Part 3
Mr. Muschenbroeck, in a letter to Mr. Reaumur, written soon after the 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.
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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.