only to return to the limestone
again. The most marked instance of this is in the towns of Sharon and
Cornwall, where the river leaves the limestone valley, which continues
to the southwest, and flows for ten miles in a narrow gorge in the
gneiss, only to again enter at its northern end a long narrow bed of
limestone. The following seems to be the probable explanation. When the
land stood at the elevation represented by the Cretaceous peneplain,
these hard beds were below or but very slightly above baselevel, and
were therefore undiscovered by the stream or had just begun to make
themselves known late in the cycle. Had they been reached early in the
cycle, when the stream was far above baselevel and presumably before
many of its tributaries had been developed, and when it was therefore a
smaller river, it is quite probable that further re-adjustments would
have occurred, and the stream been led away from the hard rocks onto
the softer beds to the west; but when they were reached the stream
had cut so deeply and so nearly to baselevel that it was safe from
capture. After the elevation of the peneplain the stream was revived
and disclosed more and more of these hard beds, but was then, owing to
the development and head-water growth of its tributaries, too important
a river to be diverted by any rival. A river of this kind may be
said to be “conformably superimposed” in distinction to one which is
superimposed from an unconformable cover.

_Revived streams._ It is important to recognize the effect of the
post-Cretaceous uplift upon the rivers at that time established. As
the land was baseleveled and the velocity of the streams decreased,
they lost in large degree their cutting power and sluggishly meandered
more or less in broad flood-plains. During and for a period after the
uplift, their cutting power was restored to them by virtue of their
increased velocity and they excavated the deep narrow valleys which we
find in the crystalline highlands. The upper course of the Housatonic
is a good example of a river re-adjusted to the structure during one
cycle, revived by uplift to a second cycle of erosion, and in places
“conformably superimposed” upon structures from which it would have
been led away in the ordinary course of re-adjustment. Its tributaries,
the East Aspetuck, Still, Shepaug, and Pomeraug follow courses
re-adjusted in one cycle and revived in a later uplift.

We can assert with the more confidence that such was the history of
the upper Housatonic, because we find in other states, in regions
whose history has been the same, similar examples of “conformably
superimposed” and “revived” streams. The Musconetcong and Pequest,
highland rivers of New Jersey, are streams “revived” from mature old
age to vigorous youth and “conformably superimposed” upon saddles of
gneiss between two limestone valleys.[44]

_Unconformable rivers._ In considering the course of the lower
Housatonic we meet with some difficulty at the outset. In the southern
part of the town of New Milford the river leaves the limestone belt
which continues with some slight interruptions to the Hudson, and
swings sharply into the crystalline plateau in a southeasterly course
until it is joined by the Naugatuck, when their united waters flow
south for a few miles to the sound. The course of the lower Connecticut
is even more surprising. At Middletown it leaves the broad open
Triassic sandstone lowland, and through a gorge enters the plateau,
which has an average elevation of 600 to 700 feet. In this plateau of
crystallines the river has sunk its valley nearly to sea-level. The
slopes are steep compared to the lines in the sandstone lowland, and
the contrast between the two parts of the river is one of the striking
features of Connecticut scenery. Several theories may be framed to
account for the curious behavior of these two rivers, but none of them
are free from all difficulty.

_As a consequent river._ The lower Connecticut has been thought[45] to
be a revived river, whose course was consequent upon the post-Triassic
tilting and faulting. The faulted monocline seems to have had the shape
of a half-boat, ends to the north and south, and one gunwale rising
toward the west, the combined effect of the tilting and faulting being
to swing the river to the southeast, where the keel of the boat was
lowest. The probable existence of faults, with upthrow on the east,
along the eastern margin of the Triassic rocks, is a difficulty in the
way of the complete acceptance of this theory. Unfortunately too little
is known about the structure of the western plateau to say whether
the course of the lower Housatonic could be accounted for on such an
hypothesis. On this theory the Connecticut would be consequent upon the
Jurassic deformation, and revived by the post-Cretaceous uplift.

It may be suggested that the southeast courses are due to the tilting
of the peneplain at the time of elevation, the plateau now being, as
we have seen, much higher in the northwestern part of the state than
elsewhere. But the acceptance of this theory necessitates a degree of
smoothness and absence of even mild relief in the peneplain, which is
hardly possible. The present average slope of the plateau is but a
few feet per mile, and it seems incredible that so gentle a tilting
could force rivers as large as these to take new courses. Besides,
if the Housatonic and Connecticut were deflected, why were not the
smaller streams--the Naugatuck and Quinnebaug--also given southeastern
deflections? Clearly, this explanation is not the correct one.

_Superimposition._ It has been suggested that these courses may be
inherited from a Cretaceous cover, which formerly stretched over
Connecticut for a considerable distance, but of which no traces now
remain in the state. On parts of Long Island the Cretaceous deposits
are found, and it is not inherently impossible nor improbable that they
once stretched far over the main land. In New Jersey[46] several lines
of evidence seem to show that the Cretaceous beds formerly extended
across the Triassic, probably to the margin of the highland plateau.
The curious drainage of the Watchung Crescent is one evidence of this,
but the other proofs are along entirely different lines, so that
there is apparently good evidence that the Cretaceous beds extended
twenty-five miles or more farther inland. If, in the time which has
elapsed since the deposition of these beds, there has been erosion
sufficient to strip them off from such a broad area in New Jersey, may
they not, in Connecticut, under presumably similar conditions, have
been equally eroded?

There is much which makes this hypothesis attractive, and, as the
facts were first studied, it seemed the most likely one. It affords
a good explanation, not only for the courses of the Housatonic and
Connecticut, but also for other rivers along the sound. It seems, also,
at first thought, to be well supported by analogy from New Jersey.
But a closer study of the situation in that state reveals marked
differences in the attendant circumstances. There the soft Triassic
sandstone must have been worn down to a lowland early in the Cretaceous
cycle, perhaps by the close of Jurassic time or thereabouts, while the
harder crystallines retained a strong relief. The slight subsidence,
which marked the beginning of marine Cretaceous in New Jersey, allowed
the Cretaceous sea to transgress rapidly the baseleveled sandstones to
the foot of the crystalline hills, but not to cover them to any extent.
It is not probable that the crystallines in Connecticut had been
brought nearer to baselevel than those in New Jersey at the time of the
Cretaceous deposits. There is no evidence to show that the subsidence
was greater in Connecticut than in New Jersey, and, therefore, from _a
priori_ considerations, the conclusion would seem to follow that the
subsidence, which permitted the Cretaceous sea to cover the Triassic
sandstone area of New Jersey, was not sufficient to permit the sea to
cover the then unsubdued crystalline hills of Connecticut. Although
this hypothesis is not to be hastily thrown aside, for theoretical
reasons, yet it would seem necessary to hold it very lightly, at
least until some positive proof is found of the former existence of
the Cretaceous or some later formation in that region. The first
suggestion, that the lower Connecticut was a consequent river in the
Cretaceous cycle and was revived by the post-Cretaceous uplift, is, at
the present state of knowledge, the most probable.

_The Farmington._ The roundabout course of this river presents another
interesting problem, which is not free from difficulties. From its
source in Massachusetts it flows southeast across the crystallines
to the village from which it takes its name, where it turns abruptly
north along the Triassic sandstones for ten or twelve miles, when with
another wide sweep it crosses the trap ridges at Tariffville by a deep
gorge, and resumes its southeasterly course to the Connecticut. Of this
latter part I will speak later, but now arise the questions, “what
has been the history of this river,” and “why does it turn north at
Farmington?”

_The Farmington in the Tertiary cycle._ A course more accordant with
the structure would seem to be south along the Quinnipiac and Mill
river valleys to the sound at New Haven. As has been said before
(page 376), Prof. Dana has expressed the opinion that the gorge at
Tariffville was occupied by the Farmington in Tertiary times, and that
the Westfield river gap further north and the gorge of the Quinnipiac
southwest of Meriden are also of earlier date than the glacial epoch.
One reason has also been given why I differ from him in regard to
the Quinnipiac and Tariffville gorges--they are narrower and steeper
than those made in similar rocks during the Tertiary cycle. But more
than this, the constructional topography, resulting from the tilting
and faulting of the region, could not, it would seem, have caused
the Farmington to take its present course. Even if it had taken
this roundabout course during the baseleveling of the country, it
must, since it would have had to cross three trap sheets, have been
captured and led to the sea by the shorter and easier way along the
sandstone area. The fact that the Connecticut probably persisted in
its consequent course is no argument for similar conditions for the
Farmington, because the latter is much the smaller stream, and so more
easily captured. Nor could the river have been forced into this course
during or after the post-Cretaceous uplift, for the land was then
raised more at the north than at the south, and any changes from this
cause would have been to confirm the river in its southward course. It
is very probable, therefore, that in at least the latter part of the
Tertiary cycle, the Farmington did not have its present course, but
followed the open sandstone valley, along the course of the Quinnipiac
and Mill rivers of to-day. The earlier history of this river is purely
conjectural; one fact may shed a little light upon it, a fact which may
indicate that this course was an adjusted one taken during Tertiary
times.

_In pre-Tertiary times. Origin of Cook’s Gap._ A few miles southeast
of where the river emerges from the crystallines, the trap ridge is
cut by a deep wind notch--Cook’s Gap--through which the New York and
New England Railroad passes west from New Britain. As was pointed out
some time ago by Prof. Davis,[47] this is not a fault gap, because the
alignment of the ridge is not broken, but it is probably an abandoned
water gap, the head-waters of the stream which formerly occupied it
having been abstracted by a rival, which did not have to cross a
hard trap ridge. Perhaps this river was the ancestor of the present
Farmington, and in that case its history would seem to have been
as follows. A stream consequent upon the constructional topography
after the faulting and tilting at the close of the Triassic, it had
its upper course on the crystallines, its lower on the sandstones
and buried trap sheets. In its old age it crossed by a shallow gap
the trap sheet, which had been uncovered by erosion. In the second
or Tertiary cycle it was simply a revived stream quickened to a new
life by the post-Cretaceous uplift of the peneplain. This uplift gave
opportunity to a rival stream, which did not have to cross the hard
trap beds to intercept the waters of the old Farmington, and lead them
out by a shorter, easier path, probably down the sandstone valley west
of the trap ridge. The path across the trap was abandoned, and the
notch became a wind gap; the river following its new course, until the
incursion of the ice-sheet interrupted its normal development. This is
of course almost entirely speculative. Cook’s Gap is best explained as
an abandoned river gap; the Farmington is the nearest river of a size
proportional to the size of the gap, and the hypothesis is a rational
one. There is, however, no direct evidence that the Farmington once
occupied Cook’s Gap.

_The Tariffville cut._ Before attempting to answer the second question,
“why the river flows north at Farmington?” let us consider for a moment
the history of the Tariffville cut. The river occupies a gorge whose
sides are steep and talus covered, but which is not at all clogged with
drift. There is naturally no room at or near the water level, even for
the wagon road, place for which has been blasted near the top of the
gorge. The profile of the gap shows a gentle ascent from the top of the
gorge, up to the nearly level crest line of the ridge. That is to say,
the recent gorge has been cut in the bottom of a sag in the ridge. We
have already given our reasons for believing that the gorge here is
much younger than the Westfield river gap; that it is a part of the
work of the next cycle; that it is post-Tertiary. The sag, however, in
the bottom of which the gorge is cut, is clearly of the earlier cycle.
The bottom of the sag is much above the level to which the rivers had
cut their valleys in the late Tertiary, and, therefore, it is certain
that a river could not have occupied it at the close of that cycle.
It was probably an abandoned water-gap whose stream had been captured
in the same way and in the same cycle as the river, which formerly
occupied Cook’s Gap.

The fact that the sag and gorge, although located very near a fault
line, do not correspond to it, but are transverse and independent of
it, is instructive and needs a moment’s attention. It seems probable
that the stream consequent upon the faulted blocks would have flowed
down the slope of the tilted block and then along the fault line at
the foot of the fault cliff and would have held this course during
the baseleveling of the country. When the area was baseleveled
the stream must have swung from side to side in its broad flood
plain, and thus departed from the fault line. When it was revived
by the post-Cretaceous uplift, it was confined to the course it had
unwittingly taken on the sandstones just above the hard ridge, and
it was forced to cut down through the trap. Subsequently a rival,
which did not have to work against this obstacle, abstracted its head
waters and the gap was abandoned. The accompanying diagrams may make
this easier to understand. Figure 3 is a cross-section of the faulted
monocline, R showing the position of the river along the foot of the
fault cliff. The line B L represents the surface of the country after
baseleveling, the trap outcrops forming _low_ hills (much exaggerated
in the diagram). Figure 4 shows the dislocated trap sheets, the fault
line and the winding course of the river, which has abandoned the
fault line except where it passes between the low trap hills. Here
the country is at baselevel. Figure 5 represents the region after the
elevation and resulting erosion. The trap ridges have become more
pronounced, and have migrated eastward in the direction of the dip. The
river has been slowly let down upon the northern one from the sandstone
at point G and has there cut into the solid trap.

[Illustration: FIGURES 3–5.]

The transverse notch of Cook’s Gap, already described, was probably
located in a somewhat similar manner, but the case is not so clear as
at Tariffville.

_Gravel terraces of the Farmington._ A consideration of some facts
concerning the height and slope of the terraces along this part of the
river may give a clue to the answer to our question. One-half a mile
east of Tariffville and east of the trap ridge, the highest terrace is
210 to 215 feet. Half a mile south of the same place but west of the
ridge the height is 275 feet.[48] The top of the gorge at Tariffville
is about 190 feet above the sea-level. It does not seem probable that
these highest terraces were ever continuous over all the Farmington
valley. But if they represent the level reached by the maximum flood
accompanying the melting of the glacier, the great difference in their
height on the two sides of the trap ridge, in connection with the
other evidence already noted, gives strong reason for believing that
the gorge as it exists to-day had not then been cut. A mile and a half
east of Tariffville there is a lower terrace which is wide-spread. Its
general height is about 190 feet, in places a little more. In this
terrace the lower part of the Farmington has cut a trench 90 to 100
feet deep. The shape of the valley makes clear the fact that before
this trench was cut the river flowed at about the 190 foot level, which
is the height of the bottom of the sag at Tariffville. On the west side
of the trap ridge there is also a more or less wide-spread terrace
at about the same height. It seems very probable therefore that the
river was raised to the level of the old sag in the trap ridge by the
building of these terraces.

The present average southward slope of the highest terraces west of the
trap ridge from Northampton, Mass., to Farmington, Conn., forty-four
miles, is seven inches per mile,[49] and Professor Dana is inclined to
believe that this is approximately the slope at the time the terraces
were built. The character of the deposits shows that the current
which formed these deposits flowed south. The present river, flowing
north, falls twenty feet between Farmington and Tariffville, or 1⅔
feet per mile. The reversal of the river was probably determined by
two factors. Near the village of Farmington, the waters of 200 square
miles of territory are poured into the valley by the upper Farmington
and its tributary, the Pequabuck. During the terrace building stage
the great mass of débris contributed by these streams was deposited
where the steep gradient of the highlands was exchanged for the gentle
slope of the lowland. The main north and south valley was thus choked
by the débris of its tributaries and a long stretch of comparatively
still water extended north from Farmington, in which nearly horizontal
deposits were made. South of Farmington the terrace deposits are
much coarser than to the north, and the face of the terraces is much
greater. It is not impossible that, as the deposits between Farmington
and the Massachusetts state line approached nearer and nearer to
horizontality, the waters of the upper Farmington began to divide, part
flowing north and part south, the northward flowing portion finding an
outlet at the sag at Tariffville. If this was the case, the terraces
between Farmington and Tariffville must have had a slight slope to the
north. Their present southward slope could readily be accounted for by
the re-elevation of the land after the disappearance of the ice. This
explanation rests upon the ability of the upper Farmington and the
Pequabuck to have completely dammed the southward flowing current and
turned it northward by the great mass of their deposits. If this was
not the case, and there may be some doubt on the matter, the subsidence
which accompanied the later stages of the ice-retreat is the other
factor in the problem. It is estimated that an average depression of
1.25 feet[50] through the Connecticut valley would restore it to an
altitude approximating that at the close of glaciation. It seems highly
probable that these terrace-deposits were built before the maximum
depression was reached. If this was the case, the depression would be
efficient in reversing the Farmington, and this factor would supplement
the first. It is impossible at present to say to what extent these two
factors enter into the problem. That they are not mutually exclusive
is evident, and that they are together quantitatively competent seems
certain. Among the several hypotheses which have been considered, this
seems the most probable, and in the light of the present evidence the
most rational.

At first thought it might seem that if the Farmington was reversed by
the differential subsidence of the land, the Connecticut ought to have
suffered a similar fate, and since it did not, the explanation cannot
apply to the Farmington. But the terraces of the Connecticut have a
much greater southward slope than those on the smaller river, and the
depression was not sufficient to reverse the stream. The conditions on
the two sides of the trap ridge were not the same.

To sum up, then, the history of the Farmington seems to have been
as follows: Its original consequent course was southeast on the
crystallines and perhaps across the trap ridge at Cook’s Gap, from
which course it was turned in the Tertiary cycle by a stream whose
course was approximately that of the Mill river of to-day. The damming
of the valley by the deposits of the Upper Farmington, and the
depression in the north accompanying the ice retreat, reversed the
river at Farmington, and it took a new course on the terrace deposits,
escaping by the sag in the trap at Tariffville into the Connecticut
valley.

_The Quinnipiac._ The gorge of the Quinnipiac, already mentioned
several times, seems closely comparable to the gorge of the Farmington.
It is not of the Tertiary cycle, and is best referred to the
inter-glacial or post-glacial epochs. We should expect the Quinnipiac,
instead of turning eastward, to cut through this sandstone ridge, to
continue southward along the Mill river valley. Dana[51] finds from
the heights of the terraces that the drainage of the terrace-building
period was not along the Quinnipiac, but along the Mill river, and
concludes that the Quinnipiac gorge was obstructed by an ice-dam. I
have not as yet studied it enough in detail to do more than express the
opinion here reiterated, that this gorge is later than the cycle in
which the open sandstone lowland on either side of it was excavated.
Its topographic form would put it in the cycle which has been called
post-Tertiary.

_The Scantic._ In the Scantic we have a typical example of a river
whose lower course is manifestly of a later date than the upper. In
this it is similar to several of our Atlantic rivers, notably those of
North Carolina, whose upper courses are on the Piedmont crystallines,
being probably established previous to the Cretaceous baseleveling, and
whose lower courses stretch seaward over the unconsolidated Tertiary
deposits of the coastal plain. As the plain of these recent deposits
emerged from the sea, the rivers were forced to extend their courses
eastward over the freshly raised surface to the retreating shore
line. The Scantic river has a similar history. Its upper course in
southern Massachusetts on the crystalline plateau is a remnant of the
drainage established before Cretaceous baseleveling and revived by the
subsequent uplift. How much that revived drainage has been modified by
drift can only be determined by long field study, but the topography,
as read from the topographical atlas would seem to indicate, that it
has not been much. The valleys were undoubtedly clogged with drift, and
the drainage area may be somewhat modified, but the drainage seems to
be substantially along the same lines.

Just below the village of Hampden, the Scantic leaves the plateau
and enters the Triassic lowland. From this point to its mouth at the
Connecticut, opposite Windsor, a distance of twenty miles, it flows
nearly all the way through the gravel, sand and clay deposits of the
period of ice-retreat. The topography of the lower course of the river
is entirely characteristic of a stream which has recently attacked a
level, easily eroded district. The inter-stream surfaces are broad and
flat; the descent to the stream bed which is sunk seventy or eighty
feet below the general surface is exceedingly steep. These two lines,
that of the inter-stream surface and that of the valley side, meet at
a sharp angle. The side streams are as yet very short, and have cut
narrow gorges down to the main river. Tributary to them are deep side
ravines, whose bottoms ascend rapidly to the inter-stream surface, the
whole making a dendritic system of drainage in its earlier stages. The
Scantic, having reached base level in its lower course, has developed a
narrow flood-plain.

Manifestly this part of the river valley is of much later date than
the upper part. If, during the period of ice-retreat, the lower
Connecticut valley was an estuary, the Scantic was a much shorter river
than at present. Its mouth could not have been far from the point
where now it leave the crystallines, but as the land was elevated and
estuarine conditions gave place to fluviatile, the Scantic lengthened
“mouthward,” consequent upon the minor inequalities of the newly made
beds. The effect would be substantially the same if the terraces
were built by great valley floods, as Dana supposes. In pre-glacial
times this river, in common with several other rivers rising on the
crystallines and flowing into the Connecticut, had courses of various
lengths over the Triassic sandstones, but these old valleys are lost
entirely, the later trenches in the terrace deposits being altogether
independent of them.

_Other examples._ The lower Hockanum, Farmington, Park, and the entire
length of many short streams are similar to the lower Scantic, and
originated under similar conditions. Stony Brook, a little stream
north of Windsor Locks, presents the same features, but with this
variation: It is superimposed through a thin layer of drift upon
the sandstone, into which it has cut a deep, picturesque gorge. The
Hockanum and Farmington are also “locally superimposed” in a few
places. The Connecticut, also, north of Middletown, although following
its pre-glacial valley, has departed in numerous places from its former
bed, and has cut down through the valley-filling onto ledges of rock
beneath. The water-power at Enfield, Conn., and at Turner’s Falls and
Bellows Falls, Mass., is the result of this superimposed position.

_Abandoned gaps._ Many abandoned water-gaps must exist among the hills
of the state. Cook’s Gap, through which the New York and New England
Railroad crosses the trap ridge, three miles west of New Britain, has
already been discussed. It must not be confounded with the majority
of the other gaps in the trap ridge, which are oblique, break the
alignment of the ridge, and are due to faults.

The New York and New England Railroad in ascending to the eastern
plateau passes through Bolton Notch, a few miles east of Manchester.
This notch, also, is an abandoned river bed but, as it seems, abandoned
at a later date and for another reason than that assigned for Cook’s
Gap. The drift is very heavy in this region, and the most probable
explanation is that the post-glacial streams do not altogether follow
pre-glacial valleys. This gap, used by turnpike and railroad, testifies
of another and older drainage system.

That in this brief article all the problems connected with the
Connecticut rivers have been solved, or even noted, is not to be
expected. It is hoped, however, that the work done may prove a help to
further study of the same regions, and that the tentative conclusions
advanced may be substantiated by further investigation.

                    HENRY B. KUMMEL.


FOOTNOTES

   [33] The author desires to express his obligation to Professor
        W. M. Davis for aid in the preparation of this article. It
        was first written under his direction and with the help of
        his suggestions when the author was in the graduate school of
        Harvard University. Prof. Davis is not responsible, however,
        for the statement of the views herein advanced, although in
        general it is believed that he is in accord with them.

   [34] Amer. Jour. Sci. 3d ser., vol. xxxvii, 1889, p. 423. Bull.
        Geol. Soc. Amer., vol. ii, p. 545.

   [35] The rough diagrams accompanying this paper may aid the
        reader who is unacquainted with the details of the region
        under discussion. The abbreviations on the above figure are
        as follows: C. The Connecticut. Cr. Pl. Crystalline plateau
        (the shaded area). F. The Farmington. H. Hartford. Ho. The
        Housatonic. Lm. Limestone area. M. Meriden. Mi. Mill River. Mt.
        Middletown. N. The Naugatuck. N. H. New Haven. No. The Norwalk.
        Q. The Quinnipiac. Qg. The Quinnebaug. S. The Scantic. Sa. The
        Saugatuck. T. Tariffville. Th. The Thames. The unshaded area
        is the Triassic sandstone lowland, and the blackened areas
        represent the ridges of the faulted trap sheets.

   [36] Am. Jour. of Sci., 3d ser., vol. xxxvii, p. 430.

   [37] Bulletin of Geol. Soc. of Amer., vol. ii, p. 554.

   [38] It is not desired to affirm that these periods of erosion and
        elevation began and ended promptly with the beginning or end
        of a period. The time statements must be considered as only
        approximate.

   [39] An exaggerated idea must not be had of the steepness and
        narrowness of these crystalline valleys. The valley of the
        Farmington, five miles up from where it opens into the Triassic
        sandstone, is 400 to 500 feet deep, and a mile and a half wide
        at the top. The Connecticut valley, just below Middletown, is
        about 400 feet deep and two miles wide at the top. These are
        fair representatives of the valleys in the crystalline rocks in
        the central part of the state.

   [40] Amer. Jour. of Sci., vol. x, 3d ser., 1875, p. 506.

   [41] McGee. Amer. Jour. Sci., 3d ser., vol. xxxv, p. 376.

   [42] Davis and Wood, Geographic Development of Northern New Jersey,
        pp. 413, 414.

   [43] “Rivers and Valleys of Pennsylvania,” Davis, W. M., published
        in The National Geographic Magazine, in 1889.

   [44] Davis, W. M., “Geographic Development of Northern New Jersey,”
        p. 397–8.

   [45] Davis, W. M., Amer. Jour. of Sci., 3d ser. vol. xxxvii., 1889,
        p. 432.

   [46] Geog. Devel. of Northern New Jersey, p. 404 et seq. Proc. Bos.
        Soc. Nat. Hist. Also Rivers of Northern New Jersey, p. 11 et
        seq. National Geographic Magazine, vol. ii, p. 93.

   [47] Faults in the Triassic Formation near Meriden, Conn. Bulletin
        of the Mus. Comp. Zoöl. Harvard Univ. vol. xvi. No. 4, p. 82.

   [48] J. D. Dana, Amer. Jour. Sci. 3d. ser., vol. xv, p. 506.

   [49] J. D. Dana, Amer. Jour. of Sci. 3d ser. vol. xxv, p 446.

   [50] J. D. Dana, Amer. Jour. of Sci., 3d ser., vol. xxiii, p. 198.

   [51] J. D. Dana. Amer. Jour. Sci., 3d ser., vol. xxv, p. 441.




_STUDIES FOR STUDENTS._

GEOLOGICAL HISTORY OF THE LAURENTIAN BASIN.


The study of the Pleistocene history of the basin drained by the St.
Lawrence has been fragmentary and is still far from being complete.
There is a lack of agreement in the interpretation of observations
already made, due in part to the comparatively limited portion of the
field examined even by those who have given the subject most attention,
and in part to lack of uniformity in the standards of comparison used.
It is with the hope of assisting in reaching more harmonious results
that attention is here invited to methods of study.

In the present treatment of the subject it may be advantageously
subdivided, and the facts and hypotheses relating to each division
separately considered. Of the divisions that may be suggested the
following seem the most important:

1. Character of the sub-morainal or hard-rock topography in the
Laurentian basin.

2. Origin of the basin.

3. Sedimentary deposits.

4. Shore markings left by former water-bodies.

5. Fossils in ancient sediments, shore ridges, terraces, etc.

6. Fauna of the present lakes.

7. Changes in elevations of the land.

8. Former outlets.

9. Probable effects of an ice sheet on drainage.

10. Probable effects of a subsidence which would make the basin an arm
of the sea.

1. _Character of the hard-rock topography._ In order to learn the
character of the Laurentian basin it is necessary to examine the
rock surface beneath the general covering of glacial débris and
stratified sediments which partially fill it. To do this, those areas
in which rock in place forms the surface require to be mapped and
their elevations noted; the records of wells and other excavations
which pass through the superficial deposits should also be obtained
and the character of the underlying rock ascertained, as far as is
practicable. When sufficient data of this nature shall have been
recorded, a contour map of the basin can be drawn that will reveal the
shape of the depression with which the student has to deal. The depth
of the present lakes plus an estimated thickness of clay and morainal
material covering their bottoms, will probably furnish the only means
of sketching contours over the deeper portions of the basin. Even an
approximately accurate map of this character cannot be constructed for
a long time to come, but every advance towards it will serve to make
the problems to be studied more and more definite.

Something of the form of the rock-basin is already known and several
deep channels in its borders, now filled with drift, have been
discovered. The courses of buried channels connecting the basins of
some of the present lakes have also been approximately determined. It
is not necessary at this time to refer specifically to the discoveries
that have been made, but it may be stated that enough is known to
assure us that the basin is a depression in solid rock, the bottom of
which is below sea level.

2. _Origin of the basin._ The rocks in which the Laurentian basin
is situated are, with the exception of the Lake Superior region,
nearly horizontal and belong almost wholly to the Paleozoic. The
basin is essentially a depression in undisturbed strata, and all who
have considered its origin seem agreed that it has been formed by
excavation. A vast mass of horizontal strata has been removed, leaving
an irregular rim of undisturbed rocks on all sides. The form of the
depression is now obscured by drift; the deeper portions contain
stratified sediments which have been deposited within it and it has
been warped somewhat by orographic movement.

The manner in which the excavation was formed has been explained
principally in two ways. One hypothesis is that it owes its origin to
a time of subaërial denudation preceding the Glacial epoch, during
which a valley, or series of valleys, was worn out by stream erosion;
and that the depression thus produced has been but slightly modified
by ice action. The closing of the ancient valley has been referred
to orographic movements and to the filling of its outlet by glacial
débris. Another hypothesis is to the effect that the excavation is
mainly due to ice erosion during the Glacial epoch, without special
reference to previous topographic relief. A warping of the earth’s
crust so as to produce a true orographic basin does not seem to require
consideration, for the same reason as already stated, that the rocks in
which the basin lies have been but little disturbed from their original
horizontal position. Future study of the region must determine which
of the two hypotheses outlined above best suits the facts; or if each
hypothesis has something in its favor, what combination of the two may
be accepted as the final explanation.

It is a suggestive fact in connection with the first of these
hypotheses, that the youngest rocks in the region antedating the
Pleistocene belong to the Carboniferous. This seems to show that the
land has not been submerged since at least the close of the Paleozoic.
If not a region of sedimentation during this vast interval, it must
have been subjected to erosion. The erosion of an ancient land surface
might result in the production of topographic forms of diverse
character, depending on its altitude, on the length of time it was
exposed to atmospheric agencies during various stages of elevation, and
on climatic and other conditions. The study of topographic forms is
now sufficiently advanced to enable one to predict somewhat definitely
what features would appear under certain conditions. We also know the
characteristics of topographic forms due to glacial erosion. It seems
evident, therefore, that a knowledge of the hard-rock topography in
the Laurentian basin, would enable one to draw definite conclusions in
reference to the part that ice and water each had in shaping the forms
now found there.

The conclusion that the region under consideration has been glaciated
is well established; it remains, therefore, to determine what
topographic forms, if any, due to pre-glacial stream erosion can be
recognized. As an example of this kind of evidence desired, attention
may be directed to the northward facing rock escarpments which follow
the southern shores of lakes Erie and Ontario for a large part of their
courses and at varying distances up to several miles. These escarpments
are composed of the edges of nearly horizontal strata, mostly of
Paleozoic limestone, and their bases are buried beneath glacial débris
and stratified clays so deeply that in some instances, at least, they
do not reveal half of their actual height. These escarpments not only
have Pleistocene deposits banked against them, but their faces and
summits are polished and grooved, showing how stubbornly they resisted
the invasion of the ice which impinged against them from the north.
South of lake Ontario especially, the trend of the escarpment referred
to is directly athwart the course of the ancient glaciers. The entire
history of these escarpments cannot be discussed here, as my desire
is simply to call attention to the fact that they existed before the
Glacial epoch, and are relics of a strongly accented pre-glacial
topography. They are within the southern border of the Laurentian
basin, and hence afford means of determining, in part, what was the
form of that basin before it was modified by ice action. Other similar
escarpments exist in the northern and western portions of the same
great basin, and as this study progresses it is to be expected that
still other features of the pre-glacial land will be revealed. It is
perhaps too early to decide what were the special topographic forms
which gave character and expression to the St. Lawrence basin before
the ice invasion, but the Erie and Ontario escarpments and some other
similar features now recognized, suggest that in Tertiary times it
resembled the present condition of the upper portion of the Mississippi
valley, where bold, rock escarpments border wide stream-worn
depressions.

Deep drift-filled channels are known to cut across the Erie and Ontario
escarpments. These seem to have been formed by streams tributary
to the main drainage line to the north. If this conclusion is well
founded, a study of the hard-rock topography should reveal other
similar channels and finally indicate a well matured drainage system.
If even the broader and stronger features of the pre-glacial surface
can be determined, then the modifications due to glacial abrasion will
become conspicuous, and the amount that glaciers have broadened and
deepened the basin be determinable.

A study of the lithological character of the drift south of the present
lakes should show, at least in a rough way, what portion of it was
derived from the waste of rocks within the Laurentian basin. This
inquiry has already been undertaken by at least two geologists, and
estimates of the quantity of material removed from the basins of lakes
Michigan and Erie respectively, have been made. This method may be
extended so as to embrace a larger area, or some special portion of
the great depression best suited for the trial may be selected. If the
material removed from the basin or re-distributed within it by glacial
action can be shown to be approximately equivalent in volume to the
amount of rock excavated in order to form the depression, it would
evidently tend to support the hypothesis of glacial erosion. If, on
the contrary, the amount of débris derived from the basin should fall
far short of what would be requisite to refill it, no very definite
conclusion would seem to be indicated unless account could also be
taken of the fine material carried away by glacial streams.

As the case stands at present it appears that there is evidence of a
pre-glacial valley or series of valleys as has been claimed by several
geologists, and that all but the boldest features of the old topography
have been obliterated or greatly modified by glacial erosion followed
by glacial and other sedimentation. Additional observations should
show somewhat definitely the amount of work assignable to particular
portions of the history. How far the results of subaërial and of
glacial erosion have been modified by other agencies, more especially
by orographic movements, has also to be considered.

If the St. Lawrence basin shall be shown to be largely the result of
subaërial erosion it will follow, unless it is found that the deeper
portions are the result of glacial action, that the land at the time
the streams did their work, must have stood higher than at present, for
the reason that the bottom of the depression is now below sea level.
Some idea of the smallest amount of elevation necessitated by this
hypothesis might be obtained by estimating the gradients of the ancient
streams and the amount of elevation required to bring the bottom of the
depression up to sea level.

A study of the hard-rock topography in the valleys of the Ottawa and
St. Lawrence and of the present submerged Atlantic border of the
continent would also be instructive in this connection. The strict
correlation of the topographic history of the interior and of the
continent’s margin may be difficult, but as the two regions are
directly connected, valuable results should follow their comparative
study.

The hypothesis that the Laurentian basin is due largely to pre-glacial
erosion, necessitates also that the ancient system of river valleys
should have been closed in some way so as to form the basins of the
present and of former lakes. The closing has been referred to several
agencies. An unequal subsidence following the period of stream erosion
has been postulated. During the Glacial epoch the entire region was
ice-covered and only glacial streams of one kind or another could
have existed. On the retreat of the ice, when portions of the basin
were abandoned, the drainage is supposed to have been obstructed by
the ice itself, as will be noticed below. When the glaciers melted,
a vast sheet of débris was left which in many instances filled or
obstructed previous drainage lines. Old channels, now deeply buried,
have been reported to connect the basins of the various existing lakes,
as has already been mentioned, but no similar channel which could
have afforded an escape for the waters of the entire basin has been
discovered. Here again an acquaintance with the hard-rock topography
should give assistance and indicate either that such a channel existed
or that orographic movements have taken place which have obstructed the
former drainage system. The glacial hypothesis assumes that the basin
was excavated mainly by glacial abrasion and does not require that
the land should be either higher or lower than at present. The study
in this direction merges with that of the general glaciation of the
northeastern part of the continent, and cannot be treated at this time.

3. _Sediments._--Regularly stratified deposits of clay and sand occur
along many portions of the borders of the present Laurentian lakes.
These were clearly formed in water bodies which formerly existed within
the Laurentian basin, and which in certain directions, at least, were
of wider extent than the present lakes. The areas occupied by these
deposits have been partially mapped, but much remains to be done in
this direction. Fresh sections, particularly of the stratified clays,
are exposed from time to time by artificial excavations, in which much
of their history may be learned. Not only should records be made of the
facts noted at special excavations, but the extent and character of the
stratified deposits in one area should be determined and compared with
similar data obtained in other areas. For example: the clays covering
large tracts on the west shore of Lake Michigan and on the southern and
western border of Lake Superior are of a red color, while other areas
bordering Lake Erie are covered with blue clay. These two deposits
have been supposed to have been laid down at the same time and in the
same lake. The definite correlation of the clays of these two areas by
direct contact, however, does not seem to have been made, and there
are reasons for thinking that they may be quite distinct and that they
originated in separate lakes.

The outer limits of the deposits of clay and sand here referred to
are known in some instances to be determined by ancient beaches and
terraces. Such associations of deep and of shallow water deposits
require special attention, as the study of one may assist in
interpreting the significance of the other. The fine, evenly stratified
clays frequently contain large angular bowlders, which appear to have
been dropped from floating ice and to show an intimate connection
between the ancient lakes and neighboring glaciers. The possibility,
however, of the bowlders having been brought into the ancient water
bodies by rivers, or floated outwards from the shore by lake ice,
should also be considered. Huge angular masses of limestone have been
reported as occurring in southern Michigan especially, which rest on
superficial deposits and are thought to have been carried northward by
lake ice. The relations of these masses to well defined shore lines
have never been determined. If it should be found that they are above
all former shores, it is evident that they must have been carried by
some other agency than the one mentioned.

A chemical examination of the clays, or of their contained water, may
indicate whether or not the basin was formerly in direct communication
with the ocean. Analyses of the clays of the Champlain valley and of
the similar clays in the Ontario and Erie basins might indicate whether
or not they were deposited under similar conditions.

4. _Shore records._ Beaches and terraces have been studied at many
localities about the borders of the present lakes, sometimes at a
distance of more than twenty miles from their margins and at various
elevations up to several hundred feet above their surfaces. In some
instances these ancient shore records have been followed continuously
for scores of miles. The tracing and mapping of individual beaches is
one of the most important parts of the study here outlined, and is
already well advanced. Confusion has unfortunately arisen, however, for
the reason that topographic features, due to shore action, have, in
some instances, been confounded with somewhat similar features due to
other causes. Moraines and gravel ridges, formed by glacial streams,
have been mistaken for beach ridges, and terraces of various origin
have not been clearly discriminated.

In order not to be led astray by topographic forms that simulate shore
phenomena, the student should examine the shores of existing lakes and
learn what records are there being made. In the study of topography,
“the present is the key to the past,” just as definitely as in any
other branch of geology. The topography of lake shores has already
received attention from one skilled in reading geological history in
the relief of the land[52] and the study of existing shores in the
light of what has already been done in that direction should enable
even the beginner to avoid falling into serious error in interpreting
ancient records of the same nature.

To be able to discriminate clearly between shore features and somewhat
similar glacial phenomena, it is necessary to become familiar also with
the topography of glacial deposits. Fortunately in this study also a
guide is at hand[53] which, in connection with field observations,
should soon train the eye to discriminate the shapes assumed by
moraines and the deposits of glacial streams from all other topographic
forms.

In examining the records of former lakes it will soon be observed that,
in many instances, where the highest of a series of ancient beaches
is obscure and indefinite, the topographic expression above and below
a certain horizon, and also the character of the surface material,
whether of the nature of lacustral clays and sands or of glacial
débris, residual clay, etc., above and below the same level, are
significant, and enable one to map the outline of a former water body
with considerable accuracy.

In tracing ancient beaches and terraces, their forms and internal
structure need to be recorded, so that the fact of their being true
shore records may be made plain to others. The elevations of various
well-defined points throughout the extent of an ancient shore should be
carefully measured, for, as will be noticed below, although originally
horizontal, they have, in many instances, been elevated or depressed,
owing to broad general movements of the earth’s crust. The continuous
tracing of individual shore lines for as great a distance as possible
is highly desirable, especially in a wooded country, in order to be
positive as to which ridge or terrace measurements of elevation relate,
and also for the purpose of observing the nature of the changes that
occur when a shore line gives place to other records. For example: some
of the ancient beach ridges about the west end of Lake Erie have been
found to be continuations of moraines. In other instances shore ridges
have been reported to end indefinitely and to be replaced at the same
general horizon by glacial records of various character. The correct
interpretation of phenomena of this nature is especially important.

Accurate measurements of the vertical intervals between well defined
beaches at many localities would enable one to identify special
horizons, providing orographic movements were not in progress during
the time the series was forming. This method has recently been
successfully applied on the north shore of Lake Superior, where the
character of the country does not admit of the tracing of individual
terraces for considerable distances.

The deltas of tributary streams should also be revealed in the
topography of the basin of an ancient water body. Changes in the
character of lacustral sediments near where rivers emptied are also to
be looked for. Sand dunes are frequently an important accompaniment of
existing shores, and their association, perhaps, in a modified form,
with ancient beaches is to be expected.

5. _Fossils._ Thus far only a few fossils have been found in the
stratified clays and sands or in the ancient beaches of the Laurentian
basin. Such observations as have been made in this connection indicate
an absence of the remains of marine life and the presence, in a few
instances, of fresh-water shells in all of the basin west of the
eastern border of the basin of Lake Ontario. To the eastward of Lake
Ontario, however, in the St. Lawrence and Champlain valleys, marine
fossils are common in deposits supposed to be contemporaneous with the
stratified clays to the west.

A careful search in the clays and beaches left by the former water
bodies might be rewarded by important discoveries. In this examination
microscopical organisms should not be neglected. If after a detailed
examination no fossils are discovered, this negative evidence would
have its value, as it would indicate that the physical conditions were
not favorable to life, and an explanation for this fact might be found.
It is scarcely necessary to mention that care should be taken not to
mistake the shells occurring in modern swamp deposits associated with
the ancient beaches for true lacustral fossils.

About the borders of the present lakes and sometimes even below the
level of the lowest of the ancient beaches the remains of the mastodon,
elephant, giant beaver, elk, bison, deer, etc., have been found. The
recency of the existence of such of these animals as are extinct may
thus be established, as well as the former distribution of those still
living in other regions.

Evidence of the existence of man has been reported from one of the old
lake ridges in New York, and it is important that this interesting
discovery should be sustained by evidence from other localities. Stone
implements especially should be looked for in undisturbed lacustral
clays, and in the gravels of the ancient beaches.

The remains of forests have been stated to occur in the lacustral clays
adjacent to the south shore of Lake Erie. It is desirable to know
the extent of these deposits and how continuous they are; also the
character of the plant remains they contain, and whether they have been
disturbed from the position in which they grew. Some of the questions
that may be asked in this connection are: Was the basin drained and
forest covered before the vegetable remains were buried, or were the
plants floated to their present position, or did they grow on moraines
covering the stagnant border of the retreating glacier and become
involved and buried in morainal material as the ice melted?

6. _Life in the present lakes._ The fauna of the present lakes has
a bearing on their past history, for the reason that in the deeper
parts of lakes Superior and Michigan crustaceans and fishes have been
found which are believed to be identical with marine forms. These
may be considered as “living fossils,” and are thought by some to
indicate that the lakes in which they occur were formerly in direct
communication with the ocean. If the occurrence of living marine
species in the present lakes is found to be widely at variance with
the history of the basin as determined from physical evidence, an
inquiry should be made in reference to the manner in which the species
discovered might migrate.

7. _Changes in elevation._ One of the most difficult problems in
connection with the history of an inland region is the determination of
changes of level. By leveling along an ancient beach, post-lacustral
changes in the relative elevations of various points may be readily
ascertained. Pre-lacustral changes, however, by which ancient valleys
have been obstructed, are much more difficult of direct observation,
but might appear from the study of the hard-rock topography, as has
already been suggested. This branch of the investigation, however,
should more properly begin at the coast and be extended inland.

8. _Former outlets._ Several localities where the waters of the
Laurentian basin have overflowed during former high-water stages have
been pointed out, but some confusion has arisen in this connection,
for the reason that the channels formed by streams issuing from the
margin of the ice during the closing stages of the Glacial epoch have,
in some instances, been mistaken for evidence of former lake outlets.
The old outlets which seem to have been well determined are situated at
different levels, and show that the entire basin could not have been
occupied by a single great water-body, unless, as has been supposed
by some, it was in direct communication with the sea. This hypothesis
will be considered below. It has sometimes been assumed that all of the
basin below the level of some ancient outlet was once flooded, so as to
form a great lake in all of the basin now situated at a lower level;
but, in making such generalizations, the possibility of places in the
rim of the basin being at a lower level than the outlet discovered,
thus necessitating a special explanation, such as the partial
occupation of the basin by glacial ice, or changes in elevation of such
a character as to raise the locality of former overflow or to depress
other regions, have to be considered.

Former outlets should bear a definite relation to neighboring shore
lines and to sedimentary deposits. The channels leading from former
points of discharge merit examination, as here again changes of level
may perhaps be detected in the gradients of stream terraces.

Most of the ancient outlets thus far recognized lead southward, but
as previously mentioned, a former channel of discharge north of Lake
Superior has recently been reported. If this observation is confirmed,
it will have an important bearing on questions relating to changes of
level and to the position of the ice front during the later stages in
the retreat of the glaciers.

9. _Probable effects of a retreating ice sheet on drainage._ The
generally accepted conclusion that glaciers advanced southward and
occupied the Laurentian basin during the Glacial epoch and retreated
northward toward the close of that epoch, is sustained by a vast body
of evidence. As the ice sheet withdrew it left a superficial deposit
frequently one or two hundred feet thick over nearly all of the region
it abandoned, and pre-glacial drainage lines were obstructed and mostly
obliterated. As long as the slope in front of the ice was southward,
the drainage from it found ready means of escape, but when the slope
was northward towards the ice front, the drainage was obstructed and
lakes were formed.

We have good reasons for believing that the topography of the
Laurentian region was essentially the same at the close of the Glacial
epoch as it is now, but the broader question of continental elevation
is less definite. The inequalities of the surface being essentially as
we now find them, it would follow that the first lake formed when the
ice retreated to the north of the divide running through central Ohio
and central New York, would be small and dependent on minor features
in the relief of the land, and would discharge southward. As the ice
retreated, the lakes would expand and become united one with another
and the larger lakes thus formed would still find outlet across the
southern rim of the basin. As the glaciers continued to retreat lower
and lower, passes would become free of ice and the lakes would be
drained at lower levels, old beaches would be abandoned, the lakes
would contract, and finally separate lakes would be formed in the
lowest depression in the basins of the more ancient water bodies. The
shape of the retreating ice front would be determined by topographic
conditions and would in turn determine the northern outline of the
lakes along its margin. This in brief is one hypothesis that has been
proposed to explain the varied history recorded by the shore records,
sediments, etc., within the basin.

10. _Communication with the sea._ Another hypothesis which assumes
to account for some of the facts observed, is that the continent was
depressed at the close of the Glacial epoch sufficiently to allow the
sea to have access to the Laurentian basin. This hypothesis is coupled
with others which do not recognize a period of Pleistocene glaciation,
but, as already suggested, this is a matter that is considered by the
great body of American geologists as not being any longer open to
profitable discussion.

In the study here outlined the question whether the water bodies which
formerly occupied the Laurentian basin were lakes or arms of the
sea, should not be difficult of direct and positive determination.
If fossils can be found within the basin, they might yield definite
testimony, but even if they are absent or if their evidence is
inconclusive, topography can be appealed to with the expectation of
receiving a conclusive decision.

If the Laurentian basin was occupied by an arm of the sea during
various stages in the Pleistocene elevation, then the records of such
a submergence should occur both within and without the depression,
and direct connection between the two should be expected. If the
waters within the basin were capable of making such well-defined
shore records as are now found, we are justified in assuming that the
true ocean beach on the outer slopes of the basin would be still more
conspicuous. Again, the waters within the basin deposited a sheet of
sediment, certainly not less than one hundred feet thick; to be sure
the conditions for rapid accumulation were there present, but if the
ocean covered the adjacent land it should have left similar deposits.
This is abundantly proven in the St. Lawrence and Champlain valleys,
where clays containing marine fossils occur up to a certain horizon and
record a Pleistocene invasion of these depressions by the sea. If the
adjacent Ontario basin was occupied by the sea about the same time that
the Champlain valley received its filling of clays containing marine
fossils, there is every reason to believe that the deposits and their
contained fossils in each basin would have been essentially the same.

One of the best known of the ancient shore lines about Lake Ontario has
an average elevation of approximately 500 feet above the sea. If the
sea had access to the basin at the time this breech was formed, then at
corresponding horizon without the basin especially, to the south and
southeast, where the full force of the Atlantic’s waves would have been
felt, there should be still more prominent beaches.

Many well-defined shore lines in the Laurentian basin are much higher
than the one just referred to, and if these were also formed during
various stages of submergence, as has been claimed, it is evident that
ocean beaches and ocean sediments of Pleistocene age should be looked
for over nearly the whole of the eastern part of the United States. The
student may easily answer this question for himself, and thus perhaps
make a contribution to the subject here treated.

In the investigation here outlined, the work of previous observers
should not be ignored, and every plausible hypothesis that has been
advanced to account for the facts observed should be carefully tested.
In writing these pages I have not quoted the writing of others, for the
reason that a discussion of evidence has not been the aim in view, and
also because the writings examined are so numerous that justice could
not be done them in the space at command. That the literature relating
to the subject is voluminous is indicated by the fact that an annotated
bibliography of the Pleistocene history of the Laurentian basin, now in
preparation, already contains over 200 entries of individual papers.

                    ISRAEL C. RUSSELL.


FOOTNOTES

   [52] The Topographic Features of Lake Shores, by G. K. Gilbert, in
        Fifth Ann. Rep. U. S. Geological Survey 1883–4.

   [53] Preliminary Paper on the Terminal Moraine of the Second Glacial
        Epoch, by T. C. Chamberlin, in Third Ann. Rep. U. S. Geological
        Survey, 1881–2.




_EDITORIALS._


The Summer meeting of the Geological Society of America will be held
at Madison, Wis., on August 15 and 16. The session of the American
Association for the Advancement of Science will begin at the same
place on the 17th of August and extend to the 23d. The Congress of
Geologists, under the auspices of the Columbian Exposition, will begin
at Chicago, on August 24, and continue its sessions so long as its
work may require. Preliminary to this series of meetings, Professors
M. E. Wadsworth and C. R. Van Hise will meet such geologists as care to
visit the Lake Superior region at the Commercial Hotel, Iron Mountain,
Mich., on the forenoon of August 7, and will act as guides during the
week following. A carefully prepared scheme for the trip is announced,
embracing visits to the leading points of interest in the Menominee,
Marquette and Gogebic iron districts, and in the copper-bearing region
of Keweenaw Point. Those who desire to participate in the excursion, or
who wish information regarding it, should address Professor Van Hise,
at Madison.

In connection with the meetings of the Geological Society and the
American Association at Madison, there will be excursions to the
Devil’s Lake region, to the Dells of the Wisconsin, and to the
driftless area, under the guidance of geologists personally familiar
with the features of most special interest. The article of Professor
Van Hise in this number is a timely presentation of some points of
peculiar significance in the first named region, and will prove very
serviceable to those who choose the excursion to that region.

It is proposed to hold the sessions of the Congress at Chicago at the
Art Institute during the forenoons, leaving the afternoons free for
visiting the Exposition. Experience has shown that a half day devoted
to looking at exhibits, where there is such a plethora of objects
of interest as in the Exposition, taxes the faculties of observation
to the full extent of their pleasurable employment. Attendance upon
the Congress and the study of the Exposition will, therefore, it is
thought, constitute agreeable and profitable complements of each other.
Excursions to points of geological interest in the vicinity of Chicago
will be privately arranged, if desired.

These three meetings, with the attending excursions and the study of
the Exposition, constitute a rare combination of opportunities which
will doubtless be embraced very generally by the geologists of the
country.

                    T. C. C.

  *.*

The supply of numbers one and two of this JOURNAL remaining in the
hands of the publishers has become reduced below the limit they desire
to preserve for binding and for special purposes, and they would esteem
it a great favor on the part of those who may have received duplicates,
as sample copies or by the accidents of mailing while the lists were
imperfect, if they would return such duplicates to them. They will
gladly return the postage if the address of the sender is placed on the
wrapper.




_REVIEWS._


CRYSTALLINE ROCKS FROM THE ANDES.

  _Untersuchungen an altkrystallinen Schiefergesteinen aus dem Gebiete
      der argentinischen Republik_ von B. KÜHN. Neues Jahrbuch für
      Min., etc., Beit. Bd. VII., 1891, p. 295.

  _Untersuchung argentinischer Pegmatite, etc._, von P. SABERSKY, _ib._
      p. 359.

  _Untersuchungen an argentinischen Graniten, etc._, von J. ROMBERG,
      _ib._, VIII., 1892, p. 275.

Travelers and foreign residents in South America are rapidly furnishing
information relative, not only to the volcanic, but also to the older
crystalline rocks composing the great Andes chain. Since the early
observations of Darwin,[54] the petrographical collections made by
Stelzner during his three years’ residence, as professor, at Cordova
(1873–1876) have been described by himself[55] and Franke,[56] while
the results of detailed studies of the more extensive collections
gathered by Stelzner’s successor, Professor L. Brackebusch, are now
beginning to appear. Professor Brackebusch’s residence in the Argentine
Republic lasted from 1876 till 1883, and during this period he made
numerous scientific expeditions.[57] The petrographical material
thus obtained has been confided to specialists in Germany for study.
Three papers dealing with the crystalline schists (gneisses),[58]
pegmatites,[59] and granites,[60] have recently appeared. The rocks of
the granite contact-zones had been placed in Professor Lessen’s hands
before his death, while communications on other special groups are
doubtless to be expected.

These investigations naturally suffer from the forced absence of
all field observations on the part of their authors, but the purely
petrographical study of the material brings to light many points of
interest, while it furnishes the only sort of detailed information
regarding the rocks of these remote regions which we can for the
present hope for. It is here desired only to direct attention to a few
of the most striking results obtained from the Brackebusch material by
the three authors last cited.

Dr. Kühn’s paper on the crystalline schists treats principally of
gneiss, and offers little that is new. It is mostly occupied with
additional evidence of structural and chemical changes due to dynamic
metamorphism in the sense of Lehmann. The most noteworthy of these are
development and microstructure of fibrolite; production of augen-gneiss
from porphyritic granite; development of microcline structure in
orthoclase by pressure; secondary origin of microcline, microperthite
and micropegmatite; alteration of garnet to biotite and hornblende.

Dr. Sabersky’s paper on the coarse-grained granites or pegmatites is
entirely mineralogical, and is devoted principally to elucidating the
structure of microcline. The author concludes that the well-known
gridiron structure is due, not to two twinning laws (the Albite and
Pericline), as has been generally supposed, but to the Albite law
alone, in accordance with which the individuals form both contact and
penetration twins, like the albite crystals from Roc-tourné, described
by G. Rose.

Dr. Romberg’s paper on the Argentine granites is much more
extensive than the two preceding. It is embellished by seventy-two
microphotographs, many of which admirably illustrate the special
points described. He comes to several results of great petrographical
significance, the most important of which relate to the origin of
quartz-feldspar intergrowths in granitic rocks. He clearly shows that
beside the original granite quartz there is also much of a secondary
nature present. This is not microscopically distinguishable from the
original mineral, but its later genesis is demonstrated by many careful
observations on its relation to other constituents. The abundant
secondary quartz is regarded as the product of weathering--principally
of the feldspar, into which it has a peculiar tendency to penetrate.
The extreme sensitiveness of quartz to pressure is emphasized (as
it has been by Lehmann and the present writer) and illustrated by
undulatory extinction, banding, granulation and even plastic bending
around other minerals. Dynamic action is regarded as the efficient
cause of the secondary impregnation of feldspar by quartz, and a union
of this with weathering of the feldspar as the source of the abundant
and complex pegmatitic intergrowths of quartz and feldspar.

These results are important, and they will now doubtless come to
be generally recognized. It is, however, of interest to observe in
this connection that all which is here announced as new in regard to
secondary and “corrosion” quartz was described and figured in even
greater detail by Prof. R. D. Irving ten years ago. This does not
appear to be known to Dr. Romberg, for he does not allude to it, but
anyone who will turn to pages 99 to 124 and plates XIII, XIV and XV of
the monograph on the Lake Superior Copper Rocks (vol. 5, U. S. Geol.
Survey, Washington, 1883) will find his conclusions stated in almost
the same language and with a much wider range of fact and illustration.
Dynamic action is not here adduced as a cause for the saturation of
feldspar by secondary micropegmatitic quartz, since the Lake Superior
rocks show no evidence of having been subjected to pressure, but
that the quartz itself has been derived from the leaching of the
feldspar substance and that the impregnation is mostly confined to the
orthoclase is clearly stated.

Dr. Romberg also demonstrates, in a number of cases, the secondary
origin of albite, especially as microperthite, and of microcline.
He gives details relating to each of the mineral constituents, and
then the effects of pressure and of chemical action on the most
important of them. Among many interesting observations but a few
can be even mentioned here; such, for instance, as the original
character of muscovite in many granites; the alteration of garnet
into muscovite; the dependence of the well-known pleochroic halos in
biotite and cordierite upon the substance of the zircon which they
almost invariably surround, and secondary rutile needles which grow
out from biotite into both quartz and feldspar. In one rock occurring
in a granite a violet, strongly pleochroic mineral was found, which,
in neither composition nor physical properties, agreed exactly with
any known species. It seems to be intermediate between andalusite
and dumortierite, but, as its individuality is not yet perfectly
established, no new name is proposed for it.

                    G. H. WILLIAMS.


  _The Mineral Industry, its Statistics, Technology and Trade, in the
      United States and Other Countries, from the Earliest Times to the
      End of 1892._ Vol. I. Edited by RICHARD P. ROTHWELL, editor of
      the _Engineering and Mining Journal_. 629 pp., 8vo.

This volume is a statistical supplement of the _Engineering and Mining
Journal_, and is published by the Scientific Publishing Co., of New
York, 1893. It takes the place of the former annual statistical number
of the _Engineering and Mining Journal_, and it is the first volume
of a series which is to be issued annually. The object of the present
volume is to make known, as soon as possible after the expiration
of the year 1892, the statistics and the various conditions of the
mining industry in that year and in previous years. The future volumes
will, each year, bring these statistics up to date, and thus the full
particulars of the mining industry will be known within a few days of
the expiration of every year. The volume is a compilation of articles
written by different authors, and the names of these writers are
guarantee that the different subjects have been treated by authorities
in the departments with which they deal. The editor himself, it is
but justice to him to state, has written some of the most important
parts of the volume, notably the article on the statistics of gold and
silver, and his well-known familiarity with the subjects he discusses
renders the reader confident of their accuracy.

The present volume is not confined to the bare presentation of figures
of production and consumption of various mineral products, but it
treats each individual branch of the mining industry in its various
departments; and in this way the volume really represents a series of
treatises on the various mining products and the methods of treating
them. The production of each material is given not only for the United
States but also for foreign countries; the conditions of the American
and foreign markets during 1892 and previous years are discussed, while
the various uses of the different materials, the history of mining in
different districts, the means of transportation, the metallurgical
methods of treating different ores, the methods of sampling, and the
possibilities of competition in various mining industries are also
described. In addition to this, tables of assessments levied and
dividends paid by various mining companies are given. The volume ends
with a concise statement of the statistics and condition, as well as
the extent, of the mining industries of foreign countries. Thus there
is presented, in a volume of no excessive size, a complete and concise
epitome of the mining industries of the world; and this work was
completed almost immediately after the time to which it relates.

The various subjects are treated in the following order: A résumé and
tables of statistics of the mineral products of the United States;
articles on Aluminum, Antimony, Asbestos, Asphaltum, Barytes, Bauxite,
Borax, Bromine, Cement, Chemical Industry, Chromium, Coal and Coke,
Copper, Corundum and Emery, Cryolite, Feldspar, Fluorspar, Gold and
Silver, Iron and Steel, Lead, Manganese, Mica, Nickel and Cobalt,
Onyx, Petroleum, Phosphate Rock, Platinum Group of Metals, Plumbago,
Precious Stones, Pyrites, Quicksilver, Salt, Soda, Sulphur, Talc,
Tin, Whetstones and Novaculite, Zinc; Tables of Assessments Levied by
Mining Companies from 1887–1893; Tables of Dividends Paid by American
Mining Companies; Baltimore Mining Stock Market, Boston Mining Stock
Market, Denver Mining Stock Market, London Mining Stock Market, Lake
Superior Mining Stock Market, New York Mining Stock Market, Paris
Mining Stock Market, Pittsburg Mining Stock Market, Salt Lake City
Mining Stock Market in 1892, San Francisco Mining Stock Market; Foreign
Countries--Austria-Hungary, Belgium, Canada, China, France, Germany,
Italy, Japan, Russia, South American Countries, Spain and Cuba, Sweden,
United Kingdom of Great Britain and Ireland.

The importance of the subject treated in this volume can be appreciated
when it is known that the products of the mines of the United States
alone in the census year of 1889 amounted to $587,230,662, and that
this amount really only represents the interest on an immensely larger
capital invested. The mining products of the United States are far more
important in their aggregate value than those of any other country in
the world, though, in many individual products, other countries supply
more than the United States. This country is first, however, in the
production of pig iron and steel. It is also first in the production of
copper, gold, silver, petroleum, and a number of other products. Great
Britain is still the leader in the production of coal, but the United
States’ production is rapidly growing and already equals 81.08% of the
British production, and supplies 28.75% of the world’s consumption.

Every subject in this volume is fully discussed, and at the same time
nothing is given which is not appropriate and even necessary. Thus
a combination of completeness and conciseness is reached which is
excellent. Among the most carefully and exhaustively treated subjects
are copper, gold and silver, the platinum group of metals and coal
and iron, though many others might be mentioned, for every subject
undertaken has been thoroughly treated. In the article on copper the
statistics of production and consumption, as well as the condition
of the various domestic and foreign markets, are fully discussed by
the editor, and, in addition, separate articles are also given on
“American Methods of Ore Sampling and Assaying,” by Albert R. Ledoux,
and on “Bessemerizing Copper Matte,” by Charles Wade Stickney. The
article on the statistics of gold and silver is by Mr. R. P. Rothwell,
editor of the volume, and is an excellent piece of statistical work,
giving, as it does, the statistics of production of gold and silver
in the world for a number of years back. To this article are appended
interesting papers on the “Chronology of the Gold and Silver Industry,
1492–1892,” by Walker Renton Ingalls, on “Recent Improvements in Gold
Chlorination,” by John E. Rothwell, and on the “Cyanide Process,” by
Louis Janin, Jr.

The article on the Platinum Group of Metals, by Charles Bullman, gives
complete information regarding the production, consumption, nature of
the deposits, metallurgy and uses of platinum and its related metals,
iridium, rhodium, osmium, palladium and ruthenium. The articles on
Coal and Coke and on Iron and Steel, both by Mr. Wm. B. Phillips, give
full statistics of production and consumption, as well as interesting
historical data, and reports of the condition of various markets. Many
of the other articles in this volume deserve mention, but lack of
space forbids further detail. It may be said, however, that everything
necessary is presented, and nothing unnecessary or unreliable is given;
in other words, the volume contains no trash.

One of the most noticeable features of the volume is the uniform and
systematic manner in which the results are presented. The uniform
arrangement of statistics is a matter requiring the greatest labor
and statistical ability. Compiling a single table of statistics is a
simple matter, but arranging a vast mass of statistics, relating to
many diverse subjects, on a uniform and intelligible basis, is entirely
another matter, and requires the highest skill of the statistician. In
the Mineral Industry this has been accomplished in a most successful
manner; everything is clear and intelligible at the first glance, and
everything is in its proper place. A great detriment to the systematic
presentation of statistics has been, as pointed out by the editor, the
necessity of using our present system of weights and measures, with
“our long and short tons, our barrels of 200, 280, 300 or 400 lbs,
our pounds avoirdupois and our pounds Troy, our bushels of a dozen
different weights, and our gallons of several incomprehensible kinds”;
but the disadvantages of this system have been partly avoided in many
cases by giving the statistics in metric measures as well as in our own.

The question of the cost of production has been given especial
prominence in this volume, with a view to showing the reduction in
the cost of the crude products. To use the words of the editor: “The
itemization of cost is the first essential step in securing economy in
producing any article, and the history of every country and of every
industry has shown that prosperity, whether national, industrial, or
individual, is, in a general way, inversely proportional to the cost
of supplying the rest of the world with what one produces.” These
reductions are in no way dependent on the reduction of wages. On the
contrary, many of the mining industries where the greatest reduction
in cost of production has been accomplished, are carried on with
high priced labor; and in many other cases, where the wages are not
high, the condition of the wage-earners has been greatly improved.
The reduction in cost of production has been entirely brought about
by improvements in mining machinery, by a more thorough understanding
of the nature of the deposits to be worked, and by more intelligent
management and labor. The reduction in cost of production is nowhere
better seen than in the materials most necessary to our welfare. For
instance, coal can in some cases be carried by rail for 400 miles and
delivered on board vessels for from $2 to $2.25 per ton, and yet the
mine owners and railroads make dividends; some of the manufacturing
establishments in Western Pennsylvania obtain coal at from 60 to 75
cents per ton at their works; hard gold-bearing quartz can be crushed,
washed and 95 per cent. of the gold saved on the plates for $1.25
per ton; high grade Bessemer iron ore can be mined, handled, shipped
and delivered a thousand miles from the point of production for less
than $4.00 per ton. All these figures seem almost incredible until
one investigates the various devices which the ingenuity and better
education of those engaged in the industry have invented for reducing
the expenses of production.

The former annual statistical numbers of the Engineering and Mining
Journal were excellent in all they undertook, but the present volume,
the Mineral Industry, makes a great advance in giving the statistics
for foreign countries in addition to those of the United States. By
so doing it gives the American producers an opportunity to know the
present, past and probable future conditions of competition in foreign
countries.

The two most important features in any statistical work are accuracy
and promptness. The necessity of accuracy is self-evident, and without
promptness the statistics lose much of their serviceability to those
most interested in them, for the statistics of an industry published
a year or two years late are rarely of much value to those engaged
in that industry. The business man wants his statistics immediately
after the expiration of the time to which they relate, so that he may
know the existing condition of the industry in which he is engaged;
but if he does not get these statistics until many months or even
several years afterwards, the condition of the industry may have
changed entirely since the time to which the statistics refer. It is
the promptness with which this volume is issued, combined with a high
degree of accuracy, far greater than would be expected in statistics so
hastily compiled, that gives it its especial value.

In conclusion, it may be said, that as a piece of statistical work,
relating to an industry that is world-wide in its scope, combining
accuracy with full detail and systematic arrangement, and issued so
soon after the close of the time to which it relates, the Mineral
Industry has never been equaled in this country or abroad. The former
statistical numbers of the Engineering and Mining Journal, which
referred mostly only to American mining, were considered remarkable
pieces of statistical work, on account of the promptness of their
publication; but in the Mineral Industry we have an epitome of the
mining operations of every quarter of the globe, published almost
immediately after the close of the time to which they refer, a
feat which heretofore would have been declared impossible. This
accomplishment is most creditable to the editor, Mr. Rothwell, to the
systematic organization of the Scientific Publishing Co., and to the
business manager, Mrs. Braeunlich, by whose business ability such an
expensive undertaking is made commercially practicable. The volume will
be found of the greatest value to the economic geologist, the miner,
the engineer and the business man.

                    R. A. F. PENROSE, JR.


FOOTNOTES

   [54] Geological Observations in South America, 1846.

   [55] Beiträge zur Geologie und Paleontologie der argentinischen
        Republik; I. Geologischer Theil, 1885.

   [56] Studien über Cordillerengesteine. Apolda, 1875.

   [57] Reisen in den Cordilleren der argentinischen Republik, Verh.
        der Gesellsch. für Erdkunde. Berlin, 1891.

   [58] Untersuchungen an altkrystallinen Schiefergestenien aus dem
        Gebiete der argentinischen Republik, von B. Kühn. Neues
        Jahrbuch für Min., etc., Beit. Bd. VII., 1891, p. 295.

   [59] Untersuchung argentinischer Pegmatite, etc., von P. Sabersky,
        _ib._, p. 359.

   [60] Untersuchungen an argentinischen Graniten, etc., von J.
        Romberg, _ib._, VIII., pp.




_ANALYTICAL ABSTRACTS OF CURRENT LITERATURE._[61]


  _A New Tæniopteroid Fern and its Allies._ By DAVID WHITE. (Bulletin
      Geological Society of America, 4 pp., 119–122, pl. I.).

Mr. White has described, under the name of _Tæniopteris missouriensis_,
a new and well characterized fern from the Lower Coal-measures in the
vicinity of Clinton, Henry County, Missouri. Botanically, it is of
particular interest in that it combines the so-called tæniopteroid
and alethopteroid types of structure, while geologically it is of
much value in supplying a readily identified stratigraphic mark in a
part of the Carboniferous not especially rich in fossil plants. After
thoroughly describing it and considering its specific and generic
resemblances, the author discusses at length its suggested genetic
relations and represents in a graphic manner a scheme of its probable
ancestors and line of descent.

                    F. H. K.

       *       *       *       *       *

  _Rainfall Types of the United States._ Annual Report by
      Vice-President GENERAL A. W. GREELY. (The National Geographic
      Magazine. Vol. V., April 29, 1893, pp. 45–58 pl. 20).

The paper confines itself to the characteristic distribution of
precipitation throughout the year and gives the rainfall types of the
country.

(a) The best defined type of rainfall within the United States is that
which dominates the Pacific coast region as far east as western Utah.
The characteristic features are a very heavy precipitation during
midwinter, and an almost total absence of rain during the late summer.
(b) The characteristics of the Mexican type, dominating Mexico, New
Mexico and western Texas, are a very heavy precipitation after the
summer solstice and a very dry period after the vernal equinox. August
is the month of greatest rainfall, while February, March and April
are almost free from precipitation. (c) The Missouri type covers the
greatest area, dominating the watersheds of the Arkansas, Missouri and
upper Mississippi rivers, and of lakes Ontario and Michigan. It is
marked by a very light winter precipitation, followed in late spring
and early summer by the major portion of the yearly rain, the period
when it is most beneficial to the growing grain. (d) The Tennessee
type, prevailing in Kentucky, Tennessee, Arkansas, Mississippi and
Alabama, has the highest rainfall the last of winter, while the
minimum is in mid-autumn. (e) The Atlantic type, covering all the
coast save New England, is one where the distribution throughout the
year is nearly uniform, with a maximum precipitation after the summer
solstice, and a minimum during mid-autumn. (f) The St. Lawrence type
is characterized by scarcity during the spring months, heavy rainfall
during the late summer and late autumn months, with a maximum during
November.

The regions lying between these several type-regions have composite
rainfall types, resulting from the influence of two or more simple
types.

                    H. B. K.

       *       *       *       *       *

  _The Geographic Development of the Eastern Part of the Mississippi
      Drainage System._ By LEWIS G. WESTGATE, Middletown, Conn.
      (American Geologist, Vol. XI, April, 1893, 15 pp.)

The drainage of the Eastern Mississippi basin in post-carboniferous
was in all probability consequent upon the tilting which accompanied
the stronger folds of the Appalachian revolution in the east. The
present drainage is found to accord in the main with this hypothetical
post-carboniferous drainage, but several streams depart quite widely
from it.

(a) The great drainage lines of the St. Lawrence basin are structural
valleys developed along the strike of the softer Paleozoic strata, and
at right angles to the original surface. The streams seem, therefore,
to have adjusted themselves to the differences in hardness and
structure of the beds discovered. (b) The Ohio and Cumberland rivers
cut directly across the Tennessee and Cincinnati anticlines. The most
probable explanation is that the rivers were superimposed upon the
arched and eroded Silurian rocks from a thin cover of carboniferous
beds--now entirely removed. (c) The Upper Mississippi does not follow
the dip of the rocks to the southwest, but follows the strike to the
southeast. This part of the river probably dates from the elevation of
the plains on the west and the Appalachians on the east, which marked
the close of the Cretaceous and which left a broad north and south
valley. (d) The author finds good reason to believe that the Lower
Mississippi, in post-carboniferous times, flowed west through Missouri
and Arkansas. The present course was probably taken at the close of
the Cretaceous in consequence of elevations on the west and east, and
possible depression in the south.

The Cretaceous base-level recognized by Davis on the Atlantic slope can
be traced more or less discontinuously, and remnants of it are believed
to exist in Kentucky, Tennessee, Wisconsin, Minnesota and Arkansas. But
in general the work of the Tertiary cycle has obliterated almost all
evidence of it on all but the hard sandstones and conglomerates of the
Paleozoic series.

Good examples of the lowlands excavated from the Cretaceous base-level
during the Tertiary cycle, are the Valley of the East Tennessee and the
central lowland of Kentucky and Tennessee. During the post-Tertiary
sub-cycle the larger streams trenched to greater or less extent these
lowlands. No attempt is made to carry the history of the development
of the Mississippi, drainage into the complicated chapter of the
ice-invasion.

                    H. B. K.

       *       *       *       *       *

  _On a New Order of Gigantic Fossils._ By ERWIN H. BARBOUR. (University
      Studies. Published by the University of Nebraska. Vol. I, No. 4,
      July, 1892, pp. 23, pl. 5).

A part of Sioux County, Nebraska, lying north of the Niobrara River,
has yielded a new order of gigantic Miocene fossils unlike anything
heretofore known. They are best described as fossil corkscrews, of
great size, coiling in right-handed or left-handed curves about an
actual axis or around an imaginary axis. The screws are often attached
at the bottom to an immense transverse piece, rhizome, underground
stem, or whatever it may be, which is sometimes three feet in diameter.
In other cases the corkscrew ends abruptly downward, as it always
does upwards. In still other cases the transverse piece is variously
modified, and sometimes blends into the sandstone matrix, as if the
underground stem, while growing at one end, was decaying at the other.
The fossil corkscrew is invariably vertical, and the so-called rhizome
invariably curves rapidly upwards, and extends outwards an indefinite
distance.

That they could ever have been formed by burrowing animals, by geysers
or springs, or by any mechanical means whatever, is entirely untenable.
Their organic origin is unquestionable. Microscopic sections show
smooth spindle-shaped rods, which are suggestive of sponge spicules.
From the numbers seen in place it is evident that they flourished in
thickly crowded forests of vast extent.

A finely preserved rodent’s skeleton was found in one great stem.
The probable explanation is not that the rodent burrowed there, but
that its submerged skeleton became an anchorage for a living, growing
Daimonelix, which eventually enveloped it.

The author proposes this provisional classification:

  Order.      Family.         Genus.        Species.
         { Daimonelicidæ. { Daimonelix. { circumaxilis
         {                {             { bispiralis
  ------ { -------------- { ----------- { anaxilis
         {                {             { robusta
         {                {             { carinata.
                          { ----------- { ------
                          { ----------- { ------

The different species are described in full.

                    H. B. K.

       *       *       *       *       *

  _The Vertical Relief of the Globe._ By HUGH ROBERT MILL, D.Sc.,
      F.R.S.E. Scottish Geographical Magazine, April, 1890.

The purpose of Dr. Mill’s paper is to show a simple yet adequate
basis on which to build the superstructure of physical geography. It
does not attempt a discussion of the distribution and varieties of
vertical relief. The structure of the earth is stated most simply by
describing it as an irregular stony ball, covered with an ocean and an
envelope of air. If the lithosphere were perfectly smooth and at rest,
with the hydrosphere uniformly spread over its surface, the former
would have the form of the terrestrial spheroid, and the latter would
surround it to a depth of 1.7 miles. The surface of this hypothetical
spheroid Dr. Mill calls _mean sphere level_. Of course, in reality the
surface of the lithosphere is not perfectly smooth. Parts of it are
greatly depressed and parts much elevated, the latter forming the land
of the earth. The writer proceeds to calculate the position of mean
sphere level, and in the absence of accurate data he uses the careful
estimates of Dr. John Murray, which are as follows: Average depths
of oceans = 2.36 miles; average height of land = .426 miles; average
thickness of hydrosphere surrounding smoothed lithosphere = 1.7 mile;
area of land = 55,000,000 square miles; area of oceans = 141,700,000
square miles. Suppose a block of 55,000,000 of square miles area and
1.7 miles deep to be cut out of the smoothed lithosphere and set down
on the surface alongside the depression. No change will take place
in the surface of the hydrosphere. If the surface of the 141,700,000
square miles of lithosphere were reduced to uniformity, the whole
depressed area would lie .66 mile beneath mean sphere level, and
the depth of the ocean becomes 2.36 miles. To raise the land to its
actual mean level above the hydrosphere surface, a sufficient quantity
of matter must be removed from the depressed area and placed on the
elevated block. Let _x_ = the thickness of the belt removed and _y_
equal the thickness of the belt when placed on the elevated block. Then
_x_ + _y_ is the height of the land above the actual hydrosphere level.
From the data given the following equations are easily obtained:

        _x_ + _y_ - .426        =  0
  141.7 _x_       -   55 _y_    =  0
        _x_       = .12 and _y_ = .306 in miles.

The average height of the land above mean sphere level is thus 1.7 +
.306 = 2.006 miles, and the average depth of the depressed portion
beneath mean sphere level is .66 + .12 = .78 mile.

Dr. Mill divides the earth into the three following divisions: (1)
_Abysmal area_, occupying all the depressions beneath the mean surface
of the lithosphere, occupying 50 per cent. of the earth’s surface; (2)
_Transitional area_, comprising all the regions above mean sphere level
covered by the hydrosphere, occupying 22 per cent. of the surface;
(3) _Continental area_, all the lithosphere that projects above the
hydrosphere, or 28 per cent. of the earth’s surface.

                    J. A. B.


FOOTNOTE

   [61] Abstracts in this number are prepared by F. H. Knowlton, Henry B.
        Kummel, J. A. Bownocker.




_ACKNOWLEDGMENTS._


The following papers have been donated to the library of the Geological
Department of the University of Chicago:

ABBOTT, CHARLES C., M.D.

    --Recent Archæological Explorations in the Valley of the Delaware.
    30 pp., 1 pl.--Publications of the University of Pennsylvania.
    Series in Philology, Literature and Archæology, Vol. II, No. 1.

ADAMS, FRANK D.

    --On Some Granites from British Columbia and the Adjacent Parts of
    Alaska and the Yukon District. 14 pp., Ill.--Canadian Record of
    Science, Sept. 1891.

    --Notes to Accompany a Tabulation of the Igneous Rocks based on the
    System of Professor H. Rosenbusch. 6 pp., 1 pl.--Canadian Record of
    Science, Dec. 1891.

    --On the Geology of the St. Clair Tunnel. 8 pp., 1 pl.--Trans. Roy.
    Soc. Canada, Section IV, 1891.

    --On the Presence of Chlorine in Scapolites. 5 pp.--Am. Jour.
    Science, Apr. 1879.

    --Notes on the Lithological Character of some of the Rocks
    Collected in the Yukon District and Adjacent Northern Portion of
    British Columbia. 6 pp.--Annual Report, Geol. Sur. of Canada, 1887.

    --On Some Canadian Rocks Containing Scapolite, with a Few Notes on
    Some Rocks Associated with the Apatite Deposits. 16 pp.--Canadian
    Record of Science, Oct. 1888.

    --On the Microscopical Character of the Ore of the Treadwell Mines,
    Alaska. 5 pp., Ill.--Read before the Royal Soc. Canada, May, 1889.

    --On a Melilite-Bearing Rock (Alnoite) from Ste. Anne de Bellevue,
    near Montreal, Canada. 10 pp., Ill.--Am. Jour. Sci., Vol. XLIII,
    Apr. 1892.

AMI, HENRY M., M.A., F.G.S.

    --The Utica Terrane in Canada. 32 pp.--Canadian Record of Science,
    Oct. 1892.

    --Additional Notes on the Geology and Palæontology of Ottawa and
    its Environs. 11 pp.--Ottawa Naturalist, Sept. 1892.

    --Catalogue of Silurian Fossils from Arisaig, Nova Scotia. 7
    pp.--From the Nova Scotian Inst. of Sci., Ser. 2, Vol. I, 1892.

ANDREAE, A.

    --Ueber die Nachahmung verschiedener Geysirtypen und über
    Gasgeysire. 6 pp.--Gesammt-Sitzung vom 13 Jan. 1893.

BAYLEY, W. S.

    --A Summary of Progress in Mineralogy and Petrography in
    1892.--American Naturalist.

BECKER, GEORGE F.

    --Finite Homogeneous Strain, Flow and Rupture of Rocks. 77
    pp.--Bull. Geol. Soc. Am., Jan. 1893.

BEECHER, C. E.

    --Notice of a New Lower Oriskany Fauna in Columbia Co., N. Y. 4
    pp.--Am. Jour. Sci., Vol. XLIV, Nov. 1892.

BRANNER, J. C.

    --Annual Reports of the Arkansas Geological Survey, 1888, Vols. 1,
    2, 3, 4; 1889, Vol. 2; 1890, Vols. 2 and 3.

BRYCE, GEORGE, LL.D.

    --Older Geology of the Red River and Assiniboine Valleys with an
    Appendix. 7 pp., Ill. Read before the Historical and Scientific
    Society of Manitoba, Nov. 1891.

BROADHEAD, G. C.

    --A Bibliography of the Geology of Missouri, by F. A. Samson. 178
    pp.

    --Report of the Geological Survey of the State of Missouri,
    including Field Work of 1873–4, with 91 illustrations and an atlas.
    788 pp.

    --Preliminary Report on the Coal Deposits of Missouri from Field
    Work prosecuted during the years 1890–91, by Arthur Winslow, State
    Geologist. 220 pp. 1 pl., 131 Illustrations.

CARTER, OSCAR, C. S.

    --Artesian Wells as a Water Supply for Philadelphia. 4 pp.--Proc.
    of the Chem. Section of the Franklin Inst., Jan. 1893.

CHAMBERLIN, T. C.

    --The Requisite and Qualifying Conditions of Artesian Wells. 42 pp.
    1 pl. Extract, Fifth Annual Report of the Director U. S. G. S.

    --Boulder Belts Distinguished from Boulder Trains--Their Origin and
    Significance. 4 pp.--Bull. Geol. Soc. Am. Vol. I., 1879.

    --Some Additional Evidence Bearing on the Interval between the
    Glacial Epochs. 11 pp.--Bull. Geol. Soc. Am., Vol. I., 1890.

    --The Attitude of the Eastern and Central Portions of the United
    States during the Glacial Period. 8 pp.--Am. Geol., Nov. 1891.

    --A Proposed System of Chronologic Cartography on a Physiographic
    Basis. 3 pp.--Bull. Geol. Soc. Am., Vol. II., 1891.

    --(and R. D. SALISBURY.)

    --On the Relationship of the Pleistocene to the Pre-Pleistocene
    Formation of the Mississippi Basin, South of the Limit of
    Glaciation. 17 pp.--Am. Jour. Sci., Vol. XLI., May 1891.

CHANEY, L. W. JR.

    --Cryptozoön Minnesotense in the Shakopee Limestone at Northfield,
    Minn. 3 pp.--Bull. Minn. Acad. Sci., Vol. III., No. 2.

CLARKE, PROFESSOR F. W.

    --A Number of Pamphlets by Different Authors; 5 Volumes of the
    Hayden Survey of the Territories.

COOKE, J. H.

    --Geological Notes on Gozo. 6 pp.--Geol. Mag., Aug. 1891.

    --Notes on Stereodon Melitensis, Owen. 2 pp.--Geol. Mag., Dec. 1891.

    --On the Occurrence of a Black Limestone in the Strata of the
    Maltese Islands. 3 pp.--Geol. Mag., Aug. 1892.

    --The Mediterranean Naturalist. From Aug. 1, 1891, to Sept. 1,
    1892, inclusive.

CROSBY, W. O.

    --Notes on the Physical Geography and Geology of Trinidad. 11
    pp.--Proc. Boston Soc. Nat. Hist., Oct. 1888.

    --On the Joint Structure of Rocks. 5 pp.

    --On a Possible Origin of Petrosilicious Rocks. 9 pp.--Proc. Boston
    Soc. Nat. Hist., March 1879.

    --On the Classification of the Textures and Structures of Rocks. 9
    pp.--Proc. Boston Soc. Nat. Hist., Nov. 1881.

    --On the Elevated Reefs of Cuba. 6 pp.--Proc. Boston Soc. Nat.
    Hist., June 1883.

    --On the Chasm called “Purgatory,” in Sutton, Mass. 2 pp.--Proc.
    Boston Soc. Nat. Hist., Oct. 1883.

    --Origin of Continents. 11 pp.--Geol. Mag., June 1883.

    --On the Relationship of the Conglomerate and Slate in the Boston
    Basin. 20 pp.--Proc. Boston Soc. Nat. Hist., Jan. 1884.

    --Quartzites and Siliceous Concretions. 10 pp.--Technology
    Quarterly, May, 1888.

    --Relations of the Pimite of the Boston Basin to the Felsite and
    Conglomerate. 14 pp.--Technology Quarterly, Feb. 1889.

    --The Madison Bowlder. 9 pp., 1 pl.--Appalachia, Vol. VI, No. 1.

    --On the Contrast in Color of the Soils of High and Low Latitudes.
    10 pp.

    --Geology of the Outer Islands of Boston Harbor. 8 pp.--Proc.
    Boston Soc. Nat. Hist., 1888.

    --Physical History of the Boston Basin. 22 pp.--Lectures to
    Teachers’ School of Science, 1889–90.

    --The Kaolin in Blandford, Mass. 9 pp.--Technology Quarterly, Aug.
    1890.

    --Composition of the Till or Boulder-Clay. 25 pp.--Proc. Boston
    Soc. Nat. Hist., Vol. XXV, 1890.

    --Geology of Hingham, Mass. 12 pp., 3 maps.--Proc. Boston Soc. Nat.
    Hist., Vol. XXV, May, 1892.

    --Geology of the Black Hills of Dakota. 29 pp.--Proc. Boston Soc.
    Nat. Hist., Vol. XXIII.

CULVER, G. E.

    --On a Little Known Region of Northwestern Montana. 18 pp., 1
    pl.--Wis. Acad. Sci., Arts and Letters, Dec. 1891.

DARTON, N. H.

    --The Relations of the Traps of the Newark System in the New Jersey
    Region. 82 pp., 1 map, 4 pl.--Bull. U. S. G. S.

    --On Fossils in the Lafayette Formation in Virginia. 3 pp.--Am.
    Geol., March, 1892.

DERBY, O. A.

    --On Nepheline Rocks in Brazil. 15 pp., Ill.--Quart. Jour. Geol.
    Soc., 1891.

DOUGLAS, JAMES.

    --Biographical Sketch of Thomas Sterry Hunt. 11 pp.--Trans. Am.
    Inst. Min. Engin.

EYERMAN, JOHN.

    --Notes on Geology and Mineralogy. 4 pp.--Proc. Acad. Nat. Sci.,
    Phila., 1889.

    --The Mineralogy of Pennsylvania, Part I. 54 pp.

    --Bibliography of North American Vertebrate Paleontology for the
    year 1889. 4 pp.--Am. Geol., 1890.

    --Bibliography of North American Vertebrate Paleontology for the
    year 1890. 8 pp.--Am. Geol., 1891.

    --On the Mineralogy of the French Creek Mines in Pennsylvania. 4
    pp.--N. Y. Acad. Sci., 1889.

    --A Catalogue of the Paleontological Publications of Joseph Leidy,
    M.D., LL.D. 10 pp.--Am. Geol., Nov. 1891.

    --Bibliography of North American Vertebrate Paleontology for the
    year 1891. 8 pp.--Am. Geol., April, 1892.

FELIX, JOHANNES.

    --Untersuchungen ueber fossile Hölzer. 12 pp., 1 pl.--Abdruck a. d.
    Zeitschr. Deutschen geolog. Gesell., 1887.

    --Beiträge zur Kenntniss der Gattung Protosphyraena Leidy. 24 pp.,
    3 pl.--Aus der Zeitschr. Deutschen geolog. Gesell., 1890.

    --Ueber die tektonischen Verhältnisseder Republik Mexiko. 20 pp., 2
    pl.--Aus der Zeitschr. Deutschen geolog. Gesell., 1892.

FERRIER, W. F.

    --Rapport Géologique. Rapport des Opérations de 1866 à 1869. 530
    pp., with maps.

    --Descriptive Sketch of the Physical Geography and Geology of the
    Dominion of Canada, by Alfred R. C. Selwyn and G. M. Dawson. 55 pp.
    1884.

    --List of Publications of the Geological and Natural History Survey
    of Canada. 36 pp.

    --Geological and Natural History Survey and Museum of
    Canada.--Report of Progress, 1882–83–84. Annual Report for 1888–89.

FISHER, REV. O.

    --The Hypothesis of a Liquid Condition of the Earth’s Interior
    considered in Connection with Professor Darwin’s Theory of the
    Genesis of the Moon. 14 pp.--Proc. Cambridge Phil. Soc., 1892.

GILBERT, G. K.

    --Continental Problems. Annual Address by the President of the
    Geological Society of America. 12 pp., Ill.--Bull. Geol. Soc. Am.,
    1893.

    --The Moon’s Face. A Study of the Origin of its Features. 52 pp., 1
    pl.--Phil. Soc. Washington, 1893.

DEGEER, BARON GERARD.

    (The following pamphlets are in the Swedish language, the titles
    being translated):

    --On the Occurrence of Hydrous Manganese Oxide between the Pebbles
    of the Osar at Upsala. 4 pp.--Aftryck ur Geol. Föreningens i
    Stockholm Förhandl., 1882.

    --On Actinocamax Quadratus. 3 pp.--Ibid. Bd. VII.

    --On Kaolin and other Minerals, derived from decayed Archaean rocks
    in the Cretaceous near Kristianstad. 8 pp.--Ibid. Bd. VII.

    --Discussion of the Conglomerate at Vestani in Scania. 5 pp.--Ibid.
    1886.

    --On Folded Veins in Archaean Rocks. 5 pp.--Ibid. 1887.

    --On Windworn Stones. 20 pp.--Ibid. 1887.

    --On the Cave of Barnakoella, a new exposure of the Cretaceous in
    Scania (in Southern Sweden). 22 pp.

    --On the Earlier Baltic Ice-Stream in Eastern Scania. 4 pp.--Ibid.
    Bd. X.

    --Description of the Map sections Vidtskoefle, Karlshamn (Scanian
    part), and Soelvsborg (Scanian part). 88 pp. 1889.

    --Description of the Map section Baeckaskog. 110 pp. 2 pl., 1 map,
    1889.

    --On the Situation of the Ice Shed during the two Glaciations of
    Scandinavia. 20 pp. 1889.

    --On the Quaternary Changes of Level in Scandinavia. 66 pp. 1
    map.--Ibid. 1888–90.

    --On a Series of Small Dump Moraines near Stockholm, probably
    marking the annual recession of the Ice Border. 3 pp.--Ibid. Dec.
    1889.

    --On the Relation between the Carbonates of Lime and Magnesia in
    Limestones (Cretaceous and Silurian). 4 pp.--Ibid. 1889.

    --On the Origin of the Lakes in Eastern Scania. 4 pp.--Ibid. Jan.
    1889.

    --On the Latest Investigations of the Terminal Moraines South of
    the Baltic. 4 pp.--Ibid. April, 1889.

    --On Continental Changes of Level in Scandinavia and North America.
    4 pp.--Ibid. Feb. 1892.

    --Ueber ein Conglomerat im Urgebirge bei Vestana in Schonen.
    28 pp. 1 pl. (German Uebersetzt von Felix Wahnschaffe in
    Berlin).--Zeitschr. d. Deutschen geolog. Gesell. 1886.

    --Quaternary Changes of Level in Scandinavia (English). 4 pp., 1
    map.--Bull. Geol. Soc. Am., Vol. 3, 1891.

    --On Pleistocene Changes of Level in Eastern North America. 22 pp.,
    1 map (English).--Proc. Bost. Soc. Nat. Hist., 1892.

HALL, C. W.

    --The Deep Well at Minneopa, Minnesota. 3 pp.--Bull. Minn. Acad.
    Nat. Sci., Vol. III., No. 2.

HALLOCK, WILLIAM.

    --Preliminary Report of Observations at the Deep Well at Wheeling,
    W. Va. 3 pp.--Proc. A. A. A. S. 1891.

    --(and F. Kohlrausch.)

    --Ueber den Polabstand, den Inductions--und Temperatur--Coefficient
    eines Magnetes und ueber die Bestimmung von Trägheitsmomenten durch
    Bifilarsuspension. 20 pp.--Nachrichten Koenigliche Gesellschaft der
    Wissenschaften, 1883.

HATCHER, J. B.

    --The Titanotherium Beds. 18 pp., Ill.--Am. Naturalist. 1893.

    --The Ceratops Beds of Converse County, Wyoming. 10 pp.--Am. Jour.
    Sci. Feb. 1893.

HAY, O. P., PH.D.

    --The Northern Limits of the Mesozoic Rocks in Arkansas. 30
    pp.--Annual Report Geol. Surv. Ark. 1888.

HOBBS, WM. H.

    --Secondary Banding in Gneiss. 6 pp. 1 pl., Ill.--Bull. Geol. Soc.
    Am., 1891.

    --Notes on a Trip to the Lipari Islands. 12 pp. 1 pl., Ill.--Wis.
    Acad. Sci., 1892.

    --On Intergrowths of Hornblende with Augite in Crystalline Rocks. 1
    p.--Science, Dec. 23, 1892.

    --Phases in the Metamorphism of the Schists of Southern Berkshire.
    12 pp. 1 pl., Ill.--Bull. Geol. Soc. Am., Feb. 1893.

HOLMES, W. H.

    --Geology of the Elk Mountains, Col. (1874.)

    --Geology of Southwestern Colorado. (1875.)

    --Geology of the Yellowstone Park. (1880.)

HOLST, N. O.

    --Matricit och Marmairolit, tvaenne nya Mineralier fran Vermland. 5
    pp.--Aftryck ur Geologiska Föreningens i Stockholm Förhandlingar,
    1875.

    --Om de glaciala rullstensasårne. 16 pp.--Ibid., 1876.

    --Klotdiorit fran Slättmossa, Järeda socken, Kalmar län. 10 pp. 1
    pl.--Ibid., Bd. VII.

    --Om Ett Fynd af Uroxe i Rakneby, Ryssby Sockenk Kalmar län. 21 pp.
    2 pl.--Ibid., Bd. X, 1888.

    --Hvem fann den norrlandska andesiten? 6 pp. Ibid.--Bd. X, 1888.

    --Om en Mäktig qvarsit, yngre än olenus-skiffer. 3 pp.--Ibid. Bd.
    XI, 1889.

    --Om en nyupptäckt fauna i block af kambrisk sandsten, insamlade af
    dr N. O. Holst af Joh. Chr. Moberg. 18 pp. 1 pl.--Ibid., Bd. XIV,
    1892.

    --Bidrag till Kännedomen om Lagerföldjen inom den Kambriska
    Sandstenen. 17 pp.

    --Ryoliten vid Sjoen Mien. 52 pp. 1 pl., Ill.

    --Berättelse om en ar 1880, i Geologiskt Syfte Foretagen Resa Till
    Groenland. 74 pp. 1 map, 1880.

HOVEY, EDMUND OTIS.

    --Observations on some of the Trap Ridges of the
    East-Haven--Branford, (Ct.) Region. 23 pp. 1 pl.--Am. Jour. Sci.,
    Nov. 1889.

HYATT, ALPHEUS.

    --Remarks on the Pinnidae. 12 pp.

    --Jura and Trias at Taylorville, California. 18 pp.--Bull. Geol.
    Soc. Am., Vol. III, 1892.

IDDINGS, J. P.

    --Obsidian Cliff, Yellowstone National Park. 48 pp. 9 pl., 1888.
    7th Annual Rept. U. S. G. S.

    --On the Crystallization of Igneous Rocks. 50 pp.--Phil. Soc.
    Washington, Vol. XI, 1889.

    --On a Group of Volcanic Rocks from the Tewan Mountains, New
    Mexico, and on the Occurrence of Primary Quartz in certain Basalts.
    32 pp.--Bull. U. S. G. S., No. 66.

    --Spherulitic Crystallization. 18 pp. 2 pl.--Bull. Phil. Soc.
    Washington, Vol. XI, 1891.

    --The Origin of Igneous Rocks. 124 pp. 1 pl.--Bull. Phil. Soc.
    Washington, Vol. XII, May, 1892.

JAMES, JOS. F.

    --Manual of the Paleontology of the Cincinnati Group. 16 pp.,
    Ill.--Cincinnati Soc. Nat. Hist., Oct. 1892, Jan. 1893.

JIMBO, K.

    --General Geological Sketch of Hokkaido, with special reference to
    the Petrography.

JUDD, PROF. J. W.

    --A Problem for Cheshire Geologists. 5 pp.--Proc. Chester Soc. Nat.
    Sci., 1884.

    --On Krakatoa. 4 pp. 1884.

    --Address to the Geological Section of the British Association.
    1885. 20 pp.

    --On Marekanite and its Allies. 8 pp.--Geol. Mag., June, 1886.

    --Address delivered at the Anniversary Meeting of the Geological
    Society of London. Feb. 18, 1887, 57 pp. Feb. 17, 1888, 56 pp.

    --On a Cetacean from the Lower Oligocene of Hampshire. 6 pp.,
    Ill.--Quart. Jour. Geol. Soc., Nov., 1881.

    --On the Gabbros, Dolerites, and Basalts of Tertiary Age, in
    Scotland and Ireland. 49 pp., 4 pl.--Ibid., Feb., 1886.

    --The Tertiary Volcanoes of the Western Isles of Scotland. 32
    pp.--Ibid., May, 1889.

    --On the Growth of Crystals in Igneous Rocks after their
    Consolidation. 10 pp., 1 pl.--Ibid., May, 1889.

    --The Propylites of the Western Isles of Scotland and their
    Relation to the Andesites and Diorites of the District. 44 pp., 2
    pl.--Quart. Jour. Geolog. Soc., Aug., 1890.

    --On the Relation of the Reptiliferous Sandstone of Elgin to the
    Upper Old Red Sandstone. 10 pp.--Proc. Royal Soc., No. 241, 1885.

    --On the Relations between the Solution-Planes of Crystals and
    those of Secondary Twinning, and on the Mode of Development of
    Negative Crystals along the Former. 12 pp., 1 pl.--Mineralogical
    Magazine.

    --On the Development of a Lamellar Structure in Quartz-Crystals by
    Mechanical means. 9 pp., 1 pl.--Ibid.

    --On the Relations between the Gliding Planes and the Solution
    Planes of Augite. 5 pp. 1890.

    --Chemical Changes in Rocks under Mechanical Stresses. 22
    pp.--Journal of the Chemical Society, May, 1890.

    --The Rejuvenescence of Crystals. 8 pp.--Royal Institute, 1891.

KEITH, ARTHUR.

    --Geology of Chilhowee Mountain in Tennessee. 18 pp., 1 pl.--Bull.
    Phil. Soc., Washington, Vol. XII., pp. 71–88. 1892.

    --The Structure of the Blue Ridge, near Harper’s Ferry. 10 pp., 2
    pl.

KNOWLTON, F. H.

    --Bread-Fruit Trees in North America.--Science, Jan. 13, 1893.

LAWSON, A. C.

    --Geology of the Rainy Lake Region, with Remarks on the
    Classification of the Crystalline Rocks west of Lake Superior. 8
    pp.--Am. Jour. Sci., June, 1887.

    --Notes on Some Diabase Dykes of the Rainy Lake Region. 14 pp., Ill.

    --Notes on the Occurrence of Native Copper in the Animikie Rocks of
    Thunder Bay. 5 pp.--Am. Geol., March, 1890.

    --Notes on the Pre-Paleozoic Surface of the Archean Terranes of
    Canada. The Internal Relations and Taxonomy of the Archean of
    Central Canada. 32 pp.--Bull. Geol. Soc. Am., 1890.

    --Petrographical Differentiation of Certain Dykes of the Rainy Lake
    Region.

LINDGREN, WALDEMAR.

    --Petrographical Notes from Baja, California, Mexico. 17 pp.--Proc.
    Cal. Acad. Sci., 2d Ser. II. (1889), 9 pp. Vol. III. (1890).

    --Eruptive Rocks from Montana. 18 pp.--Ibid., Vol. III.

    --The Silver Mines of Calico, California. 18 pp., 1 pl.--Trans. Am.
    Inst. Min. Engin.

    --The Gold Deposit at Pine Hill, California. 6 pp.--Am. Jour. Sci.,
    Aug., 1892.

    --A Sodalite-Syenite and other Rocks from Montana; with Analysis,
    by W. H. Melville. 12 pp.--Ibid., April, 1893.

    --Contributions to the Mineralogy of the Pacific Coast, by W. H.
    Melville and W. Lindgren. 32 pp., 3 pl.--Bull. U. S. G. S., 1890,
    No. 61.

LYMAN, BENJAMIN SMITH.

    --Shippen and Wetherill Tract. 36 pp., with map.

MARTIN, F. W.

    --The Boulders of the Midland District. 22 pp., with map.--Proc.
    Birmingham Phil. Soc., Vol. VII., Part I.

    --First Report upon the Distribution of Boulders in South
    Shropshire and South Staffordshire. 25 pp.--Ibid., Vol. VI., Pt. I.

MARSH, O. C.

    --Restoration of Claosaurus and Ceratosaurus. Restoration of
    Mastodon Americanus. 8 pp., 3 pl.--Am. Jour. Sci., Oct., 1892.

    --Restoration of Anchisaurus. 2 pp., 1 pl.--Ibid., Feb., 1893.

MERRIMAN, MANSFIELD.

    --The Strength and Weathering Qualities of Roofing Slates. 19 pp.,
    3 pl.--Am. Soc. Civil Engin., Sept., 1892.

MILL, HUGH ROBERT.

    --On the Physical Conditions of the Water in the Clyde Sea-Area. 25
    pp., 1 pl.--Phil. Soc. Glasgow, 1887.

    --Configuration of the Clyde Sea-Area. 7 pp. 1 pl.--Scott. Geog.
    Mag., Jan., 1887.

    --Recent Physical Research in the North Sea. 14 pp. with
    map.--Ibid., Aug., 1887.

    --The Relations between Commerce and Geography. 13 pp.--Ibid.,
    Dec., 1887.

    --Sea Temperatures on the Continental Shelf. 6 pp.--Ibid., Oct.,
    1888.

    --Scientific Earth-Knowledge as an Aid to Commerce. 18 pp.--Ibid.,
    June, 1889.

    --Statical Oceanography--a Review. 7 pp.--Ibid., May, 1891.

    --The Principles of Geography. 7 pp.--Ibid., Feb., 1892.

    --On the Physical Conditions of the Water in the Firth of Forth. 6
    pp., 4 pl.--Appendix to 5th Annual Report of the Fishery Board for
    Scotland.

    --Report of Physical Observations on the Sea to the West of Lewes,
    during July and August, 1887. 26 pp., 1 pl.--Ibid., 6th Annual.

    --Report on a Physical and Chemical Examination of the Water in the
    Moray Firth and the Firths of Inverness, Cromarty, and Dornoch. 36
    pp., 4 pl.--Ibid.

    --Report on the Apparatus required for carrying on Physical
    Observations in connection with the Fisheries. 4 pp., 2 pl.--Ibid.

    --Report on the Physical Observations carried on by the Fishery
    Board for Scotland in the Firths of Forth and Tay and in the Clyde
    Sea-Area. 35 pp., 2 pl.--Ibid., Ninth Annual, Part III.

    --River Entrances. 12 pp.--Supplem. Paper, Roy. Geog. Soc., Vol.
    II., Part III.

    --Marine Temperature Observations. 9 pp.--Quart. Jour. Royal Met.
    Soc.

    --On the Tidal Variation of Salinity and Temperature in the Estuary
    of the Forth. 10 pp. 1 pl.--Proc. Royal Soc. Edin., 1885–6.

    --The Salinity and Temperature of the Moray Firth, and the Firths
    of Inverness, Cromarty, and Dornoch. 12 pp., 1 pl.--Ibid., 1887.

    --On the Mean Level of the Surface of the Solid Earth. 4
    pp.--Ibid., 1889–90.

    --The Clyde Sea-Area. 88 pp., 12 plates and maps.

    --Contributions to Marine Meteorology Resulting from the Three
    Years’ Work of the Scottish Marine Station. 8 pp.

    --Observations of Sea Temperature, made by Staff of the Scottish
    Marine Station between 1884 and 1887. 64 pp.

    --Fourth and Final Report of the Committee appointed to arrange an
    Investigation of the Seasonal Variations of Temperature in Lakes,
    Rivers, and Estuaries. 52 pp., 1 pl.--British A. A. S., 1891.

OSBORN, HENRY F., SC.D.

    --A Memoir upon Loxolophodon and Uintatherium, Accompanied by a
    Stratigraphical Report of the Bridger Beds in the Washakie Basin,
    by John Bach McMaster, C. E. 54 pp., 6 pl.--Contributions from
    the E. M. Museum of Geology and Archæology of the College of New
    Jersey, July, 1881.

PENCK, ALBRECHT

    --Ueber Palagonit und Basaltuffe. 74 pp.--Ibid., 1879.

    --Ueber einige Kontaktgesteine les Kristiania-Silurbeckens. 20
    pp.--Magazin for Naturvidenskaferne, 1879.

    --Studien über lockere vulkanische Answürflinge. 33 pp., 1 pl.--a.
    d. Zeitschr. d. Deutsch. Geolog. Gesellschaft, 1878.

    --Bericht über eine gemeinsame Excursion in den Böhmerwald. 10
    pp.--Ibid., 1887.

    --Erläuterungen zur geologischen Specialkarte des Königreichs
    Sachsen. Section Colditz. 59 pp., 1879.

    --Glaciers of the Isar and the Linth. 8 pp. Geol. Mag., June, 1886.

    --Die Deutschen Küsten. 9 pp.

    --Ziele der Erdkunde im Oesterreich. 16 pp.

    --Theorien über das Gleichgewicht der Erdkruste. 26 pp., 1889.

    --Das Endziel der Erosion und Denudation. 12 pp.--a. d.
    Verhandlungen des VIII Deutschen Geographentages zu Berlin. 1889.

    --Der Flöcheninhalt der österreichisch-ungarischen Monarchie. 6
    pp.--a. d. Sitzungsberichten der Kais. Akademie d. Wissenschaften
    in Wien. 1889.

    --Die Glacialschotter in den Ostalpen. 21 pp.--Verlag des d. u. Oe.
    Alpenvereins.

    --Die Geographie an der Wiener Universität. 16 pp.--a. d. Geog.
    Abhandlungen.

    --Die Donau. 101 pp., 2 pl.--Vorträge des Vereines zur Verbreitung
    naturwissenschaftlicher Kenntnisse in Wien. 1891.

    --Ueber die Herstellung einer Erdkarte im Mass-stabe von 1:1000000.
    30 pp.--Deutsche Geog. Blätter Bd. XV, h. 3 u. 4.

    --Bericht über die Ausstellung des IX Deutschen Geographentages zu
    Wein. 1891. 144 pp.

    --Der neunte deutsche Geographentag in Wien. 24 pp.--aus
    Oesterr-Ungar. Revue, 1891.

    --Die Formen der Landoberfläche. 10 pp.--a. d. Verhandlungen des IX
    d. Geographentages in Wien. 1891.

    --Das Studium der Geographie. 15 pp.--a. d. XVII Jahresberichte des
    Vereines der Geographen an der Universität Wien.

PROSSER, CHARLES S.

    --Notes on the Geology of Skunnemunk Mountain, Orange County, N. Y.
    18 pp.--Trans. N. Y. Acad. Sci., June, 1892.

RUSSELL, I. C.

    --On the Former Extent of the Triassic Formation of the Atlantic
    States. 10 pp.--Am. Naturalist, Oct., 1880.

    --The Physical History of the Triassic Formation of New Jersey and
    the Connecticut Valley. 35 pp.--N. Y. Acad. Sci., 1878, pp. 220–254.

SIEGER, DR. ROBERT.

    --Die Schwankungen der Hocharmenischen Seen seit 1800 in
    vergleichung mit einigen verwandten Erscheinungen. 80 pp., 1 pl.

SOLLAS, W. J. B. A., F. G. S.

    --On the Perforate Character of the Genus Webbina, 4 pp., 1 pl.

    --On the Silurian District of Rhymney and Pen-y-lan, Cardiff, 32
    pp., 1 pl.--Quart. Jour. Geol. Soc. 1879.

    --On Astroconia Granti, from the Silurian Formation of Canada, 6
    pp. Ill.--Ibid. May 1881.

    --On a New Species of Plesiosaurus from the Lower Lias of
    Charmouth, 44 pp., 2 pl.

    --On the Origin of Freshwater Faunas: A Study in Evolution, 3
    pp.--Sci. Proc., Royal Dublin Soc. 1884.

    --The “Coecal Processes” of the Shells of Brachiopods interpreted
    as Sense Organs, 3 pp.--Ibid., Nov. 18, 1885.

    --A Contribution to the History of Flints, 5 pp.--Ibid., Dec. 14,
    1887.

    --On Homotoechus (Archæocidaris Harteana, Baily) A new Genus of
    Palaeozoic Echinoids, 3 pp.--Ibid., June 17, 1891.

    --On the Structure and Origin of the Quartzite Rocks in the
    Neighborhood of Dublin, 20 pp., 1 pl., Ill.--Ibid., Feb. 17, 1892.

    --On the Variolite and Associated Igneous Rocks of Round Wood Co.
    Wicklow, 22 pp. Ill.--Ibid., March 25, 1893.

    --On Pitchstone and Andesite from Tertiary Dykes in Donegal. 7 pp.
    Ill.--Ibid., March 25, 1893.

    --On the Occurrence of Zinnwaldite in the Granite of the Mourne
    Mountains, 2 pp.--Proc. Royal Irish Acad. 1890. 3d Ser. Vol. 1; No.
    3.

STEENSTRUP, J. JAPETUS S. M.

    --Sur les Kjokkenmoddings de l’Age de la Pierre et sur la Faune
    et la Flore Préhistoriques de Danmark. 40 pp., 2 pl. Ill.--Bull.
    Congrés International d’Archéologie Préhistorique à Copenhague,
    1869.

    --Torvemosernes Bidrag til Kundskab om Danmark’s forhistorische
    Natur og Kultur, 42 pp.

    --Die Mammuthjäger-Station bei Predmost im oesterreichischen
    Kronlande Mähren. 31 pp.--Mittheil. der Anthropologischen Gesell.,
    in Wien, 1890.

    --Hvorledes dannes de store Isfjaelde? 7 pp.--Saertryk af
    “Geografisk Tidskrift.”

STEINMANN, G.

    --Die Moränen am Ausgange des Wehrathals, 6 pp. Ill.--a. d. Bericht
    über die XXV. Versammlung des Oberrheinischen geolog. Vereins Zu
    Basel.

    --Die Moränen am Ausgange des Wehrathals, 5 pp.--Ibid.

    --Bemerkungen über die tektonischen Beziehungen der oberrheinischen
    Tiefebene zu dem nordschweizerischen Kettenjura, 10 pp. Ill.--a. d.
    Berichte der Naturforschenden Gesell. zu Freiberg.

    --Ueber die Ergebnisse der neueren Forschungen im Pleistocän des
    Rheinthals, 4 pp.--a. d. Zeitschs. d. Deutschen geolog. Gesell.
    1892.

TAYLOR, W. EDGAR.

    --The Ophidia of Nebraska, 48 pp.

THOMASSEN, T. CH.

    --Jordskjaelv i Norge 1888–1890. Anhang: Deutsches Resumè und
    tabellarische Zusammenstellung der in 1880–1890 eingetroffenen
    Erdbeben, 56 pp., 2 pl.

    --Berichte über die, wesentlich seit 1834, in Norwegen
    eingetroffenen Erdbeben, 52 pp.--a. Bergens Museums Aarsberetning
    1888.

U. S. GEOLOGICAL SURVEY.

    --Annual Reports of the Director, 4th to 11th.

    --Monographes, XVII, XVIII, XX.

    --Mineral Resources of the United States, 6 vols. 1883 to 1890.

    --Bulletins 30, 56, 65, 66, 69, 70 to 84 incl.

U. S. COAST AND GEODETIC SURVEY.

    --Report U. S. Coast Survey, 34 Volumes, Charts.

VAN HISE, C. H.

    --Bulletin 86 U. S. G. S. Correlation Papers--Archæan and
    Algonkian. 549 pp., 12 pl.

WALCOTT, C. D.

    --Notes on the Cambrian Rocks of Pennsylvania and Maryland, from
    the Susquehanna to the Potomac. 14 pp.--Am. Jour. Sci. Dec. 1892.

WAHNSCHAFFE, FELIX.

    --Bericht ueber den von der geologischen Gesellschaft in Lille
    veranstalteten Ausflug in das Quartärgebiet des nordlichen
    Frankreich und des Südlichen Belgien, 12 pp.--Jahrbuch der Königl.
    preuss. geolog. Landesanstalt für 1891.

WARRING, C. B., PH. D.

    --Geological Climate in High Latitudes, 16 pp.--Popular Sci.
    Monthly, July, 1886.

WESTGATE, LEWIS G.

    --The Geographic Development of the Eastern Part of the Mississippi
    Drainage System, 16 pp. Am. Geol. April 1893.

WINCHELL, H. V.

    --The Mesabi Iron Range in Minnesota, 72 pp., 5 pl.--20th annual
    Report. Minn. Geol. Survey, 1891.

WINCHELL, N. H.

    --The Crystalline Rocks, Some Preliminary Considerations as to
    their Structures and Origin, 28 pp.--20th Annual Report, Minn.
    Geol. Survey, 1891.

WOODWORTH, J. B.

    --The Ice Wall on the Beach at Hull, Mass., January,
    1893.--Science. Feb. 10, 1893.


(_Further acknowledgments of pamphlets already received will be made in
the next number._)




Transcriber’s Notes


Punctuation, hyphenation, and spelling were made consistent when a
predominant preference was found in the original book; otherwise they
were not changed.

Simple (and frequent) typographical errors were corrected; unbalanced
quotation marks were remedied when the change was obvious, and
otherwise left unbalanced.

Footnotes have been sequentially renumbered to make them unique, and
then moved to the ends of the articles to which they belong.

Illustrations and references to them have been sequentially renumbered.

Pages 344, 345: Text shown as =a=, =b=, and =c= was printed in a
Blackletter font.

Footnote 30, originally on page 368: The page range was printed as
shown (with dashed placeholders); the missing numbers may be 369 and
370.

Footnote 46, originally on page 382: The citation for “Proc. Bos. Soc.
Nat. Hist.” had no further details.

Page 411: Text uses both “Schiefergesteinen” and “Schiefergestenien”.

Footnote 60, originally Footnote 7 on page 411, omitted the page number
reference.





End of Project Gutenberg's The Journal of Geology, Vol. I. No. 3, by Various