INTRODUCTION.
In examining the progress of almost any branch of human knowledge, curiosity must meet with many repulses. By the time the attention of society is attracted to the accumulation of detached truths, which compose a science, it is often impossible to retrace its history. The real origin of most discoveries is obscured by antiquity, their authors have already sunk into oblivion, and important improvements are ascribed to different inventors.
Electricity is however oppressed by few of these difficulties. With the exception of some small discoveries mentioned by ancient authors, this science derives its origin and all its improvements from the two last centuries. Neither is the historian perplexed in giving every invention to its proper author. Those who cultivatedthis science were commonly men of talents and condition; they pursued it with ability and perseverance; and either themselves published the result of their observations, or deposited them in those literary institutions which they found established in their country. The historian of electricity, therefore, with no extraordinary exertion of industry or talent, may fully collect and accurately arrange the materials of his work.
On the subject of electricity nothing earlier is on record than the observation of Thales, that yellow amber, when rubbed, has the property of attracting light bodies.—So struck was he with this property of amber, that he imagined it was animated.
Thales, the contemporary of Pythagoras, was born at Miletus, a city of Ionia, about six hundred years before Christ. Like all the Grecian sages, he travelled into Egypt; lived in that country a number of years; contracted friendships with the priests, then the depositories of science; and became deeply skilled in all their mysteries and learning. Returning to his own country, stored with the knowledge of the East, he was ranked as the first of the seven wise men of Greece, and became the founder of the Ionic school, as Pythagoras did of the Italic.
It may deserve remark that the same philosopher who is recorded to have observed the first phenomenon in electricity, is also said to have discovered the cause of thunder and lightning. We shall give to the curious, the remarkable passage containing this account, as we find it in Apuleius, a learned and eloquent writer of the second century, while he is rapidly enumerating the discoveries of Thales.
Thales Milesius ex septem illis sapientia memoratis viris facile præcipuus: fuit enim geometricæ penes Grajos primus repertor, et naturæ rerum certissimus explorator, et astrorum peritissimus contemplator, maximas res parvis lineis reperit, temporum ambitus, ventorum flatus, stellarum meatus, tonitruum sonora miracula,siderum obliqua curricula, Solis annula reverticula; idem Lunæ vel nascentis incrementa, vel senescentis dispendia, vel delinquentis obstacula.
“Thales the Milesian was decisively the most eminent of the seven famous sages; for he was the first inventor of geometry among the Greeks, the most judicious inquirer into nature, and the most skilful observer of the stars; he made great discoveries by small geometrical lines, the regulation of times and seasons, the theory of the winds, the course of the stars,the wonderful causes of thunder, the oblique motions of the planets, theannual revolution of the sun, the reason of the increase, decrease, and eclipse of the moon.â€[1]
Though it is no where expressly affirmed that electricity was discovered by Thales to be the cause of thunder, yet when the two facts are placed together, they will furnish an additional argument to those writers who contend that the ancients knew much more than we are willing to allow them of those shining truths, which are the peculiar boast of modern ages. Nor should this early discovery, if we could admit it to be real, excite our surprise. Whatever hindrances might impede the progress of the ancients in other branches of knowledge, from the abstruse nature of the subject, or the want of necessary helps, it may rather excite our wonder, that the effects of electricity should remain so long unobserved. The electric fluid is no local or occasional agent; it is coeval with the world; its presence pervades every substance; it is the principal cause of the grandest scenes in nature, and its operations can hardly fail to show themselves wherever bodies are concerned.
From the time of Thales, there is a chasm in the history of electricity for three hundred years. Indeed, natural science of all kind appears to have languished,during this period. Theophrastus, who flourished 371 years before Christ, the disciple and successor of Aristotle, and he to whom the learned are indebted for the preservation of his master’s works, then adds one more fact to the history of electricity.
In his treatise on stones, after speaking of the attractive power of amber, found on the coast of Liguria, he goes on to ascribe the same properties to the lapis lyncurius, the same substance now called tourmaline. “It possesses (says he) an attractive power like amber: and as they say attracts not only straws and leaves, but copper also, and iron, if in small particles.[2]â€
These two discoveries of Thales and Theophrastus are all, on the subject of electricity, that industry has been able clearly to collect from the barren records of antiquity. Pliny indeed has observed that “amber being rubbed with the fingers, and having thereby become warmed, attracts to itself straws and dried leaves, in the same manner as the magnet does iron.†He also attributes to the Lyncurium the same properties.—Solinus and Priscian, also, make similar statements. But as these are no more than what Thales and Theophrastus had remarked before, they are to be considered only as a repetition of what the preceding writershad made known, not as any addition to the information possessed on this subject. In like manner it might be mentioned that Aristotle, Pliny, Oppian and Claudius, were fully acquainted with the benumbing effects produced by the touch of the Torpedo; but as they do not appear to have suspected that these effects were produced by electricity, they cannot be considered as communicating or possessing any additional knowledge in regard to this powerful agent.[3]
On subjects which regard taste, or which address themselves to the imagination, on poetry, eloquence and the fine arts, it is to the ancients we are to look for information and the models of perfection. But onthe various branches of knowledge which depend on observation, on experiment, on investigation, which comprehend all the parts of mechanical philosophy, the philosophers of antiquity afford little that is either new or just. Hurried away by the vivacity of their genius, which their peculiar complexion invited them to cultivate, and the particular circumstances of the age were calculated to inflame, they investigated facts, not that by accumulated discoveries they might lay the foundation of solid science, but so far only as they served to support or illustrate some favourite hypothesis.
Aristotle, to whose profound and elevated genius we are accustomed to turn for satisfactory information on so many other subjects, affords no remarks on electricity, and little worthy of observation on most of the branches of natural science. One, who on this point has a right to speak, observes.—“That though there are several very sublime questions in his physics, which he clears up in a very masterly way, yet the main, the gross of the work is good for nothing, infelix operis summa.[4]â€
From the time of Theophrastus till the beginning of the 17th century of the christian æra, there is no unequivocal evidence that in the science of electricity any discovery or improvement was made, except the solitaryand unimportant fact that jet, and perhaps agate, is endued with the same power as amber, of attracting and repelling light bodies.—Nor is it ascertained by whom, or at what particular period, this fact was added to the slender stock of electrical knowledge which was then possessed. And thus it appears that for the space of about 1900 years, the part of philosophy, of which we trace the history, was nearly stationary.
Electricity as known to the Moderns.
Having seen, in the preceding section, the very limited knowledge of electricity possessed by the ancients, we now come to give an account of what may properly be called its real origin, and to trace its progress to the present day. In doing this, we shall be careful to note all the original authors who have touched upon this subject; and to exhibit most of their discoveries.
We believe it to be generally the case, that, in the earlier periods of a science, the mind is curious to observe the gradual developement of principles, and the gradual increase of facts, however unimportant these facts may afterwards appear. But as the science progresses,as the ground widens and observations multiply, this curiosity proportionably abates, and we require of the historian selection rather than detail.
However minute, therefore, the history of the first stages of this branch of philosophy must be, the after periods will exact only a careful selection of those more prominent discoveries, which show the advances of the science and mark its gradations.
During the sixteenth century, the phenomena of magnetism having engaged the study of philosophers, they were naturally led to bestow some attention on substances which appeared to possess similar properties with the load-stone. Indeed, it was not till after 1729 that the idea was entertained, that electricity was a distinct fluid, or any thing else than a certain property of bodies, resembling magnetism; nor was any other meaning affixed to the word, than a power of attracting and repelling.
Fifteen centuries having elapsed from the time of Theophrastus, William Gilbert, physician to king James I, in 1600 published a latin work, entitled,De Magnete, magnetesque corporibus, in which, having discussed the phenomena of magnetism, he, towards the close, relates a great variety of electrical experiments.
The principal merit of this philosopher is, that he greatly augmented the list of electrical substances, noted the bodies on which electrics can act, and remarked several circumstances relating to the manner of their action.
He enumerates, as having the power of attracting light bodies, Diamonds, Saphirs, Carbuncles, Iris, Opals, Amethysts, Beryl, Crystal, Bristol-stones, Sulphur, Mastick, Hard Wax, Hard Rosin, Arsenic, Sal-gemm, Rock-Alum, common-glass, Stibium, or glass of Antimony. He also observed that the influence of these substances extended, not only to leaves and straws, but to all matter which was not extremely rare. Friction, he says, is, in general, necessary to excite the virtue of these substances; and the most effectual friction, he affirms, is that which is light and quick. Electrical appearances, he asserts, were strongest when the air was dry, and the wind north or east, at which time electrics would act ten minutes after excitation.
The simple experiments of this philosopher were mostly made with long thin pieces of metal, and other substances freely suspended on their centers, to the extremities of which he presented the electrics he had excited.
The phenomena of magnetism were accounted for, in the time of Gilbert, by means of emanating effluvia, and he applies the same theory to the explanation of electrical attraction, imagining it to be performed in the same manner as the attraction of cohesion. Two drops of water, rush together when they are brought into contact, and electrics, he says, are virtually brought into contact by means of their effluvia.Effluvia illa tenuiora concipiunt et amplectuntur corpora, quibus uniuntur, et electris tanquam extensis brachiis, et ad fontem propinquitate, invalescentibus effluviis, deducuntur.“Those subtle effluvia continually embrace certain bodies, to which they are united, as it were by their extended electric arms; and the effluvia prevailing, the bodies are drawn to the contiguous source of the effluvia.â€
Gilbert has been stiled the father of modern electricity; and when we consider how little was known of the subject prior to his time, and the merit that belongs to himself, not only from his own experiments, but also from turning the attention of philosophers to a new branch of natural science, we cannot but allow that he eminently deserves the title.
Cabeus followed Gilbert, but did little else than add to the list of electrics, wax, gum elemi, Gum guaiaci, Pix Hispanica and Gypsum.
Thirty years after the publication of Gilbert’s work, the celebrated Sir Kenelm Digby, in his “Treatise of the nature of Bodies,†touches upon electricity: but as the age in which he lived was still busying itself with the hypothetical philosophy of Aristotle, so this philosopher in what he says of electricity, appears to be rather amusing himself in inventing theories, to explain the manner in which electric attraction is performed, than in advancing the science by new facts and experiments. His theory of electric attraction is, however, of some celebrity: it was allowed by his contemporary Des Cartes, in his principles of philosophy, and was embraced by the chief writers of his age; though it does not differ essentially from that of Gilbert.
“Attraction (says he) is made by a tenuious emanation, or continued effluvium, which after some distance retracteth into itself, as is observable in drops of syrups, oil and seminal viscosities, which spun at length, retire to their dimensions. Now these effluviums advancing from the body of an electric, in their return do carry back the bodies whereon they have laid hold, within the sphere or circle of their continuities; and these they do not only attract, but with their viscous arms, hold fast a good while after. And if any shall wonder why these effluvium issuing forth, impel and protrude not the straw before they can bring it back; it is because theeffluvium passing out in a smaller thread, and more enlengthened filament, stirreth not the bodies interposed; but returning into its original, falls into a closer substance and carrieth them back into itself.â€
Sir Thomas Brown succeeded to Sir Kenelm Digby. In his “Inquiry into Vulgar Errors,†this inquisitive philosopher has a chapter on electricity, in which he corrects some mistakes into which his predecessor had fallen, adds some new experiments of his own, and gives us a summary view of the state of electrical knowledge at the time he wrote.
“By electrical bodies, (says he) I understand not such as are metallical, mentioned byPliny, and the ancients; for theirelectrumwas a mixture made of gold, with the addition of a fifth part of silver; a substance now as unknown as trueAurichalcum, orCorinthianbrass, and set down among things lost byPancirollus. Nor by electric bodies do I conceive such only as take up shavings, straws, and light bodies, in which number the ancients only placedJetandAmber; but such as conveniently placed unto their objects attract all bodies palpable whatsoever. I say conveniently placed, that is, in regard of the object, that it be not too ponderous, or any way affixed; in regard of the agent, that it be not foul or sullied, but wiped, rubbed, and excitated;in regard of both, that they be conveniently distant, and no impediment interposed. I say, all bodies palpable, thereby excluding fire, which indeed it will not attract, nor yet draw through it; for fire consumes its effluxions by which it should attract.â€
Brown augmented the list of electrics, and found attraction not only in simple bodies, but in such also as were compounded. He observed, that the attractions of bodies were different. Resinous bodies, he says, attract most vigorously, and “good hard wax so powerfully, that it will convert the needle almost as actively as the load-stone. Gums easily dissolved in water, draw not at all; no metal attracts, nor wood, though never so hard and polished. “Glass, (he says,) attracts but weakly, though clear: and some slick stones, and thick glasses but indifferently.â€
These experiments on the electricities of bodies, he performed by means of a needle, “settled freely upon a well pointed pin, so that the electrics might be applied to it without disadvantage;†he tried them also in straws and paleous bodies, powders of wood and iron, in gold and silver foliated.
How the attraction of electrics is performed, he acknowledges is not easily determined; though, he says,“that it is performed by effluviums is plain, and granted by most; for electrics will not commonly attract, except they grow hot and perspirable. For if they be foul and obnubilated, it hinders their effluxion; nor if they be covered, though but with linen or sarsenet, or if a body be interposed, for that intercepts theeffluvium. If also a powerful and broad electric of wax oranimebe held over fine powder, the atoms or small particles will ascend most numerously unto it; and if the electric be held unto the light, it may be observed that many thereof will fly, and be as it were discharged from the electric to the distance sometime of two or three inches. Which motion is performed by the breath of theeffluviumissuing with agility; for as the electric cooleth, the projection of the atoms ceaseth.â€
Sir Francis Bacon in his “Physiological Remains,†has inserted a catalogue of bodies attractive and not attractive; but he differs in nothing worth mentioning from his predecessors.
Mr. Boyle, who so eminently distinguished himself in the latter part of the seventeenth century, was led by the study of chemistry, to give some attention to electricity. He enlarged the catalogue of electrics; and noticed some circumstances relating to electrical attraction, which had escaped former philosophers. The electricalproperties of bodies he found were increased by wiping and warming them, before they were rubbed. Bodies of all kinds, he observed, were indiscriminately attracted; and this attraction he supposed took place in vacuo as well as in the open air.
Hitherto the attraction of electrics was the single phenomenon noticed by philosophers. Gilbert, even when remarking on the characteristic differences between magnetism and electricity, observes, that in magnetism there is both attraction and repulsion, but in electricity only the latter, and not the former.[5]Boyle made an approach to the discovery of this fact of electrical repulsion, by remarking that light bodies, as feathers &c. would cling to his fingers and other substances, after they had been attracted by electrics.
Otto Guericke, the celebrated inventor of the air pump, who was contemporary with Mr. Boyle, improved the science much farther. He made use of a sulphur globe, whirled on an axis, much in the same way with our present glass globes. He could thus excite the electricity with greater power, and try all the experiments of his predecessors to greater advantage. His was the full discovery of electric repulsion. “A body once attracted, he remarks, by an excited electric, is repelledby it, and not attracted again till it has been touched by some other body.†In this manner he kept a feather a long time suspended in the air, above his sulphur globe. He also made another remarkable discovery, which has since been very generally overlooked; namely, that a feather, when repelled by an excited electric, always keeps the same face towards the body which repels it, as the moon does to the earth. The electric light was probably observed by Mr. Boyle in the diamond; but Otto Guericke saw it more clearly in the excitation of his glass globe, and also heard the hissing sound which attends it. As this light, however, was exhibited to Dr. Wall, about the same time, in a much finer manner, we shall rather give his account of it.
“I found, says he, upon swiftly drawing a well polished piece of amber in the dark, through a piece of woollen cloth, and squeezing it pretty hard with my hand, a prodigious number of little cracklings were heard, and every one of them produced a flash of light; but when the amber was drawn gently and slightly through the cloth, it produced only a light, but no crackling; but by holding one’s finger at a little distance from the amber, a large crackling is produced, with a great flash of light succeeding it. And, what to me is very surprising, upon its eruption, it strikes the finger very sensibly, wheresoever applied, with a push or puff, likewind. This light and crackling seems, in some respects, to represent thunder and lightning.
Sir Isaac Newton is the next in chronological order, who made any discovery of importance. He first observed that the electrical attraction and repulsion, penetrated through glass. It cannot but be lamented, that this great philosopher, among the vast variety of important subjects which he cultivated and improved, had not applied himself to electricity, with greater assiduity.
Mr. Hawksbee, in 1709, wrote a treatise on electricity, and distinguished himself by discoveries which far surpassed those of his predecessors. Besides a variety of new facts in regard to attraction and repulsion, he observed the electric light distinctly, and made some delicate and curious experiments on its nature.
The electric light was considered by Mr. Hawksbee, as well as by all those who first observed it, as a species of phosphorus, and all the experiments made, were conducted under this impression.
Holding an exhausted globe within the effluvia of an excited one, he observed a light in the former, which presently died away, if it was kept at rest;but was revived, and continued very strong, if the exhausted globe was kept in motion. The greatest electrical light he produced, was when he enclosed an exhausted cylinder within one not exhausted, and excited the outermost of them, putting them both in motion. He observed no difference, whether the globes were turned in the same direction, or otherwise.
He made many experiments to shew the extreme subtlety of the electric light, and found out a method of rendering opaque bodies transparent. He lined with sealing wax more than half the inside of a glass globe, and having exhausted it, put it in motion. On applying his hand to excite it, he saw the shape and figure of all the parts of his hand distinctly and perfectly, on the concave superficies of the wax within. It was as if there had been pure glass, and no wax interposed between the glass and his hand. This lining was in many places the eighth of an inch thick; and in some places where it did not adhere so closely to the glass as in others, yet the light on these appeared just as on the rest. He repeated these experiments with pitch instead of sealing wax, and with equal success. It is to be regretted that these facts have not engaged more of the attention of philosophers.
After the death of Mr. Hawksbee, twenty years elapsed before any farther improvements were made. The great discoveries which were then making in other branches of philosophy, by Sir Isaac Newton, so absorbed the public attention, that electricity was entirely overlooked. Mr. Grey, after this long interval, took up the subject, and by his discovery of the distinction between electrics and non-electrics, formed an important epoch in the history of electricity.
An account of this discovery of Mr. Grey, is thus abridged from the Philosophical Transactions, by Dr. Priestley. “In the month of February 1729, Mr. Grey, after some fruitless attempts to excite an electric power in metals, recollected a suspicion he had for some time entertained, that as a glass tube, when excited in the dark, communicated its light to various bodies, it might at the same time possibly communicate to them an electricity; that is, a power of attracting light bodies; which, as yet, was all that was understood by the wordelectricity. For this purpose he provided himself with a glass tube, three feet five inches long, and near one inch and two-tenths in diameter. To each end was fitted a cork; to keep the dust out when the tube was not in use. His first experiments were made with a view to determine whether a tube would attract equally well with the ends shut, as with them open.In this respect there was no difference; but he found that the corks attracted and repelled light substances, as well, and rather better than the tube itself. He then fixed an ivory ball upon a stalk of fir about four inches long, and thrusting the end of the stalk into one of the corks, he found the ball endowed with a strong attractive and repulsive virtue. This experiment he repeated in many different ways; fixing the ball upon long sticks, and upon pieces of brass and iron wire, always with the same success; but he constantly observed, that the ball at the end attracted more vigorously, than that part of the wire nearest the tube.
“The inconvenience of using long wires in this manner, put Mr. Grey upon trying whether the ball might be suspended by a pack-thread, with a loop on the tube, with equal success; and the event fully answered his expectation. Having thus suspended bodies of the greatest length he conveniently could, to his tube, he ascended a balcony 26 feet high, and fastening a string to his tube, found that the ball would attract light bodies on the ground below. This experiment succeeded in the greatest heights to which he could ascend; after which, he attempted to carry the electricity horizontally. His first attempt miscarried, because he suspended his line, which was intended to carry the electricity horizontally, by a pack-thread; and thus the fluid got off from it;but though Mr. Grey knew this was the case, he could not at any time think of any method to prevent it.
“On the 30th June 1729, Mr. Grey paid a visit to Mr. Wheeler, in order to give him a specimen of his experiments; but told him of the unsuccessful attempt he had made to carry the electric fluid horizontally; Mr. Wheeler proposed to suspend the conducting line bysilkinstead ofpack-thread. For this advice he could give no reason, but that the silk thread wassmallerthan the other; however, with it they succeeded perfectly well. Their first experiment was in a matted gallery at Mr. Wheeler’s house, on the 2d of July 1729. About four feet from the end of the gallery they fastened a line across the place. The middle of this line was silk, the rest pack-thread. Over the silken part they laid one end of the conducting line, to which was fastened the ivory ball, and which hung down about nine feet below the line stretched across the gallery. The conducting line was about 80 1–2 feet in length, and the other end of it was fastened by a loop to the electric tube. Upon rubbing the tube, the ivory ball attracted and repelled light substances, as the tube itself would have done. They next contrived to return the line, so that the whole length of it amounted to 147 feet; which also answered pretty well. But suspecting that the attraction would be stronger, withoutdoubling or returning the line, they made use of one carried straight forward, for 124 feet; and as they expected, found the attraction in this manner, stronger than when the lines had been doubled. Thus they proceeded with their experiments; still adding more conducting line, till at last their silk string broke with the weight. This they endeavoured to supply, first with a small iron wire, and then with a brass one. The result of these experiments, however, soon convinced them, that the silk refused to conduct the electric fluid, not on account of itssmallness, as they had supposed, but on account of some difference in the matter. The wires were smaller than the silk threads, yet the electricity was effectually carried off by them. They had recourse, therefore, to thicker lines of silk; and thus conveyed the electric matter to the distance of 765 feet: nor did they perceive the virtue to be at all diminished by the distance to which it was carried.†In the manner in which silk was found to be a non-conductor, the same quality was also discovered in many other substances, such as hair, rosin, &c.
Mr. Grey also made many electrical experiments on fluids and animal bodies. As he knew no other method of trying whether bodies were electrified or not, but by making them raise light bodies placed under them, to put a fluid in this situation, he dissolved soap in Thameswater, and suspending a tobacco pipe, he blew a bubble at the head of it; and bringing the excited tube near the small end, he found the bubble to attract leaf brass to the height of two and of four inches.[6]He contrived afterwards, by a curious experiment to shew the effects of electricity upon water, in a more satisfactory manner. He filled a small cup with water higher than the brim, and when he had held an excited tube over it, at the distance of about an inch or two, he says, that if it were a large tube there would first arise a little mountain of water from the top of it, of a conical form; from the vertex of which there proceeded a light, very visible when the experiment was performed in a dark room, and a snapping noise almost like that which was made when the finger was held near the tube, but not quite so loud, and of a more flat sound. Upon this, says he, immediately the mountain, if I may so call it, falls into the rest of the water, and puts it into a tremulous and waving motion. This experiment he repeated in the sun-shine, when he perceived small particles of water thrown from the top of the mountain; and sometimes a fine stream of water would arise from the vertex of the cone, in the manner of a fountain, from which issued a fine stream or vapour, whose particles were so small as not to be seen. This last circumstance he inferred, from the under side of the tube being wet.And by after experiments, he found that though the cylinder of water does not always rise, yet that there is always a stream of particles thrown on the tube, and sometimes to such a degree as to become visible.
In April 1730, Mr. Grey suspended a boy on hair lines, in a horizontal position, just as all electricians had before been used to suspend their hempen lines of communication, and their wooden rods; then bringing the excited tube near his feet, he found that leaf brass was attracted by his head, with a vigour sufficient to raise it to the height of eight, and sometimes of ten inches. When the leaf brass was put under his feet, and the tube brought near his head, the attraction was small; and when the leaf brass was brought under his head, there was no attraction at all. While the boy was thus suspended, Mr. Grey amused himself with making the electricity operate on several parts of his body at the same time, and at the ends of long rods, which he made him hold in his hands, and in diversifying the experiments several other ways.
Mr. Grey continued to study electricity as long as he lived; and besides giving a set of fanciful experiments, by which he supposed he had discovered a perpetual attractive power in electrics, he, a little while before his death, entered on another course by which he hopedhe should be able to astonish the world with a new sort of planetarium. “I have lately made (says he) several new experiments upon the projectile and pendulous motions of small bodies by electricity; by which small bodies may be made to move about large ones, either in circles or ellipses, and those either concentric or excentric to the centre of the large body about which they move, so as to make many revolutions about them. And this motion will constantly be the same way that the planets move round the sun, viz. from the right hand to the left, or from west to east. But these little planets, if I may so call them, move much faster in their apogean, than in the perigean part of their orbits; which is directly contrary to the motion of the planets round the sun.†The manner in which these experiments were made, as delivered by him on his death-bed to Dr. Mortimer, was as follows: “Place a small iron globe (said he) of an inch or an inch and a half in diameter, on the middle of a circular cake of rosin, seven or eight inches in diameter, greatly excited; and then a light body, suspended by a very fine thread, five or six inches long, held in the hand over the centre of the cake, will, of itself, begin to move in a circle round the iron globe, and constantly from west to east. If the globe is placed at any distance from the centre of the circular cake, it will describe an ellipse, which will have the same excentricity as the distance of the globe from thecentre of the cake. If the cake of rosin be of an elliptical form, and the iron globe be placed in the centre of it, the light body will describe an elliptical orbit, of the same excentricity with the form of the cake. If the globe be placed in or near one of the foci of the elliptical cake, the light body will move much swifter in the apogee, than in the perigee of its orbit. If the iron globe is fixed on a pedestal an inch from the table, and a glass hoop, or a portion of a hollow glass cylinder excited, be placed round it, the light body will move as in the circumstance mentioned above, and with the same varieties.†He said, moreover, that the light body would make the same revolutions, only smaller, round the iron globe placed on the bare table, without any electrical substance to support it: but he acknowledged that he had not found the experiment succeed if the thread was supported by any thing but the human hand; though he imagined any other animal substance would have answered the purpose.
These experiments occasioned a great deal of speculation. Dr. Mortimer was the only person who was able to repeat them with success, and he only when nobody but himself was the witness. It was therefore generally supposed that both he and Mr. Grey had been deceived: but from some experiments to be related hereafter, it seems probable that the success of Mr.Grey and Dr. Mortimer was owing to their having performed their experiments with candle-light; and the failure of the others to their having attempted them by day light. Notwithstanding which, it is more than probable that Mr. Grey has been deceived in a number of particulars; for no motion can be performed by an artificial excitation of the electric fluid, but what is attended with much irregularity.
Not long after the discovery of Mr. Grey of the difference between conductors and non-conductors, Mr. Du Fay, a French philosopher, (for the “spirit of electricity†had passed from England to France,) discovered, what was afterwards called positive and negative electricity; or as he denominated them the vitreous and resinous electricities. “Chance (says he) has thrown in my way a principle, which casts a new light on the subject of electricity. The principle is, that there are two distinct kinds of electricity, very different from one another, one of which I call vitreous, and the other resinous electricity. The first is that of glass, rock crystal, precious stones, hair of animals, wool and many other bodies. The second is that of amber, copal, gum lac, silk thread, paper, and a vast number of other substances. The characteristics of these two electricities is, that they repel themselves and attract each other. Thus a body of the vitreous electricity repels the vitreous, andon the contrary attracts all those of the resinous. The resinous also repels the resinous and attracts the vitreous. This discovery of Mr. Du Fay was made in consequence of his casually observing, that a piece of leaf gold, repelled by an excited glass tube, and which he meant to chace about the room with a piece of excited gum copal, instead of being repelled by it, as it was by the glass tube, was eagerly attracted.
This doctrine of two different electricities, produced by exciting different substances, was dropped after Mr. Du Fay; and even this philosopher himself adopted at last the opinion of Dr. Franklin that the two electricities differ only in degree, and that the stronger attracts the weaker. Although many of the experiments of Mr. Grey led directly to it, yet to the French philosopher just mentioned, belongs the merit of first drawing the electrical spark from the human body.—And we cannot forbear remarking, in this place on the regular and progressive advances which the human mind makes in the investigation of science. Electrical attraction was, for a long period, the single phenomenon known to philosophers.—Repulsion was then observed to be also a property of electrics.—In the investigation of these we read of the accidental discovery of the electric light.—To this naturally succeeded, Mr. Grey’s distinction between conductors and non-conductors;and then the difference between vitreous and resinous electricities by Mr. Du Fay. We shall have to remark in the sequel of this history, how each succeeding fact and invention grew out of that which immediately preceded it.
The knowledge of electricity did not stop in France. The Germans began to labour in the same field; and with laudable success. Their success arose chiefly from the improvements they made in the electrical apparatus. The simple experiments of Gilbert, and the early electricians, were made by exciting a piece of amber or sulphur. Mr. Boyle found the electric power increased by smoothing the surface of bodies. Otto Guericke made his experiment with aglobe of sulphur, formed by melting that substance in a hollow globe of glass, and afterwards breaking the glass from off it, little supposing that the glass itself would better have answered his intention. In 1709 Mr. Hawksbee first observed the great electric power of glass. He used aglass globe, which he mounted upon an axis, whirling it round, and at the same time applying his hand to it. He also, to increase the power, inclosed an exhausted cylinder within another, exciting the outermost. After Mr. Hawksbee’s death, the glass globe was laid aside, and his successors confined themselves to the use oftubes. Mr. Boze, professor of philosophy at Wittemburgh,in 1742 returned to the use of theglobe. He also added aprime-conductorof tin or iron, supported, at first, by a man standing on cakes of rosin, but afterwards by silken lines extended horizontally, under the conductor. Mr. Winckler, of Leipsic, to excite the globe, substituted acushion, instead of the hand. The electricalstarand the electricalbellswere also the invention of the German philosophers. Dr. Desagulier, likewise, assisted electricians by some electrical terms. He first gave to bodies conveying electricity the name ofconductors; and those in which electricity may be excited by heating and rubbing he callselectrics per se.
In 1745, the attention of Dr. Watson being attracted by the account of the Germans having fired spirits of wine, he applied himself to electricity with much assiduity, and made many valuable and curious discoveries. But though his improvements were considerable, and such as at another time would have excited interest, they were now lost amid the surprise occasioned by the most remarkable discovery that had yet been made in the whole science. This was the accumulation of the electric matter in glass bottles, and the method of giving the electric shock.
The merit of this discovery belongs to Mr. Cuneus, a native of Leyden, from whence it derives its name ofthe Leyden phial.[7]“M. Muschenbroeck, professor in the university in that city, observing with his friends, that electrified bodies, exposed to the common atmosphere, which is always replete with conducting particles of various kinds, soon lost their electricity, and were capable of retaining but a small quantity of it, imagined, that were the electrified bodies terminated on all sides by original electrics, they might be capable of receiving a stronger power, and retaining it a longer time. Glass being the most convenient electric for this purpose, and water the most convenient non-electric, they first madetheir experiments with water in glass bottles; but no considerable discovery was made, till the professor, or Mr. Cuneus, happening to hold his glass vessel in one hand, containing water, which had a communication with the prime-conductor by means of a wire, and with the other hand disengaging it from the conductor (when he imagined the water had received as much electricity as the machine could give) was surprised by a sudden shock in his arms and breast, which he had not in the least expected from the experiment.â€
Wonder is the effect of ignorance, and ignorance begets credulity; but when wonder and credulity are coupled with terror and surprise, we must look for a strange and mishapen progeny. The exaggerated accounts of those who first experienced the electric shock cannot but raise a smile; especially as we may ascertain their real sensations by like experiments upon ourselves.
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 helost 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 Frenchacademy of sciences. But, adds the same author, it is not given to every electrician to die the death of the justly envied Richman.â€
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 theLeyden bottle was owing, not so much to thequantitiesof non-electric matter contained in the glass, as to thenumber of points of non-electric contactwithin 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 acharged 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 thatthe very comb was perfumed. To see the wonderful effects of thesemedicated 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 thebeatificationof 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 theelectrified 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 woulddart 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.â€
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 ofexperiment.—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.â€
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 thehighest 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 makingthem, 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 whereinconsists 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 ofTheoria 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 principleson 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.