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                              EXPERIMENTS
                                  AND
                              OBSERVATIONS

                       TENDING TO ILLUSTRATE THE
                                 NATURE
                                  AND
                               PROPERTIES
                                   OF
                              ELECTRICITY.

           In one LETTER to _Martin Folkes_, Esq; President,
                    and Two to the _Royal Society_.


                     By _WILLIAM WATSON_, F. R. S.


                               _LONDON_:

              Printed for C. DAVIS, Printer to the _Royal
                Society_, against _Gray's-Inn, Holborn_.

                               MDCCXLVI.

                         [Price One Shilling.]




                                  THE
                                PREFACE.


_The following Sheets were not intended to be made publick, but as part
of the Philosophical Transactions. As those Works are printed in the
order of Time they are read; these Observations, communicated to the_
ROYAL SOCIETY _at different Meetings, would, upon that Account, have
been publish'd separate in different Numbers of those Transactions. To
satisfy therefore the Impatience of several learned and very valuable
Friends, to whose Importunities I have neither Will, nor Inclination to
deny any thing in my Power to grant, I caused a few Copies to be
printed, that the whole might be seen together, and then broke up the
Press. This has excited the Curiosity of the Publick, and raised a
Demand for these Experiments much beyond what I had reason to expect. I
therefore found it necessary to send them to the Press a second Time,
lest some of those over-officious Gentlemen, who are always ready on
these Occasions, should do it for me; so that whoever has an
Inclination, may now be made acquainted, by what Means the several
surprizing Phænomena of Electricity have been brought about._

_I chose to lay these Papers before the Publick in the same Dress
wherein they appeared before the very honourable and learned Body, to
whom, as the various Effects of Electricity presented themselves, they
were regularly communicated, and from whom they met with a very
favourable Reception. Many Members of the_ ROYAL SOCIETY, _as well as
several other Persons of great Rank and Quality, have been repeated
Witnesses of the Facts which are here laid before the World;
particularly the present worthy President_, MARTIN FOLKES, Esq; _whose
extensive Abilities and great Knowledge in every Branch of useful
Literature are exceeded only by his Candour and Zeal in promoting
Science. The Advice and Assistance of this Gentleman, whose Friendship I
shall always esteem as one of the greatest Happinesses of my Life, has
been of great Moment in the Prosecution of these Discoveries. I
therefore take this publick Manner of testifying my sincerest
Obligations as well to him, as to Sir_ HANS SLOANE, Bart. _who, although
retired from Business, is nevertheless attentive to whatever tends to
the Advancement of Philosophy. Upon a Report made to him of these
Experiments and Observations, he, as surviving Executor of Sir_ GODFREY
COPLEY, _was pleased to appoint me last Year to receive the annual
Prize-medal of Gold, given by the_ ROYAL SOCIETY _in consequence of Sir_
GODFREY'S _Benefaction. The Honour of being so particularly taken notice
of by Gentlemen of such distinguished Merit, as it cannot but give me
the highest Pleasure, so shall it ever continue to raise in me
Sentiments of the truest Gratitude, and most profound Respect._

_IF it should be asked, to what useful Purposes the Effects of
Electricity can be applied, it may be answered, that we are not as yet
so far advanced in these Discoveries as to render them conducive to the
Service of Mankind. Perfection in any Branch of Philosophy is to be
attained but by slow Gradations. It is our Duty to be still going
forward; the rest we must leave to the Direction of that Providence,
which we know assuredly, has created nothing in vain. But I make no
Scruple to assert, that notwithstanding the great Advances, which have
been made in this part of natural Philosophy within these few Years,
many and great Properties remain still undiscover'd. Future Philosophers
(some perhaps even of the present Age) may deduce from electrical
Experiments, Uses extremely beneficial to Society in general._

_NO present Advantage accrued to those Persons, or to that Age, which
first discover'd the Properties of the Magnet. Many hundreds of Years
intervened, before they were applied to the great Uses of Navigation.
Had these remain'd a secret till now, what other Methods could have been
substituted in their Place, by which we could securely traverse the vast
Ocean? All the Advantages we receive from distant Commerce, we must
still have been Strangers to, but for this fortunate Application of the
magnetical Power. And even the Discoveries thus far had been very
imperfect, without the Knowledge of the Variation of the Compass. But
the present Age, and even this Nation, boasts of a Gentleman[1], who
seems to be entrusted with the magnetical Powers themselves. He makes
artificial Magnets, increases in a few Minutes the Powers of real ones
to a surprizing Degree, changes at Pleasure their Poles, and makes that
newly acquired Polarity, permanent. The World, I hope, will not long be
deprived of the Manner, by which these extraordinary Changes are
produced, which as yet this Gentleman thinks proper to conceal. As
Electricity has some Properties in common with Magnetism, as will be
shewn in the Course of these Observations; some new Lights probably may
be thrown upon both. But to return; admitting even, that no substantial
Advantages could arise from the Inquiries before us, (which, however, we
can by no means grant, upon our considering the Effects we already
perceive of its Operations upon human Bodies) whatever tends to enlarge
the Conceptions of the Mind, and to implant in us still more lofty Ideas
of the Almighty Author of Nature, deserves certainly, independent of
other Considerations, our highest Regard._

_THESE Experiments were all made with Glass Tubes of about two Foot
long; the bore about an Inch in Diameter. But a scrupulous Exactness in
these Proportions is no ways necessary. The thinner and lighter these
Tubes are, the sooner they are excited; though they, 'tis true, don't
retain their Power so long as those, which are more thick and
substantial. But where you intend to communicate the electrical Power,
as fast as you excite it, I should prefer a light Tube; though it ought
never to be less than 1/12 of an Inch thick, because of the Danger of
breaking it by the Friction._

_THE Tube, before it is rubbed, should be always made dry and warm,
which may be done by laying it before the Fire. But I cannot omit
hereupon making one further Remark_; viz. _that Glass Tubes, exactly of
the same Dimensions, made at the same Time, and with the same Materials,
vary considerably with regard to their fitness for electrical Purposes.
Clear and dry Air with some degree of cold is most eligible, though I
have succeeded in the greatest Fogs, but with more Difficulty._




                                   TO
                         _Martin Folkes_, Esq;
                                P. R. S.


  _SIR_,

THE Society having heard from some of their Correspondents in _Germany_,
that what they call a Vegetable Quintessence had been fired by
Electricity, I take this Opportunity to acquaint you, that on _Friday_
Evening last I succeeded, after having been disappointed in many
Attempts, in setting Spirits of Wine on Fire by that Power. The
preceding Part of the Week had been remarkably warm, and the Air very
dry, than which nothing is more necessary towards the Success of
Electrical Trials; to these I may add, that the Wind was then Easterly
and inclining to freeze. I that Evening used a glass Sphere as well as a
Tube; but I always find myself capable of sending forth much more Fire
from the Tube than from the Sphere, probably from not being sufficiently
used to the last.

I HAD before observ'd, that although[2] Non-electric Bodies made
electrical, lose almost all that Electricity by coming either within or
near the Contact of _Non-electrics_ not made electrical; it happens
otherwise with Regard to _Electrics per se_, when excited by rubbing,
patting, _&c_; because from the rubbed Tube I can sometimes procure five
or six Flashes from different Parts, as though the Tube of two Foot
long, instead of being one continued Cylinder, consisted of five or six
separate Segments of Cylinders, each of which gave out its Electricity
at a different Explosion.

THE Knowledge of this Theorem is of the utmost Consequence towards the
Success of electrical Experiments; inasmuch as you must endeavour by all
possible Means to collect the Whole of this Fire at the same Time.
Professor _Hollman_ seems to have endeavour'd at this and succeeded, by
having a tin Tube, in one End of which he put a great many Threads,
whose Extremities touch'd the Sphere when in Motion, and each Thread
collected a Quantity of electrical Fire, the Whole of which center'd in
the tin Tube, and went off at the other Extremity. Another Thing to be
observ'd, is to endeavour to make the Flashes follow each other so fast,
as that a Second may be visible before the First is extinguish'd. When
you transmit the electrical Fire along a Sword or other Instrument,
whose Point is sharp, it often appears as a Number of disseminated
Sparks, like wet Gunpowder or _Wild-fire_; but if the Instrument has no
Point, you generally perceive a pure bright Flame, like what is vulgarly
call'd the _Blue-ball_, which gives the Appearance of Stars to fired
Rockets.

THE following is the Method I made use of and was happy enough to
succeed in. I suspended a Poker in silk Lines; at the Handle of which I
hung several little Bundles of white Thread, the Extremities of which
were about a Foot at right Angles from the Poker. Among these Threads,
which were all attracted by the rubbed Tube, I excited the greatest
electrical Fire I was capable, whilst an Assistant near the End of the
Poker held in his Hand a Spoon, in which were the warm Spirits. Thus the
Thread communicated the Electricity to the Poker, and the Spirit was
fired at the other End. It must be observ'd in this Experiment, that the
Spoon with the Spirit must not touch the Poker; if it does, the
Electricity without any flashing is communicated to the Spoon, and to
the Assistant in whose Hand it is held, and so is lost in the Floor.

By these Means, I fired several Times not only the ætherial Liquor or
Phlogiston of _Frobenius_ and rectified Spirit of Wine, but even common
proof Spirit. These Experiments, as I before observ'd, were made last
_Friday_ Night, the Air being perfectly dry. _Sunday_ proved wet and
_Monday_ somewhat warm, so that the Air was full of Vapour; Wind
South-West and cloudy. Under these Disadvantages, on _Monday_ Night I
attempted again my Experiments; they succeeded, but with infinitely more
Labour than the preceeding, because of the Unfitness of the Evening for
such Trials. _Your Candour_ will not permit you to think my Minuteness
trivial, with Regard to the Circumstances of the Weather, who know, how
many Things must concur to make these Experiments succeed. I shall wait
with Impatience for a proper Opportunity to have these Experiments
repeated in your Presence, and am, with the utmost Respect,

                                              _Sir, your most obedient,_
                                              _humble Servant_,

                                              W. WATSON.

                                              _Aldersgate-Street,
                                              March 27. 1746._




                                 TO THE
                             ROYAL SOCIETY.


  GENTLEMEN,

I lately acquainted you, that I had been able to fire Spirit of Wine,
_Phlogiston_ of _Frobenius_, and common proof Spirit, by the Power of
Electricity. Since which (till Yesterday) we have had but one very dry
fine Day; _viz._ _Monday, April 15_. Wind E. N. E.; when about four
o'Clock in the Afternoon, I got my _Apparatus_ ready, and fired the
Spirit of Wine four Times from the Poker as before, three Times from the
Finger of a Person electrified, standing upon a Cake of Wax, and once
from the Finger of a second Person standing upon Wax, communicating with
the first by means of a walking Cane held between their Arms extended.
The horizontal Distance in this Case between the glass Tube and the
Spirit was at least ten Feet.

YOU all know, that there is the repulsive Power of Electricity, as well
as the attractive; inasmuch as you are able, when a Feather or such-like
light Substance is replete with Electricity, to drive it about a Room,
which Way you please. This repulsive Power continues, until either the
Tube loses its excited Force, or the Feather attracts the Moisture from
the Air, or comes near to some non-electric Substance; if so, the
Feather is attracted by, and its Electricity lost in, whatever
Non-Electric it comes near. In electrified Bodies, you see a perpetual
Endeavour to get rid of their Electricity. This induced me to make the
following Experiment. I placed a Man upon a Cake of Wax, who held in one
of his Hands a Spoon with the warm Spirits, and in the other a Poker
with the Thread. I rubbed the Tube amongst the Thread, and electrified
him as before. I then ordered a Person not electrified to bring his
Finger near the Middle of the Spoon; upon which, the Flash from the
Spoon and Spirit was violent enough to fire the Spirit. This Experiment
I then repeated three Times. In this Method, the Person by whose Finger
the Spirit of Wine is fired, feels the Stroke much more violent, than
when the electrical Fire goes from him to the Spoon. This Method for the
Sake of Distinction, we will call the repulsive Power of Electricity.

THE late Dr. _Desaguliers_ has observed in his excellent Dissertation
concerning Electricity, "That there is a Sort of Capriciousness
attending these Experiments, or something unaccountable in their
Phænomena, not to be reduced to any Rule. For sometimes an Experiment,
which has been made several Times successively, will all at once fail."
Now I imagine that the greatest Part, if not the Whole of this Matter,
depends upon the Moisture or Dryness of the Air, a sudden though slight
Alteration in which, perhaps not sufficient to be obvious to our
Faculties, may be perceived by the very subtle Fire of Electricity. For

_1st_, I CONCEIVE, that the Air itself (as has been observed by Dr.
_Desaguliers_) is an _Electric per se_ and of the vitreous Kind;
therefore it repels the Electricity arising from the glass Tube, and
disposes it to electrify whatever non-electrical Bodies receive the
Effluvia from the Tube.

_2dly_, THAT Water is a _non-Electric_, and of Consequence a Conductor
of Electricity; this is exemplified by a Jett of Water being attracted
by the Tube, _from either Electric_'s _per se_ conducting Electricity,
and _non-Electric_'s more readily when wetted; but what is more to my
present Purpose, is, that if you only blow through a dry glass Tube, the
Moisture from your Breath will cause that Tube to be a Conductor of
Electricity.

THESE being premised; in proportion as the Air is replete with watery
Vapours, the Electricity arising from the Tube, instead of being
conducted as proposed, is, by means of these Vapours, communicated to
the circum-ambient Atmosphere and dissipated as fast as excited.

THIS Theory has been confirmed to me by divers Experiments, but by none
more remarkably than on the Evening of the Day I made those
before-mention'd; when the Vapours, which in the Afternoon by the Sun's
Heat, and a brisk Gale were dissipated, and the Air perfectly dry,
descended again in great Plenty upon the Absence of both, and the
Evening was very damp. For between seven and eight o'Clock, I attempted
again the same Experiments in the same Manner, without being able to
make any of them succeed; though all those mention'd in this Paper with
others of less Note, were made in Half an Hour's Time.

I AM the more particular in this, being willing to save the Labour of
those, who are desirous of making these Kind of Trials; for although
some of the lesser Experiments may succeed almost at any Time, yet I
never could find that the more remarkable ones would succeed but in dry
Weather.

                                                 _I am, Gentlemen,_
                                                 _Your most obedient,_
                                                 _humble Servant,_
                                                 W. WATSON.

                                                 _London, April
                                                 25. 1745._

[Illustration]




                                 TO THE
                             ROYAL SOCIETY.


  GENTLEMEN,

IN some Papers I lately did myself the Honour to lay before you, I
acquainted you of some Experiments in Electricity; particularly I took
notice of having been able to fire Spirit of Wine by what I call'd the
repulsive Power thereof; which I have not heard had been thought of by
any of those _German_ Gentlemen, to whom the World is obliged for many
surprizing Discoveries in this Part of natural Philosophy.

HOW far strictly speaking the Spirit in this Operation may be said to be
fired by the repulsive Power of Electricity, or how far that Power,
which repels light Substances when fully impregnated with Electricity,
fires the Spirit, may probably be the Subject of a future Inquiry; but
as I am unwilling to introduce more Terms into any Demonstration than
what are absolutely necessary for the more ready Conception thereof, and
as inflammable Substances may be fired by Electricity two different
Ways, let the following Definitions at present suffice of each of these
Methods.

BUT first give me Leave to premise, that no inflammable Substances will
take fire, when brought into or near the Contact of _Electrics per se_
excited to Electricity. This Effect must be produced by non-electrical
Substances impregnated with Electricity received from the exciting
_Electrics per se_. But to return,

_1st_, I SUPPOSE that inflammable Substances are fired by the attractive
Power of Electricity, when this Effect arises from their being brought
near excited non-Electrics.

_2dly_, THAT inflammable Substances are fired by the repulsive Power of
Electricity; when it happens, that the inflammable Substances, being
first electrified themselves, are fired by being brought near
non-Electrics not excited.

THIS Matter will be better illustrated by an Example. Suppose that
either a Man standing upon a Cake of Wax, or a Sword suspended in silk
Lines are electrified, and the Spirit, being brought near them, is
fired, this is said to be perform'd by the attractive Power of
Electricity. But if the Man electrified as before holds a Spoon in his
Hand containing the Spirit, or the same Spoon and Spirit are placed upon
the Sword, and a Person not electrified applies his Finger near the
Spoon, and the Spirit is fired from the Flame arising from the Spoon and
Spirit upon such Application; this I call being fired by the repulsive
Power. Of the two mention'd Kinds I generally find the repulsive Power
strongest.

SINCE my last Communication, the Spirit has been fired both by the
attractive and repulsive Power through four Persons standing upon
electrical Cakes; each communicating with the other either by the Means
of a walking Cane, a Sword, or any other non-electric Substance. It has
likewise been fired from the Handle of a Sword held in the Hand of a
third Person.

I HAVE not only fired _Frobenius_'s Phlogiston, rectified-spirit and
common proof-spirit, but also Sal volatile Oleosum, Spirit of Lavender,
dulcified Spirit of Nitre, Peony Water, _Daffy_'s Elixir, _Helvetius_'s
Stiptic, and some other Mixtures where the Spirit has been very
considerably diluted; likewise distilled vegetable Oils, such as that of
Turpentine, Lemon, Orange Peels and Juniper, and even those of them,
which are specifically heavier than Water, as Oil of Sassafras; also
resinous Substances, such as Balsam Capivi and Turpentine; all which
send forth, when warmed, an inflammable Vapour. But expressed vegetable
Oils, as those of Olives, Linseed, and Almonds, as well as Tallow, all
whose Vapours are uninflammable, I have not been able yet to fire; but
these indeed will not fire on the Application of lighted Paper. Besides,
if these last would fire with lighted Paper, unless their Vapours were
inflammable, I can scarce conceive they would fire by Electricity;
because in firing Spirits, _&c._ I always perceive that the Electricity
snaps before it comes in Contact with their Surfaces, and therefore only
fires their inflammable Vapours.

AS an excited non-Electric emits almost all its Fire, if once touch'd by
a non-Electric not excited, I was desirous of being satisfy'd, whether
or no the Fire emitted would not be greater or less in proportion to the
Volume of the electrified Body. In order to this I procur'd an Iron Bar
about five Feet long and near 170 Pounds in Weight; this I electrified
lying on Cakes of Wax and Rosin, but observed the Flashes arising
therefrom not more violent than those from a common Poker. In making
this Experiment, being willing to try the repulsive Force, it once
happen'd that whilst the Bar was at one End electrifying, a Spoon lay
upon the other, and upon an Assistant's pouring some warm Spirit into
the Spoon, the electrical Flash from the Spoon snapped and fired the
first Drop of the Spirit, which unexpectedly fired not only the whole
Jett as it was pouring, but kindled likewise the whole Quantity in the
Pot, in which I usually have it warm'd.

I FIND, in firing inflammable Substances from the Finger of a Man
standing upon Wax, that _cæteris paribus_ the Success is more constant,
if the Man instead of holding the Thread (the Use of which I
communicated in a former Paper) in his Hand, the Thread is suspended at
the End of an Iron Rod held in one Hand, and he touches the Spirit with
one of the Fingers of the other.

IF a Man, standing upon the electrical Cake with a Dish or deep Plate of
Water in one Hand, and the Iron Rod with the Thread in the other, is
made electrical; and a Person not electrified touches any Part either of
the Plate or Water, the Flashes of Fire come out plentifully, and
wherever you bring your Finger very near, the Water rises up in a little
Cone, from the Point of which the Fire is produced, and your Finger,
though not in actual Contact, is made wet. The same Experiment succeeds
through three or more People.

IN firing inflammable Substances, the Person who holds the Spoon in his
Hand to receive the electrical Flashes, when the Finger of the
electrified Person is brought near thereto, not only feels a tingling in
his Hand, but even a slight Pain up to his Elbow. This is most
perceptible in dry Weather, when the Electricity is very powerful.

THERE is a considerable Difficulty in firing _Electrics per se_, such as
Turpentine, and Balsam Capivi, by the repulsive Power of Electricity;
because in this Case these Substances will not permit the Electricity to
pass through them; therefore when you would have this Experiment
succeed, the Finger of the Person, who is to fire them, is to be applied
as near to the Edge as possible of these Substances when warm'd in a
Spoon, that the Flashes from the Spoon (for these Substances will emit
none) may snap, where they are spread the thinnest, and then fire their
Effluvia. This Experiment, as well as several others, serves to confute
that Opinion, which has prevail'd with many, that the Electricity floats
only upon the Surfaces of Bodies.

IF an electrical Cake is dipp'd in Water, it is thereby made a Conductor
of Electricity, the Water hanging about it transmitting the electrical
Effluvia in such a manner, that a Person standing thereon can by no
means be electrified enough to attract the leaf Gold at the smallest
Distance; though the Person standing upon the same Cake when dry,
attracted a Piece of fine Thread hanging at the Distance of two Feet
from his Finger. We must here observe that the Cake being of an unctuous
Substance, the Water will no where lie uniformly thereon, but adhere in
separate Moleculæ; so that in this Instance the Electricity jumps from
one Particle of Water to another, till the Whole is dissipated.

FROM the Appearance of the Threads amongst which I rub the Tube, I can
frequently judge, though the Spirit may be many Feet distant from them,
whether or no it will fire; because when the Persons standing upon the
Wax are made electrical enough to fire the Spirit, the Threads repel
each other at their lower Parts, where they are not confin'd, to a
considerable Distance, and this Distance is in Proportion as the Threads
are made electrical.

IF two Persons stand upon electrical Cakes at about a Yard's Distance
from each other, one of which Persons, for the Sake of Distinction, we
will call A, the other B: If A when electrified touches B, A loses
almost all his Electricity at that Touch only, which is receiv'd by B
and stopp'd by the electrical Cake; if A is immediately electrified
again to the same Degree as before and touches B, the Snapping is less
upon the Touch; and this Snapping, upon electrifying A, grows less and
less, till B being impregnated with Electricity, though receiv'd at
Intervals, the Snapping will no longer be sensible.

THAT Glass will repel and not conduct the Electricity of Glass, has been
mention'd by others, who have treated of this Subject; but the
Experiments to determine this Matter must be conducted with a great deal
of Caution; for unless the glass Tube, intended to conduct the
Electricity, be as warm as the external Air, it will seem to prove the
contrary, unless in very dry Places and Seasons. Thus, I sometimes have
brought a cold, though dry, Glass Tube near three Feet long into a Room,
where there has been a Number of People; when upon placing the Tube upon
Silk Lines, and laying some Leaf Silver upon a Card at one End and
rubbing another Glass Tube at the other, the Silver has, contrary to
Expectation, been thrown off as readily as from an Iron Rod. At first I
was surpriz'd at this Appearance, but then conjectur'd, that it must
arise from the Coldness of the Glass, condensing the floating Vapour of
the Room; in Order then to obviate this, I warm'd the Tube sufficiently,
and this Effect was no longer produced, but the Silver lay perfectly
still.

IF a Number of Pieces of finely spun Glass cut to about an Inch in
Length, little bits of fine Wire of the same Length of what Metal you
please, and small Cork Balls, are either put all together, or each by
themselves, into a dry pewter Plate, or upon a Piece of polish'd Metal,
they make in the following Manner a very odd and surprizing Appearance.
Let a Man, standing upon electrical Cakes, hold this Plate in his Hand
with the bits of Glass, Wire, _&c._ detached from each other, as much as
conveniently may be; when he is electrified, let him cause a Person
standing upon the Ground to bring another Plate, his Hand, or any other
Non-Electric, exactly over the Plate containing these Bodies. When his
Hand, _&c._ is about eight Inches over them, let him bring it down
gently: As it comes near, in proportion to the Strength of the
Electricity, he will observe the bits of Glass first raise themselves
upright; and then, if he brings his Hand nearer, dart directly up and
stick to it without snapping. The bits of Wire will fly up likewise, and
as they come near the Hand, snap aloud; you feel a smart Stroke, and see
the Fire arising from them to the Hand at every Stroke; each of these,
as soon as they have discharged their Fire, falls down again upon the
Plate. The Cork Balls also fly up, and strike your Hand, but fall again
directly. You have a constant Succession of these Appearances as long as
you continue to electrify the Man, in whose Hand the Plate is held; but
if you touch any part either of the Man or Plate, the Pieces of Glass,
which before were upon their Ends, immediately fall down.

SOME few Years ago, Sir _James Lowther_ brought some Bladders fill'd
with inflammable Air, collected from his Coal-mines, to the Royal
Society. This Air flam'd upon a lighted Candle being brought near it.
This Inflammability has occasion'd many terrible Accidents. Mr. _Maud_,
a worthy Member of this Society, made at that Time by Art, and shew'd
the Society, Air exactly of the same Quality. I was desirous of knowing
if this Air would be kindled by electrical Flashes. I accordingly made
such Air by putting an Ounce of Filings of Iron, an Ounce of Oil of
Vitriol and four Ounces of Water into a Florence Flask; upon which an
Ebullition ensued, and the Air, which arose from these Materials, not
only fill'd three Bladders, but also, upon the Application of the Finger
of an Electrified Person, took Flame and burnt near the Top and out of
the Neck of the Flask a considerable Time. When the Flame is almost out,
shake the Flask and the Flame revives. You must with your Finger dipped
in Water, moisten the Mouth of the Flask as fast as it is dried by the
Heat within, or the Electricity will not fire it: Because the Flask
being an Electric _per se_ will not snap at the Application of the
Finger, without the Glass being first made non-electric by wetting. It
has sometimes happen'd, if the Finger has been applied before the
inflammable Air has found a ready Exit from the Mouth of the Flask, that
the Flash has fill'd the Flask, and gone off with an Explosion equal to
the firing of a large Pistol, and sometimes indeed it has burst the
Flask. The same Effect is produced from the Spirit of Sea Salt, as from
Oil of Vitriol; but as the Acid of Sea Salt is much lighter than that of
Vitriol, there is no Necessity to add the Water in this Experiment.

THOSE who are not much acquainted with Chemical Philosophy, may think it
very extraordinary, that from a Mixture of cold Substances, which both
conjunctly and separately are uninflammable, this very inflammable
Vapour should be produced. In order to solve this, it may not be
improper to premise, that Iron is compounded of a Metallic as well as a
sulphurous Part. This Sulphur is so fix'd, that, after heating the Iron
red hot, and even melting it ever so often, the Sulphur will not be
disengaged therefrom: But upon the Mixture of the Vitriolic Acid, and by
the Heat and Ebullition which are almost instantly produced, the
Metallic Part is dissolved, and the Sulphur, which before was intimately
connected therewith, being disengaged, becomes volatile. This Heat and
Ebullition continues 'till the Vitriolic Acid is perfectly saturated
with the Metallic Part of the Iron, and the Vapour once fired continues
to flame, until this Saturation being effected, no more of the Sulphur
flies off.

I HAVE heretofore mentioned, how considerably perfectly dry Air conduces
to the Success of these Experiments; but we have been lately informed by
an Extract of a Letter, that _Abbé Nolet_ was of Opinion, that they
would succeed in wet Weather, provided the Tubes were made of Glass,
tinged blue with Zaffer. I have procured Tubes of this Sort, but, after
giving them many candid Trials, I cannot think them equal to their
Recommendation. I first tried one of them in a smart Shower of Rain
after a dry Day, when the Drops were large, and the Spirit fired three
Times in about four Minutes; the same Effect succeeded, under the same
Circumstances, from the white one; but after three or four Hours
raining, when the Air was perfectly wet, I never could make it succeed.
And to illustrate this Matter further, I have been able when the Weather
has been very dry, with once rubbing my Hand down this blue Tube, and
applying it to the End of an Iron Rod six Feet long, to throw off
several Pieces of Leaf-Silver lying upon a Card at the other End of this
Rod, whereas I never have been able to throw it off by any Means in very
wet Weather. Besides, I am of Opinion, that after the Electrical Fire is
gone from the Tube, the Tube has no Share in the conducting of it; my
Sentiments on that Head I laid before you in a former Paper: For if the
Silk Lines are wetted, they diffuse all the Electricity, and the same
Effects happen when the Air is wet, be your Glass of what Colour it
will. It may not be improper here to observe, that Zaffer, which is used
by the Glass-makers and Enamellers, is made of Cobalt or Mundick
calcin'd after the subliming the Flowers. This being reduced to a very
fine Powder, and mixt with twice or thrice its own Weight of finely
powdered Flints, is moisten'd with Water and put up in Barrels, in which
it soon runs into a hard Mass and is call'd Zaffer.

A DRY Sponge hanging by a Pack-thread at the End of an electrified
Sword, or from the Hand of an electrified Man, gives no Signs of being
made electrical; if it is well soak'd in Water, wherever it is touched,
you both see and feel the electrical Sparks. Not only so, but if it is
so full of Water, that it falls from the Sponge, those Drops in a dark
Room, receiv'd upon your Hand, not only flash and snap, but you perceive
a pricking Pain. If you hold your Hand, or any non-electrical
Substances, very near, the Water which had ceased dropping when the
Sponge was not electrified, drops again upon its being electrified, and
the Drops fall in Proportion to the receiv'd Electricity, as though the
Sponge were gently squeez'd between your Fingers. I was desirous to know
if I was able to electrify a Drop of cold Water, dropping from the
Sponge, enough to fire the Spirit; but after many unsuccessful Trials, I
was forced to desist; because the cold Water dropping from the Sponge
not only cool'd the Spirit too much, but also render'd it too weak;
likewise, every Drop carried with it great Part of the Electricity from
the Sponge. I then consider'd, in what Manner, I could give a Tenacity
to the Water, sufficient to make the Drops hang a considerable Time, and
this I brought about by making a Mucilage of the Seeds of Fleawort. A
wet Sponge then, squeez'd hard and fill'd with this cold Mucilage, was
held in the Hand of an electrified Man, when the Drops forced out by the
Electricity, assisted by the Tenacity of the Liquor, hung some Inches
from the Sponge, and by a Drop of this I fir'd not only the Spirit of
Wine, but likewise the inflammable Air before mentioned, both with and
without the Explosion. What an extraordinary Effect is this! That a Drop
of cold Water (for the Seeds contribute nothing but add Consistence to
the Water) should be the Medium of Fire and Flame.

CAMPHOR is a vegetable Resin, and of Consequence an Electric _per se_.
This Substance, notwithstanding its great Inflammability, will not take
fire from the Finger of a Man or any other Body electrified, though made
very warm and the Vapours arise therefrom in great Abundance. Because,
neither Electric's _per se_ excited, or electrified Bodies, exert their
Force by snapping upon Electric's _per se_, though not excited. If you
break Camphor small and warm it in a Spoon, it is not melted by Heat
like other Resins; but if that Heat were continued it would all prove
volatile. To Camphor thus warm'd, the Finger of an electrified Man, a
Sword or such-like, will in snapping exert its Force upon the Spoon, and
the circum-ambient Vapour of the Camphor will be fired thereby, and
light up the whole Quantity exposed. The same Experiment succeeds by the
repulsive Power of Electricity.

A POKER thoroughly ignited put into Spirit of Wine, or into the
distilled Oil of Vegetables, produces no Flame in either; it indeed
occasions the Vapours to arise from the Oil in great Abundance. But if
you electrify this heated Poker, the electrical Flashes presently kindle
Flame in either. The Experiment is the same with Camphor. These
Experiments, as well as the following, sufficiently evince, that the
electrical Fire is truly Flame, and that extreamly subtil.

I HAVE made several Trials in order to fire Gunpowder alone, which I
tried both warm and cold, whole and powder'd, but never could make it
succeed; and this arises in part from its Vapours not being inflammable,
and in part from its not being capable of being fir'd by Flame, unless
the Sulphur in the Composition is nearly in the State of Accension. This
we see by putting Gunpowder into a Spoon with rectified Spirit, which,
when lighted, will not fire the Powder, 'till by the Heat of the Spoon
from the burning Spirit, the Sulphur is almost melted. Likewise, if you
hold Gunpowder ground very fine in a Spoon over a lighted Candle, or any
other Flame, as soon as the Spoon is hot enough to melt the Sulphur, you
see a blue Flame, and instantly the Powder flashes off. The same Effects
are observ'd in the _Pulvis fulminans_, compos'd of Nitre, Sulphur, and
fixed Alkaline Salt. Besides, when the Gunpowder is very dry and ground
very fine, it (as you please to make the Experiment) is either
attracted, or repell'd; so that in the first Case, the End of your
Finger when electrified, shall be cover'd over with the Powder, though
held at some Distance; and in the other, if you electrify the Powder, it
will fly off at the Approach of any non-electrified Substance, and
sometimes even without it. But I can at Pleasure fire Gunpowder, and
even discharge a Musket, by the Power of Electricity, when the Gunpowder
has been ground with a little Camphor or with a few Drops of some
inflammable chemical Oil. This Oil somewhat moistens the Powder, and
prevents its flying away; the Gunpowder then being warm'd in a Spoon,
the electrical Flashes fire the inflammable Vapour, which fires the
Gunpowder: But the Time between the Vapour firing the Powder is so
short, that frequently they appear as the same and not successive
Operations, wherein the Gunpowder itself seems fired by the Electricity;
and indeed the first Time this Experiment succeeded, the Flash was so
sudden and unexpected, that the Hand of my Assistant, who touch'd the
Spoon with his Finger, was considerably scorch'd. So that there seems a
fourth Ingredient necessary to make Gunpowder readily take Fire by
Flame, and that such a one, as will heighten the Inflammability of the
Sulphur. In common Cases the lighted Match or the little Portion of red
hot Glass, which falls among the Powder, and is the Result of the
Collision from the Flint and Steel, fires the Charcoal and Sulphur, and
these the Nitre. But if to these three Ingredients you add a fourth,
_viz._ a Vegetable chemical Oil, and gently warm this Mixture, the Oil
by the Warmth mixes intimately with the Sulphur, lowers its Consistence,
and makes it readily take fire by Flame. In these Operations,
notwithstanding I always made use of the finest scented Oils of Orange
Peel, Lemons, and such like, yet upon the least warming the Mixture, the
rank Smell of Balsam (_i. e._ the ready Solution) of Sulphur was very
obvious.

Read before the R. S.
  _Oct. 24. 1745_.


                     _A Continuation of the Above._

                                                   Read, _Feb. 6. 1745_.

AS Water is a non-electric, and of Consequence a Conductor of
Electricity, I had Reason to believe that Ice was endowed with the same
Properties. Upon making the Experiment I found my Conjectures not
without Foundation; for upon electrifying a Piece of Ice, wherever the
Ice was touched by a non-electric, it flashed and snapped. A Piece of
Ice also held in the Hand of an electrified Man, as in the
beforementioned Processes, fired warm Spirit, chemical vegetable Oils,
Camphor, and Gunpowder prepared as before. But here great Care must be
taken, that by the Warmth of the Hand, or of the Air in the Room, the
Ice does not melt; if so, every Drop of Water therefrom considerably
diminishes the received Electricity. In Order to obviate this, I caused
my Assistant, while he was electrifying, to be continually wiping the
Ice dry upon a Napkin hung to the Buttons of his Coat, and this being
electrified as well as the Ice, prevented any Loss of the Force of the
Electricity. The Experiment will succeed likewise, if, instead of the
Ice, you electrify the Spirit, _&c._ and bring the Ice not electrified
near them. I must observe, that Ice is not so ready a Conductor of
Electricity as Water; so that I very frequently have been disappointed
in endeavouring with it to fire inflammable Substances, when it has been
readily done by a Sword or the Finger of a Man.

In the first Paper[3] I had the Honour to lay before you upon this
Subject, I took Notice of my having observed two different Appearances
of the Fire from electrified Substances; _viz_. those large bright
Flashes, which may be procured from any Part of electrified Bodies, by
bringing a Non-Electric unexcited near them, and with which we have
fired all the inflammable Substances mentioned in the Course of these
Observations; and those, like the firing of wet Gunpowder, which are
only perceptible at the Points or Edges of excited Non-electrics. These
last also appear different in Colour and Form according to the
Substances from which they proceed: For from polished Bodies, as the
Point of a Sword, a Silver Probe, the Points of Scissors, and the Edges
of the Steel-bar made Magnetical by the ingenious Dr. _Knight_, the
electrical Fire appears like a Pencil of Rays, agreeing in Colour with
the Fire from _Boyle_'s Phosphorus; but from unpolished Bodies, as the
End of a Poker, a rusty Nail or such-like, the Rays are much more red.
The Difference of Colour here, I am of Opinion, is owing rather to the
different Reflection of the electrical Fire from the Surface of the Body
from which it is emitted, than to any Difference in the Fire itself.
These Pencils of Rays issue successively as long as the Bodies, from
which they proceed, are exciting; but they are longer and more
brilliant, if you bring any Non-Electric not excited near them, though
it must not be close enough to make them snap. If you hold your Hand at
about two or three Inches Distance from these Points, you not only feel
successive Blasts of Wind from them, but hear also a crackling Noise.
Where there are several Points, you observe at the same Time several
Pencils of Rays.

                   *       *       *       *       *

IT appears from Experiments, that besides the several Properties, that
Electricity is possess'd of peculiar to itself, it has some in common
with Magnetism and Light.


                             PROPOSITION I.

IN common with Magnetism, Electricity counteracts, and in light
Substances overcomes the Force of Gravity. Like that extraordinary Power
likewise, it exerts its Force _in Vacuo_ as powerfully as in open Air,
and this Force is extended to a considerable Distance through various
Substances of different Textures and Densities.


                               COROLLARY.

GRAVITY is the general Endeavour and Tendency of Bodies towards the
Center of the Earth; this is overcome by the Magnet with Regard to Iron,
and by Electricity with Regard to light Substances both in its
Attraction and Repulsion; but I have never been able to discern that
vortical Motion, by which this Effect was said to be brought about by
the late Dr. _Desaguliers_ and others, having no other Conception of its
Manner of acting than as Rays from a Center, which indeed is confirmed
by several Experiments. One of which, very easy to be tried, is, that if
a single downy Seed of Cotton Grass is dropped from a Man's Hand, and in
its Fall comes within the Attraction of the rubbed Tube; the Down of
this Seed, which before seemed to stick together, separates, and forms
Rays round the Center of the Seed: Or if you fasten many of these Seeds
with Mucilage of Gum Arabic, round a Bit of Stick, the Down of them when
electrified, which otherwise hangs from the Stick, is raised up, and
forms a circular Appearance round the Stick. As these light Bodies are
directed in their Motions, only by the Force impressed upon them, and as
their Appearance is constantly _radiatim_, such Appearance by no Means
squares with our Idea of a Vortex. Some have imagined a Polarity also,
when they have observed one end of an excited Glass Tube repel light
Substances, and the other attract them. But this Deception, arising from
the whole Length of the Tube not being excited, but only such Part of it
as has been rubbed; so that as much of the Tube as is held in the Hand,
remains in an unexcited State, and permits light Substances to lie still
thereon, though forcibly repell'd at the other End. This attractive
Power of Electricity acts not only upon Non-electrics, as Leaf-Gold,
Silver, Thread, and such like, but also upon originally Electrics, as
Silk, dry Feathers, little Pieces of Glass and Resin; it attracts all
Bodies, that are not of the same Standard of Electricity, (if I may be
allowed the Expression) as the excited Body from which it proceeds. I
have found no Body however dense, whose Pores are not pervious to
Electricity by a proper Management, not even Gold itself.


                            PROPOSITION II.

IN common with Light, Electricity pervades Glass, but suffers no
Refraction therefrom; I having from the most exact Observations found
its Direction to be in right Lines, and that through Glasses of
different Forms, included one within the other, and large Spaces left
between each Glass.


                               COROLLARY.

THIS rectilineal Direction is observable only as far as the Electricity
can penetrate through unexcited Originally-electrics, and those
perfectly dry; nor is it at all material, whether these Substances are
transparent, as Glass; semidiaphanous, as Porcelain or thin Cakes of
white Wax; or quite opake, as thick woollen Cloth, as well as woven Silk
of various Colours; it is only necessary that they be
Originally-electrics. But the Case is widely different with Regard to
Non-electrics; wherein the Direction, given to the Electricity by the
excited originally-electric, is alter'd as soon as it touches the
Surface of a Non-electric, and is propagated with a Degree of Swiftness
scarcely to be measured in all possible Directions to impregnate the
whole Non-electric Mass in Contact with it, or nearly so, however
different in itself, and which must of Necessity be terminated by an
originally Electric, before the Electricity exerts the least Attraction,
and then this Power is observed first at that Part of the Non-electric
the most remote from the originally-electric. Thus for Example, by an
excited Tube held over it, Leaf Gold will be attracted through Glass,
Cloth, _&c._ held horizontally in the Hand of a Man standing upon the
Floor, and this Attraction is exerted to a considerable Distance. On the
contrary, the rubbed Tube will not attract Leaf Gold or other light
Bodies, however near, through Silver, Tin, the thinnest Board, Paper, or
any other Non-electric, held in the Manner before-mentioned. But if you
rub the Paper over with Wax melted, and by that Means introduce the
originally-electric therein, you observe the Electricity acts in right
Lines, and attracts powerfully. And here I must beg Leave to remind you,
not only of the former Corollary, but of some of the former Experiments
also; by which it appears, that although, to make a Non-electric exert
any Power, we must excite the whole Mass thereof, yet we can excite what
Part, and what only, of an originally-electric we please. Thus we
observe, that Leaf-gold, and the Seed of Cotton-grass, (which grows upon
Boggs and is a very proper Subject for these Inquiries) are attracted
under a Glass Jar made warm[4], and turned Bottom upwards, upon which
are placed Books and several other Non-electrics; and that the Motions
of the light Bodies underneath correspond with the Motions of the Glass
Tube held over them, the Electricity seeming instantaneously to pass
through the Books and the Glass. But this does not happen, till the
Electricity has fully impregnated the Non-electrics, which lie upon the
Glass, which received Electricity is stopped by the Glass, and then
these Non-electrics dart their Power directly through the upper Part of
the Glass after the Manner of Originally-electrics. But if the thinnest
Non-electric, even the finest Paper, as I before mentioned, is held in
the Hand of a Man at the smallest Distance over the Leaf-Gold, and the
Electricity is not stopped, not the least Power will be exerted, and the
Gold will lie still. I must here remark likewise, that this Law of
Electricity is so constant and regular, that I have not found one
Deviation from it; so that even the Quicksilver, spread thin as it
usually is at the Back of a Plate of a Looking-glass, will prevent the
passing through of the electrical Attraction, unless stopped by an
Originally-electric. This Penetration of the electrical Power through
originally-electrics is much greater than has hitherto been imagined,
and has caused the Want of Success to great Numbers of Experiments. I
have been at no small Pains to determine, how far this Power can
penetrate through a dry Originally-electric; and have found by repeated
Trials, that either in a Cake of Wax alone, or of Wax and Resin mixed,
when the Electricity is very powerful, it has passed, I say, in straight
Lines through these Cakes of the Thickness of 2 Inches and 4/10; but I
never could make it act through one of 2 Inches 8/10, for in this it was
perfectly stopped. So that the Cakes commonly made use of to stop the
Electricity, by being too thin, suffer a considerable Quantity of the
electrical Power to pervade them, and be lost in the Floor. I make no
Doubt, if the electrical Power could be more increased, it would
penetrate much further through these Originally-electric Bodies.


                            PROPOSITION III.

ELECTRICITY, in common with Light likewise, when its Forces are
collected and a proper Direction given thereto upon a proper Object,
produces Fire and Flame.


                               COROLLARY.

THE Fire of Electricity (as I have before observed) is extremely
delicate, and sets on Fire, as far as I have yet experienced, only
inflammable Vapours. Nor is this Flame at all heightned by being
superinduced upon an Iron Rod, red hot with coarser culinary Fire, as in
a preceeding Experiment; nor diminished by being directed upon cold
Water. However I was desirous of knowing, if this Flame would be
effected by a still greater Degree of Cold; and in order to determine
this, I made an artificial Cold; by which the Mercury, in a very nice
Thermometer adjusted to _Fahrenheit_'s Scale, was depressed in about 4
Minutes from 15 Degrees above the freezing Point to 30 Degrees below it,
that is, the Mercury fell 45 Degrees. From this cold Mixture, when
electrified, the Flashes were as powerful and the Stroke as smart as
from the red hot Iron. I could have made the Cold more intense, but the
above was sufficient for my Purpose. This Experiment seems to indicate,
that the Fire of Electricity is affected neither by the Presence or
Absence of other Fire. For as red hot Iron, by Sir _Isaac Newton_'s
Scale of Heat, is fixed at 192 Degrees, and as the Ratio between Sir
_Isaac_'s Degrees and _Fahrenheit_'s is as 34 to 180, it necessarily
follows, that the Difference of Heat between the hot Iron and the cold
Mixture is 1040 Degrees; and nevertheless this vast Difference makes no
Alteration in the Appearance of the electrical Flame. We find likewise,
that as the Fire, arising from the Refraction of the Rays of Light by a
_Lens_, and brought to a _Focus_, is observed first at some small
Distance from their Surfaces, to set on Fire combustible Substances; the
same Effect, as I have before observ'd, is produced in like Manner by
electrical Flame.

I MAY perhaps be thought too minute in some of the before-mentioned
Particulars; but in Inquiries abstruse as these are, where we have so
little _a priori_ to direct us, the greatest Attention must be had to
every Circumstance, if we are truly desirous of investigating the Laws
of this surprizing Power. For, as has been said upon another Occasion by
my ever honoured Friend MARTIN FOLKES, Esq; our most worthy President,
"that Electricity seems to furnish an inexhaustible Fund for Inquiry;
and sure Phænomena so various and so wonderful can arise only from
Causes very general and extensive, and such as must have been designed
by the Almighty Author of Nature for the Production of very great
Effects, and such as are of great Moment to the System of the Universe."

IF these Observations receive the Countenance of this learned Society, I
shall think myself sufficiently recompensed, and am,

                                   _Gentlemen, with the highest Esteem,_
                                   _your most Obedient_
                                   _humble Servant_,
                                   W. WATSON.


                                _FINIS._

-----

Footnote 1:

  Dr. _Gowin Knight_, F. R. S.

Footnote 2:

  I call _Electrics per se_ or originally-_electrics_, those Bodies, in
  which an attractive Power towards light Substances is easily excited
  by Friction; such as Glass, Amber, Sulphur, Sealing-wax, and most dry
  Parts of Animals, as Silk, Hair, and such like. I call _Non-electrics_
  or Conductors of Electricity, those Bodies, in which the above
  Property is not at all or very slightly perceptible; such as Wood,
  Animals living or dead, Metals and vegetable Substances. See _Gray_,
  _Du Fay_, _Desaguliers_, _Wheler_, in the Philosophical Transactions.

Footnote 3:

  Page 6.

Footnote 4:

  I have constantly observed, that the electrical Attraction through
  Glass is much more powerful, when the Glass is made warm, than when
  cold. This Effect may proceed from a two-fold Cause: First, warm Glass
  does not condense the Water from the Air, which makes the Glass, as
  has been before[5] demonstrated, a Conductor of Electricity: secondly;
  As heat enlarges the Dimensions of all known Bodies, and consequently
  causes their constituent Parts to recede from each other, the
  electrical Effluvia, passing in straight Lines, find probably a more
  ready Passage through their Pores.

Footnote 5:

  Page 13.

------------------------------------------------------------------------

                          Transcriber's note:

    All footnotes moved to the end of the text.

    Page 5, 'Contract' changed to 'Contact,' "the Contact of
    Non-electrics..."

    Page 6, 'Power' changed to 'Poker,' "I suspended a Poker in silk
    Lines;"

    Page 7, second 'it' struck, "if it does..."

    Page 9, 'o'Clock' rejoined.

    Page 9, period added to 'E. N. E.'

    Page 22, 'erectified' changed to 'electrified,' "and a Person not
    electrified..."

    Page 49, 'it' changed to 'itself,' "not even Gold itself."