Leyden discovery, says; that he felt himself struck in his arms,
shoulders, and breast, so that he lost his breath; and was two days
before he recovered from the effects of the blow and the terror. He
adds, he would not take a second shock for the kingdom of France. Mr.
Allamand who tried the experiment with a common beer glass, affirmed,
that he lost the use of his breath for some moments; and then felt so
intense a pain along his right arm, that he at first apprehended ill
consequences from it, though it soon after went off without any
inconvenience. But the terror of Mr. Winckler of Leipsic exceeded that
of all the rest. The first time he tried the Leyden experiment, he says,
he found great convulsions by it in his whole body: and that it put his
blood into great agitation; so that he was afraid of an ardent fever,
and was obliged to use refrigerating medicines. He also felt a heaviness
in his head, as if a stone lay upon it. Twice, he says, it gave him a
bleeding at the nose, to which he was not inclined; and that his wife
(whose curiosity, it seems, was greater than her fears) received the
shock only twice, and found herself so weak, that she could hardly walk;
and that a week after, upon recovering courage to receive another shock,
she bled at the nose after taking it only once.
Mr. Boze, with other philosophers were, however, far from participating
in the cowardice of the professor of Leipsic. They gathered resolution
to receive a number of electric shocks, as strong as they could be
given. Mr. Boze, indeed, as Dr. Priestley remarks, “with a heroism
worthy of Empedocles, wished he might die by the electric shock, that
the account of his death might furnish an article for the memoirs of the
French academy of sciences. But, adds the same author, it is not given
to every electrician to die the death of the justly envied Richman.”
This experiment, calculated, not only to engage the investigation of the
philosopher, but to raise the vulgar amazement, brought electricity into
general notice.—From this time every body was eager to see and to feel
this prodigy of nature; and numbers of persons, travelling over Europe,
gained a livelihood by exhibiting its appearances and effects. At the
same time, all the electricians were zealous to search into the nature
of this extraordinary phenomenon. Dr. Watson prosecuted experiments to
ascertain how best to succeed with the Leyden phial. He observed that
the force of the shock was not increased by the size or number of the
globes employed in filling it; nor by increasing the quantity of water
in the vessel; but that the power was greatest when the glass was
thinnest, and the water warmer than the ambient air. He was proceeding
with these discoveries, when Mr. Bevis informed him that he found the
electric explosion as great from covering the sides of a pane of glass,
as it could have been from a half pint phial of water. The Doctor upon
this coated large jars with leaf silver, both inside and outside, within
an inch of the top, and from the greatest explosion he produced from
them, drew the conclusion that the effect of the Leyden bottle was
owing, not so much to the _quantities_ of non-electric matter contained
in the glass, as to the _number of points of non-electric contact_
within the glass, and the density of matter of which these points
consisted.
In France, the Abbè Nollet attempted to measure the distance to which
the electric shock might be carried, and the velocity with which it
passes. At one time he electrified 180 of the guards in the king’s
presence; and at another the whole community of the grand convent of the
Carthusians at Paris, forming a line of 900 toises, by means of iron
wires between every two persons; when the whole company, upon the
discharge of the phial, gave a sudden spring at the same instant of
time, and all felt the shock equally.
But these attempts of the French philosophers to measure the electric
circuit were insignificant, in comparison with the extended and numerous
experiments of Dr. Watson, accompanied by a number of English gentlemen
of eminence. Those gentlemen, in their first attempt, conveyed the
electric shock across the river Thames; making use of the water of the
river as a part of the chain of communication. This was accomplished by
fastening a wire all along the Westminster bridge, at a considerable
height above the water. One end of this wire communicated with the
coating of a charged phial, the other being held by an observer, who, in
his other hand, held an iron rod which he dipped into the river. On the
opposite side of the river stood a gentleman, who likewise dipped an
iron rod into the river with one hand, and in the other held a wire the
extremity of which might be brought into contact with the wire of the
phial.
Upon making the discharge, the shock was felt by the observers on both
sides of the river, but more sensibly by those who were stationed on the
same side with the machine; part of the electric fluid having gone from
the wire down the moist stones of the bridge, thereby making several
shorter circuits to the phial; but still all passing through the
gentlemen who were stationed on the same side with the machine.—This
was, in a manner demonstrated, by some persons feeling a sensible shock
in their arms and feet, who only happened to touch the wire at the time
of one of the discharges, when they were standing upon the wet steps
which led to the river. In one of the discharges made upon this
occasion, spirits of wine were kindled by the fire which had gone
through the river.
They afterwards undertook to determine whether the electric virtue could
be conveyed along dry ground, and to distinguish, if possible, the
respective velocity of electricity and sound.
For this purpose, they fixed upon a hill, and made their first
experiment on the 14th of August 1747; a time, when, as it happened, but
one shower of rain had fallen during five preceding weeks. The wire
communicating with the iron rod which made this discharge, was supported
all the way upon baked sticks; as was also the wire which communicated
with the coating of the phial, and the observers were distant from each
other two miles. The result of the explosion demonstrated to the
gentlemen present, that the circuit performed by the electric matter was
four miles, viz. two miles of wire, and two of dry ground, the space
between the extremities of the wires.—A distance which, without trial,
as they justly observed, was too great to be credited. A gun was
discharged at the instant of the explosion, and the observers had stop
watches in their hands, to note the moment when they felt the shock;
but, as far as they could distinguish, the time in which the electric
matter performed that vast circuit might have been instantaneous.
Travellers through a new region of science, like travellers through an
unexplored country, too often think themselves absolved from the strict
obligations of truth, and at liberty to amuse the public with romantic
accounts of what they have heard and seen. About the time these
experiments were going forward in England, the passion for the
marvellous strongly discovered itself in relating some effects of
electricity, pretended to be found out in Italy and Germany. It was
asserted by Signor Privati of Venice, and after him by Verati at
Bologna, Mr. Blanchi at Turin, and Mr. Winckler at Leipsic, that if
odoriferous substances were confined in glass vessels, and the vessels
excited, the odours and other medical virtues would transpire through
the glass, infest the atmosphere of the conductor, and communicate their
virtue to all persons in contact with it; also, that those substances,
held in the hands of persons electrified, would communicate their
virtues to them, so that the medicines might be made to operate without
being taken into the stomach. They even pretended to have wrought many
cures by the help of electricity applied in this way. It was affirmed
that a man who, having a pain in his side had applied hyssop to it by
the advice of a physician, approached a cylinder in which was concealed
some balsam of Peru, and was electrified by it. The consequence was that
when he went home and fell asleep he sweated, and the power of the
balsam was so dispersed that even his clothes, the bed and chamber, all
smelled of it. When he had refreshed himself by this sleep, he combed
his head, and found that the very comb was perfumed. To see the
wonderful effects of these _medicated tubes_, as they were called, Mr.
Nollet travelled into Italy, where he visited all the gentlemen who had
published an account of these alledged facts. But though he engaged them
to repeat their experiments in his presence and upon himself, and though
he made it his business to get all the information he could concerning
them, he returned fully convinced, that in no instance had odour been
found to transpire through the pores of excited glass, and that no drugs
had ever communicated their virtues to people who had only held them in
their hands while they were electrified. He was convinced, however, that
by continued electrification, without drugs, several persons found
considerable relief in various disorders; particularly, that a paralytic
person had been cured at Geneva, and that one who was deaf of an ear,
another who had a violent pain in his head, and a woman with a disorder
in her eyes, had been cured at Bologna: so that from this time we may
date the introduction of electricity into the medical art.
Another wonderful experiment was the _beatification_ of Mr. Boze; which
other electricians, for a long time, endeavoured to repeat after him,
but to no purpose. His description of this remarkable experiment was,
that if, in electrifying, large globes were employed, and the
electrified person stood upon large cakes of pitch, a lambent flame
would by degrees arise from the pitch, and spread itself around his
feet; that from thence it would be propagated to his knees and body,
till at last it ascended to his head; that then, by continuing the
electrification, the person’s head would be surrounded by a glory, such
as is in some measure represented by painters in ornamenting the heads
of saints. Dr. Watson took the utmost pains to repeat this experiment.
He underwent the operation several times, and was supported during the
time of it by solid electrics three feet high. Being electrified very
strongly, he felt a kind of tingling on the skin of his head, and many
other parts of his body. The sensation resembled what would arise from a
vast number of insects crawling over him at the same time. He constantly
observed the sensation to be the greatest in those parts of his body
which were nearest to any non-electric; but no light appeared upon his
head, though the experiment was several times made in the dark, and with
some continuance. At last the Doctor wrote to Mr. Boze himself, and his
answer showed that the whole had been a trick. Mr. Boze acknowledged
that he had made use of a suit of armour, which was decked with many
pieces of steel, some pointed like nails, others like wedges, and some
pyramidal; and that when the electrization was very vigorous, the edges
of the helmet would dart forth rays, something like those which are
painted on the heads of saints.
The identity of electricity and lightning was the next discovery that
engaged the attention of philosophers; and it is a discovery of the
first practical importance. We have already noticed the conjectures
hazarded by the ancients, on this identity, and we may remember that Dr.
Wall, in his experiments on electric light and the crackling with which
electricity is emitted, notices the similarity between it, and the
phenomenon of thunder and lightning. But when the experiment of the
Leyden phial was known to philosophers, this analogy became much more
obvious. The Abbè Nollet, after suggesting that thunder is in the hands
of nature what electricity is in ours, enumerates many points of
resemblance between these two powers, and then says, that meditating on
these points, he concludes “that one might, by taking electricity for
the model, form to ones self, in relation to thunder and lightning, more
perfect and more probable ideas than what have been offered hitherto.”
But though these philosophers, and many others, were struck with this
similarity between the electric fluid and lightning, they did not think
of any method by which their suspicions might be brought to the test of
experiment.—This was first proposed by Dr. Franklin in 1750. He had
before discovered the effects of pointed bodies in drawing off the
electric matter more powerfully than others. This was suggested to him
by one Mr. Thomas Hopkinson, who electrified an iron ball of three or
four inches diameter, with a needle fastened to it, expecting to draw a
stronger spark from the point of it; but was surprised to find little or
none. Dr. Franklin, improving on this hint, supposed that pointed rods
of iron, fixed in the air when the atmosphere was loaded with lightning,
might draw from it the matter of the thunder-bolt, without noise or
danger, into the body of the earth. His account of this supposition is
given by himself in the following words. “The electric fluid is
attracted by points. We do not know whether this property be in
lightning; but since they agree in all the particulars in which we can
already compare them, it is not improbable that they agree likewise in
this; let the experiment be made.”
This suspicion of Dr. Franklin was verified in 1752. The most active
persons in making the experiments by which it was confirmed, were two
French gentlemen, Messrs. Dalibard and Delor. The former prepared his
apparatus at Marly la Ville, situated five or six leagues from Paris;
the other at his own house, on some of the highest ground in that
capital. Mr. Dalibard’s machine consisted of an iron rod forty feet
long, the lower extremity of which was brought into a centry-box, where
the rain could not come; while on the outside it was fastened to three
wooden posts, by long silken strings, defended from the rain. This
machine happened to be the first that was favoured with a visit of the
etherial fire. Mr. Dalibard himself was not at home; but, in his
absence, he had entrusted the care of his apparatus to one Coissier a
joiner, who had served fourteen years among the dragoons, and on whose
courage and understanding he could depend. This artisan had all the
necessary instructions given him; and was desired to call some of his
neighbours, particularly the curate of the parish, whenever there should
be any appearance of a thunder storm. At length the long expected event
arrived. On Wednesday the 10th of May 1752, between two and three in the
afternoon, Coissier heard a pretty loud clap of thunder. Immediately he
ran to the machine, taking with him a phial furnished with a brass wire;
and presenting the wire to the end of the rod, a small spark issued from
it, with a snap like that which attends a spark from an electrified
conductor. Stronger sparks were afterwards drawn, in the presence of the
curate and a number of other people. The curate’s account of them was,
that they were of a blue colour, an inch and a half in length, and
smelled strongly of sulphur. In making them, he received a stroke on his
arm a little below the elbow; but he could not tell whether it came from
the brass wire inserted into the phial, or from the bar. He did not
attend to it at the time; but the pain continuing, he uncovered his arm
when he went home, in the presence of Coissier. A mark was perceived
round it, such as might have been made by a blow with the wire on his
naked skin.
Although it appears from the foregoing statement, that the directions of
Dr. Franklin began to be put in execution in France, he himself
completed the demonstration of his own problem, before he heard of what
was done elsewhere. An account of these experiments will be found in the
scientific part of this work. Since the time of Franklin, there has been
no capital discovery in electricity:—at least, no discovery of such a
nature as to demand a detailed account in this portion of our work.
Experiments and improvements have been made; and numerous electricians
have evinced a very commendable diligence in the cultivation of this
department of knowledge. But their exertions have been directed to the
reason and philosophy of the phenomena already known, to the
classification of the facts, and to the improvement of the apparatus.
Thus Mr. Canton has given a very curious set of experiments upon the
conducting power of air, to ascertain wherein consists the distinction
between the bodies which are conductors, and those which are not. Signor
Beccaria, also, with the same view, experimented upon water and smoke.
But what more properly belongs to history, is to mention the view, which
Mr. Æpinus, of the Imperial Academy of St. Petersburgh, in the year
1759, took of the science of electricity. This gentleman, struck with
the resemblance of the electrical properties of the tourmaline to the
properties of a magnet, which have always been considered as the subject
of mathematical discussion, fortunately remarked a wonderful similarity
in the whole series of electrical and magnetical attractions and
repulsions, and set himself seriously to the classification of them.
Having done this with great success, and having maturely reflected on
Dr. Franklin’s happy thought of plus and minus electricity, and his
consequent theory of the Leyden phial, he at last hit on a mode of
considering the whole subject of magnetism and electricity, which bids
fair for leading to a full explanation of all the phenomena; at least,
as far as to enable us to class them with precision, and to predict what
will be the result of any proposed treatment. The work containing this
hypothesis, was published at Petersburgh, under the title of _Theoria
Electritatis et Magnetismi_, and is pronounced to be “one of the most
ingenious and brilliant performances of the last century.” A summary
view of this theory, and the principles on which it is formed, will be
seen in the course of the ensuing work.
Great improvements in the electrical apparatus have likewise been made
since the time of Franklin; particularly in devising methods to increase
the power of electricity, and to render sensible the slightest
accumulation or deficiency of the electric fluid. We shall, however,
content ourselves, in the conclusion, with only mentioning the
electrophorus and condenser, invented by Mr. Alexander Volta, Professor
of Experimental Philosophy at Como, &c. This last instrument is
honorable to its inventor, not only on account of the extensively useful
purposes to which it has been and may be applied; but, likewise, because
it was discovered, not casually, like most of the electrical apparatus,
but in consequence of scientific deduction and reasoning.
* * * * *
The origin of Galvanism is so recent, that we think it unnecessary to
give any other history of it, than that which will be found connected
with the article in the body of our work.
CONTENTS
OF
THE EPITOME OF
_ELECTRICITY_.
DIVISION I.
Chap. Page.
I. _Explanation of terms; with some general remarks._ 1
II. _Electric substances; with some of the phenomena attending
their excitation._ 3
III. _Of electrics and conductors._ 6
IV. _Of the electrical machine._ 9
V. _Of communicated electricity._ 15
VI. _Of the electric spark._ 16
VII. _Of the influence of pointed bodies on electricity, and
some phenomena attending their operation._ 17
VIII. _Of electric attraction and repulsion._ 21
IX. _Of the Leyden phial._ 26
X. _Of the electrical battery, and experiments performed with
it._ 28
XI. _Of the electrophorus, and some of its phenomena accounted
for._ 33
XII. _Of electrometers._ 36
XIII. _The identity of electricity with lightning._ 40
XIV. _Of the structure and use of the electrical kite._ 41
XV. _The structure and use of lightning rods._ 48
XVI. _Of animal electricity._ 55
XVII. _The influence of electricity on vegetables._ 61
XVIII. _Medical electricity._ 63
XIX. _Directions concerning the use of the electrical
apparatus, with some practical rules for performing
experiments with it, to the best advantage._ 68
DIVISION II.
I. _Entertaining experiments made by electrical attraction
and repulsion._ 73
II. _Experiments with electric light._ 79
III. _Experiments with charged electrics._ 86
IV. _Experiments relating to the influence of pointed bodies
on electricity._ 92
V. _Promiscuous experiments._ 94
DIVISION III.
I. _Introductory observations to the theory of electricity._ 105
II. _Theories of electricity, exclusively of that of
Franklin._ 108
III. _The Franklinian theory of electricity._ 116
APPENDIX.
No.
I. _A description of the cement used for electrical
purposes._ 125
II. _A composition for coating cylinders or globes._ 125
III. _To make the best kind of amalgam for exciting electrics._ 126
IV. _The preparation of electrical paint._ 126
V. _To make the artificial bolognian stone._ 127
CONTENTS
OF
THE EPITOME OF
_GALVANISM_.
Chap. Page.
I. _A short account of the discovery of Galvanism._ 129
II. _Of the animals best fitted for Galvanic experiments; of
the metals best calculated for making these experiments;
and of conductors._ 131
III. _A description of the Galvanic trough and pile._ 134
IV. _The method of performing Galvanic experiments with frogs;
with some conclusions drawn from them._ 138
V. _Various experiments with the Galvanic pile._ 140
VI. _Experiments on the deflagration of metals by the Galvanic
pile._ 143
VII. _Further Galvanic experiments on metals, and on other
substances._ 145
VIII. _Experiments which may be performed without the assistance
of the battery._ 148
IX. _Some common effects which are supposed to be occasioned
by Galvanism._ 150
X. _The effects of Galvanism on vegetables._ 152
XI. _Of medical Galvanism._ 154
XII. _The identity of Galvanism with electricity considered._ 157
EPITOME
OF
ELECTRICITY.
DIVISION I.
CHAP. I.
_Explanation of Terms; with some general Remarks._
If a glass tube be rubbed in the dark with a dry hand or piece of
buckskin, upon applying the knuckle to it a luminous stream or spark
will appear, passing from the glass to the knuckle, attended with a
crackling noise: this luminous spark or stream is called electricity.[8]
It is produced by the friction of several other substances, and was
first observed on amber.—Hence its name, from ηλεκτρον the greek term
for amber. It is a fluid extremely subtle, abounding in all nature, and
is one of her principal agents; which, though generally imperceptible,
sometimes becomes the object of our sight and other senses.
A glass tube, having been rubbed and producing the appearances above
described, is said to be _excited_. The hand or buckskin, by which this
is effected, is called the _rubber_. _Electrics_ are all substances
which can be made to produce the same appearances; the most perfect are
glass, amber, sealing-wax, sulphur, gum lac, rosin &c. These are also
called _non-conductors_, from their inability to conduct the electric
fluid. _Conductors_ or _non-electrics_ are those bodies which cannot be
excited, but have the power of transmitting electricity; such are
metals, water, the bodies of animals, an imperfect vacuum, heat &c. But
strictly speaking, there are no _perfect_ conductors or non-conductors.
A body is said to be in its _natural state_, when it is in the same
state, with respect to electricity, as the mass of the earth.
When a body has more of the electric fluid than its natural quantity, it
is said to be _electrified positively_, when less, _negatively_; but
neither of these cases can occur in a conductor, unless the
communication between it and the earth be cut off by the _intervention
of an electric or non-conductor_. When this happens, the conductor is
said to be _insulated_.