endeavoured to recover life by violent friction, but in vain. There appeared a red spot on the forehead, from which spirted some drops of blood through the pores, without wounding the skin. The shoe belonging to the left foot was burst open, and uncovering the foot at that part, they found a blue mark; whence it was concluded, that the electric matter having entered at the head, made its way out again at that foot. Upon the body, particularly on the left side, were several red and blue spots resembling leather shrunk by being burnt. Many more also became visible over the whole body, and particularly over the back. That upon the forehead changed to a brownish red, but the hair of the head was not singed. In the place where the shoe was burst, the stocking was entire; as was the coat every where, the waistcoat only being singed on the fore flap: but there appeared on the back of Mr. Solokow's coat long narrow streaks, which probably arose from fragments of the red hot wires falling on it and burning off the nap. Next day, when the body was opened, the cranium was very entire, having neither fissure nor coutra-fissure: the brain was sound; but the transparent pellicles of the windpipe were excessively tender, and easily rent. There was some extravasated blood in it, as also in the cavities below the lungs. Those of the breast were quite sound; but those towards the back of a brownish black color, and filled with more of the blood above-mentioned. The throat, the glands, and the small intestines, were all inflamed. The singed leather-colored spots pene trated the skin only In forty-eight hours the body was so much corrupted that they could with difficulty place it in the coffin. It is said that, at the time of his death, professor Richman had in his pocket seventy rubles of silver, which were not in the least affected by the lightning.

25. There was no longer any doubt remaining as to the identity of lightning, and the electricity produced by the electrical machine; and the great practical use made of this discocovery was to secure buildings, ships, &c., from being damaged by lightning, by erecting on them pointed metallic rods, rising a little above the highest part of the building, and passing along it so as to communicate with the ground or the nearest water, a full account of which will be given in the course of this essay.

26. A short time previous to the event of professor Richman's death, a most remarkable attempt was made by a gentleman in Italy, to gain on the credulity of his countrymen and others, by pretending that if odoriferous substances were enclosed in glass tubes, and the tubes excited, the medicinal virtues of those substances would transpire through the glass, impregnate the atmosphere of the conductor, and thus be readily communicated to the patient without being taken into the stomach. The most astonishing cures were said to have been performed by these medicated tubes; and the inventor, J. Francisco Pivati, published an account of them to the world. Both the British and French philosophers united in investigating the merits of Pivati's experiments, and the result was a complete failure, in every inVEL VIII.

stance in which the experiments were repeated, though this was done in the presence of those who pretended to have been so successful; and, in some cases, with the very apparatus they themselves had used. The theory was, consequently, no longer credited.

27. To enumerate, in chronological order, all the discoveries that have been made in the science of electricity, from the invention of the Leyden phial to the present period, would swell this introductory sketch far beyond its proper limits; and yet, as having so eminently contributed towards raising the science to its present elegant, improved, and highly prosperous state, there are several whose names it would be injustice to pass by in silence. As the chief of these we may notice the following: Mr. Canton, an eminent English electrician, who distinguished himself by a very successful repetition of Dr. Franklin's experiments on atmospherical electricity; a method of electrifying the air of a room, either positively or negatively; and particularly by disproving the correctness of the theory of vitreous and resinous electricity, and showing that every electric is capable of giving it both in a positive and negative form, according to the nature of the surface of the body, and the kind of rubber with which it is excited.

This ingenious electrician made several remarkably fine experiments on electrical atmospheres, which led to the establishment of the fact, that bodies immersed in them became possessed of the electricity the opposite of that of the body into the atmosphere of which they are placed.

28. In connexion with the name of Canton must be mentioned that of Beccaria, author of a work entitled Dell' Elettricismo Artificiale e Naturale, and which was translated into English in the year 1776. The discoveries of Signor Beccaria were nearly the same as those of his contemporary, Mr. Canton, although they had had no communication with each other on the subject. Beccaria also made some very important experiments on the conducting power of water; in these he ascertained, that water is a very imperfect conductor of electricity; that it conducts it according to its quantity, and that, when used in very small quantities, its resistance was greatest. See BECCARIA.

29. Some interesting discoveries were made in the year 1759, on the electrical qualities of silk, by Mr. Symner. An account of these he published in the Philosophical Transactions. His attention seems to have been directed to the subject by accidentally observing, that, on pul ling off his silk stockings in the evening, a crackling noise proceeded from them, and that in the dark they emitted sparks of fire. He found that these electrical appearances were always the strongest when a silk and worsted stocking were both on one leg, and that it was of no consequence which of them was next the skin, but that they must be of different colors, one white and the other black. Two stockings of this description, worn on the leg for the short space of ten minutes, on being pulled off, stood inflated as if the leg had been within them, and, on being drawn asunder, attracted each other at

C

the distance of eighteen mches. These effects are always most powerful when the stockings are new, or when newly washed. Those who choose to try this very simple experiment will find it succeed equally well if the stockings are placed one within the other, drawn a few times through the hand, and then quickly pulled asunder.

30. Mr. Kinnersly, an intimate friend of Dr. Franklin, made several experiments that contributed to the advancement of electricity. These related chiefly to the discovery of the two electricities, the conducting power of water at different temperatures, and the power of strong charges of electricity when passed through brass wires. In the first of these experiments he had been anticipated by M. Du Fay; but he soon perceived that Du Fay did not consider the two electricities in the same light as that in which they were viewed by Franklin, viz. positive and negative.

31. In 1757 a work appeared on electricity, entitled Disputatio Physica Experimentalis de Electricitatibus, by Mr. Wilke, of Rostock, in Lower Saxony, in which the author gives some very interesting details of his researches respecting the electricity developed during the melting and cooling of electrical substances, and also that produced by the friction of different bodies. This gentleman found that, when sulphur is melted in an earthen vessel placed upon conductors of electricity, it is strongly electrified when taken out after it is cold; but that it shows no signs of electricity if cooled upon electrics. Melted sealing-wax, he found, acquired negative electricity when poured into glass vessels, but positive electricity when poured into sulphur. Mr. Wilke also confirmed the experiments of Dr. Franklin and Mr. Canton on electrical atmospheres, and illustrated the phenomena of electrical light.

32. M. Alpinus, a member of the Imperial Academy at St. Petersburgh, seems to have been the first who gave to the world a mathematical demonstration of the theory of electricity. An exposition of his treatise was published by the abbé Hauy; and an excellent paper, on the same subject, was drawn up for the Royal Society by Mr. Cavendish, before he knew any thing of the theory of M. Alpinus. The merits of M. Alpinus are certainly great, but we consider Cavendish as having much higher claims as an electrician; his experiments on the conducting power of water and wire; his very ingenious construction of the artificial torpedo; and above all, his success in employing electricity as a chemical agent, justify this opinion. 33. The labors of Dr. Priestley, as an electrician, are deservedly held in the highest esteem; the doctor brought no common share of ingenuity and perseverance to bear upon the science; and to him we are indebted for a considerable number of important improvements and interesting experiments in electricity, as connected with chemistry; for a most excellent treatise on the History of Electricity; an Introdiction to Electricity: several valuable papers on the same subject, inserted in the Philosophical Transactions; and for numerous improvements in the construction of electrical apparatus.

34. The theories of Alpinus and Cavendish were much improved on by the ingenuity of M. Coulomb. By those philosophers the action of the electric matter, in producing attraction or repulsion, was considered merely as diminishing with the distance; but by the experiments of Coulomb it was proved that the electrical force, like that of gravity, is in the inverse ratio of the squares of the distance. The instrument with which Coulomb made his experiments was of his own construction: he gave it the name of the torsion balance,' from the manner of its action; a description of it will be given in the course of this essay. Coulomb also made numerous experiments for the purpose of ascertaining the laws by which the dissipation of the electrical matter in the air is regulated; and also to ascertain the distribution of it in an overcharged body. In prosecuting these enquiries he was certainly as successful as could possibly be expected, considering the extreme delicacy of his apparatus, and the effects which the variableness of the atmosphere produces on the strongest electrical experiments.

35. To M. De Saussure we are also indebted for some remarkably fine experiments, which seem to have been made with great care, on the electricity developed during the conversion of fluids into vapor. The fluids on which he operated were distilled water, spirit of wine, and ether. The same philosopher likewise made some highly interesting experiments on atmospherical electricity, for the verification of which he made a journey to the Alps.

36. Most of those who have devoted their attention to the study of electricity, as a science, have distinguished themselves by the invention of some new instrument, the use of which has generally led to some important discovery.

This was peculiarly the case with Sig. Volta, professor of natural philosophy at Como in Italy. He invented the electrophorus, an ingeniously constructed instrument for collecting and retaining the electric matter; and another called a condenser, the use of which is to accumulate, and render visible, the smallest portions of electricity, natural or artificial. The celebrity ot Volta, however, rests chiefly on the important improvements which he made in that branch of electricity designated GALVANISM, under which they will be fully considered.

37. We have already noticed the scientific experiments of Coulomb, and must here observe that Dr. Robison, late professor of natural philosophy in the university of Edinburgh, is justly entitled to a share of the honor bestowed on Coulomb, since he had, so early as the year 1769, made numerous and remarkably successful attempts, with an admirable electrometer of his own invention, to determine the laws of electric action. But the professor did not publish an account of his experiments at the time they were made, which certainly gives them the appearance of posteriority. The conclusion to which Dr. Robison's experiments led him was, that the force of electrical attraction and repulsion is nearly in the inverse ratio of the square of the distance.

The specific result,' says Dr. Brewster, which he obtained was, that the mutual repulsion of

ried as d.06 their centres

38. As electricity now began to be more generally cultivated, it was to be expected that great improvements in the construction of apparatus would take place. This was the case; and the brilliant success of Van Marum of Haarlem, in experiments which had failed in the hands of others, was obviously owing to the prodigious power of the large apparatus constructed by Mr. Cuthbertson of London, and placed in Tyler's

museum at Haarlem. Some notice of these ex

periments will be taken in the course of this article; at present it may be sufficient to state, that, whatever other philosophical instrument makers may have conceived, Mr. Cuthbertson has brought forth the most useful, because the most powerful, electrical apparatus with which we are yet acquainted.

39. Mr. Cavallo is justly entitled to respectful notice in every historical sketch of the rise and progress of the electrical science, to which he made many important additions. This philosopher made numerous experiments on atmospherical electricity; and also added to our stock of electrical apparatus, by his invention of the most ingeniously constructed instruments for measuring, doubling, condensing, and multiplying electricity.

40. There are other philosophers who have liberally contributed to the progressive improvement of this branch of natural philosophy, on whose merits we cannot here dwell; but this we the less regret as their improvements and discoveries must be still fresh in the memory of those who feel an interest in the science. Among these we would simply enumerate the ingenious and laborious Nicholson, the venerable M. Hauy, Mr. Brooks, Mr. Bennet, Mr. Henley, Mr. Morgan, La Place, and the truly ingenious

annalist M. Poisson.

40. Many other names of deserved celebrity might be here mentioned, as having successfully labored in raising electricity to its present eminent station among the sciences; but we must bring this part of our article to a conclusion by acknowledging our obligations to them, and intimating that we shall occasionally avail ourselves of their labors. This remark is meant to apply particularly to the excellent treatise on electricity by the late Mr. George John Singer, a popular lecturer on this science. Mr. Singer's name stands high in the scientific world; and competent judges have pronounced his Elements of Electricity and Electro-Chemistry one of the best and most original works on the subject in the English language

PART I.

ON THE PHENOMENA OF EXCITED ELECTRICITY.

41. The more simple methods of exciting electrics enable us to perform several pleasing and instructive experiments, without the aid of costly and complex apparatus; the principal of these we now proceed to describe.

If two silk ribands, the one black and the other white, about two or three feet in length, and perfectly dry, be applied to each other by their surfaces, and then drawn smartly a few times bevelvet or woollen cloth, they will be found to tween the finger and thumb, or over dry silk adhere to each other with considerable force; and when separated at one end will rush together Each riband, when sepaagain with rapidity.

rated, will attract any light substances to which it is presented; and, if the experiment be made in a dark room, a flash of light will occasionally attend the separation of the ribands.

42. Sticks of sealing-wax, resin, or sulphur, when rubbed with dry woollen cloth, or fur; and tubes or rods of glass, when rubbed with silk, exhibit similar powers; and, if of sufficient size, produce, when applied within a short distance of the face or hand, a distinct and singular sensation. These effects having been first produced by the friction of amber (electron) are called electrical phenomena; and the processes employed for their production, the excitation of electricity.

43. Attraction is the phenomenon most constantly attendant on excitation; it is therefore considered as an indication of the presence and action of electricity, and is the basis of all its tests. Electricians formerly, says Mr. Singer, employed for such trials a light wooden or metal needle, supported by its centre on a point, or a the excited body was presented, and, if they were thread or feather delicately suspended. To these attracted by it, the attraction was attributed to electricity, and the excited body was called an electric.

44. This suspended needle, and every other contrivance for the same purpose, they called an electroscope, when employed to indicate the existence of electricity; and an electrometer when considered as a measure of its force; but the latter term appears fully sufficient, since every contrivance hitherto employed to ascertain the presence of electrical phenomena is also calcuelectrometers, for common purposes, are conlated to measure their power. The most useful structed by suspending two narrow slips of gold leaf from the cap of a glass cylinder. When these are unelectrified they will hang parallel and contiguous; the presence of the smallest quantity of electricity will cause them to diverge towards the sides of the cylinder.

Small balls turned from the pith of elder, and suspended by fine threads or silver wires, are sometimes substituted for the gold strips. They are less easily affected, but they are more durable. The pith balls, suspended by thread or wire, are also occasionally used without a glass cylinder. But these and other electrometers will be explained hereafter.

45. Electrical phenomena are thus characterised by the attraction and recession of light substances; the consequent production of motion in them, and of sensation in living bodies, and by the evolution or production of light. There are various methods by which these effects may be produced, but the following are the most ob vious sources of their production. (1.) Friction. (2.) Change of form. (3.) Change of temperature. (4.) Contact of dissimilar bodies.

46. Of the first kind, viz. friction, the instances are most numerous, and, as Mr. Singer remarks, under certain limitations, universal; they may indeed be obtained by rubbing any of an extensive list of resinous and silicious substances; and of dry, vegetable, animal, and mineral productions. The electricity thus excited, is most readily rendered visible by its effects on the gold leaf electrometer.

47. Examples of the second kind are also very numerous. If a small quantity of sulphur be melted and poured into a conical wine glass, it will contract a little, and become electrical in cooling. A silk thread with a small hook at the end of it, or a rod of glass should be inserted in the sulphur while in a fluid state, to serve as a handle for separating it from the glass when cold. On being separated from the glass, the sulphur will exhibit other signs of electricity; if kept in the glass it will retain its electric virtue for years, and evince it very perceptibly on every attempt to separate the two substances.

48. Mr. Henly discovered that chocolate, fresh from the mill, becomes strongly electrical, as it cools in the tin pans. It soon loses this property, but recovers it once or twice, by being melted in an iron ladle and poured into the tin pans. When the mass becomes dry, the electricity cannot be restored by melting, unless olive oil be mixed with it in the ladle; in which case it completely recovers its electric power. M. Chaptal observed the same circumstance during the congelation of glacial phosphoric acid. Calomel also, when it fixes by sublimation to the upper part of a glass vessel, has been found strongly electrical. The condensation of vapor, and the evaporation of fluids, though apparently opposite processes, are alike sources of electrical excitation.

49. Various crystallised gems, and a stone alled the Tourmalin, become electrical by the mere application of heat; but no other substances have yet unequivocally manifested the same property; though the effects of friction are generally increased, if it is preceded by a moderate elevation of temperature.

50. The contact of dissimilar bodies is protably in all cases the real primary cause of electrical excitement, but it is rarely employed alone, for electricity is known to us only by its effects, which are constantly the result of an artificial arrangement, and consequently may not immediately succeed the primary cause of electric powers, similar in their separate action on the electrometer, and other indifferent matter; but everting a mutual influence on each other, destructive of their individual properties.

51. It was at first supposed that these phenomena were peculiar to the substances by which they were produced; hence the power excited by the friction of glass was termed vitreous electricity; and that by the friction of sealing-wax, resinous electricity. It has, however, long since been proved that both powers are produced in every case of electrical excitation; and, because their mutual counteraction of effect resembles that of an affirmative and negative power, they have been styled positive and negative electricity. 52. The determination of these two states of electricity in different excited bodies, continues

Mr. Singer, is of importance to the practica electrician, and may be thus effected :-Sealingwax when rubbed on woollen cloth is negatively electrified. Glass, when rubbed with silk is positively electrified. Let an electrometer he made to diverge by its being approached by an excited stick of sealing-wax: while in this state, approach it with any excited body, the electricity of which is to be determined. If the divergence of the electrometer increase, the presented body is negative; if it be diminished, the pre sented body is positive. In other words, all those substances that lessen the divergence occasioned by excited wax, are positive; and such as increase it, negative: whilst those which lessen the divergence produced by excited glass, are negative; and such as increase it positive. Examining, by this test, the effects produced in some of the instances of excitation already considered, we find the truth of the preceding statements, and the relation of the different electrical states to the processes by which they are produced, become more intelligible. Care ought to be taken to destroy the divergence of the electrometer after every experiment of this nature; this is best effected by touching its cap with one end of a piece of brass wire.

53. As an illustration of the doctrine here advanced let the following simple and easily performed experiments be made.

(1.) Roll up a warm and dry piece of flannel, so that it may be held by one extremity, while a stick of sealing-wax is rubbed with the other. After a slight friction present the flannel to an electrometer, which will instantly diverge; while this divergence continues, bring the stick of sealing-wax near the cap, and the leaves of the electrometer will quickly collapse. Both these substances, it is obvious, are electrified by mutual friction, but their electricities are opposite, that of the wax being negative, and that of the flannel positive.

(2.) The electricities thus produced are equal to each other: for if the friction be repeated, and the two substances be both presented to the electrometer at the same time, no signs of electricity appear: the opposite electricities, when applied together, producing a reciprocal counteraction of effect.

(3.) If a black and a white silk riband be excited in contact, in the manner already described, the black riband will be found to be negatively, and the white one positively electrified.

(4.) Take the sulphur cone described at 47, apply it and the glass separately to the electrometer; the cone will be found to be negatively and the glass positively electrified.

54. From the above experiments it appears, that in all cases of excitation positive and negative electricity are produced at the same time, and may be observed by the use of proper means. But it also appears that by friction with the same substance, different bodies are variously affected; for glass rubbed with silk evinces positive electricity: but wax rubbed with silk is rendered negative. Again, polished glass, when rubbed with silk, skin-wool, or metal, becomes positive; but if it be excited by friction against the back of a living cat, it appears negative. Wool, silk,

or fur, rubbed against sealing-wax, are rendered positive; but gold, silver, or tin, are by the same process rendered negative.

55. Electricians have drawn up tables for

Black silk

Sealing wax.

Positive Negative Positive Negative

Baked wood

In a note appended to the preceding table Mr. Singer says, Mr. Cavallo had inserted metals, which appeared to imply that the friction of all metals electrified sealing-wax positively; this I find is not the case: iron, steel, plumbago, lead, and bismuth, render sealing-wax negative, and all the other metals I have tried leave it positive. I have therefore made a slight alteration in the table. The least difference in the conditions of such experiments will occasion singular varieties of result: with the same rubber (an iron chain), positive electricity may be excited in one stick of sealing-wax, and negative in another, if the former have its surface scratched, and the latter be perfectly smooth. Many repetitions of each experiment are therefore essential to an accurate conclusion.

56. The result of experiments of the kind just described, Mr. Singer found to be much influenced by the state of the bodies employed, and the manner in which the friction was applied to them. In general, he remarks, strong electric signs can only be produced by the friction of dissimilar bodies; but similar substances, when rubbed together so that the motion they individually experience is unequal, are sometimes electrified; and, in such cases, the substance of which the friction is lim ted to the least extent of surface, is usually ne ative. This he farther remarks is the case with the strings of a violin, over a limited part of which he bow passes in its whole length, and the hairs of the bow become positive.

57. From these facts he draws the following conclusions, viz. that positive and negative electricity are concomitant phenomena, and that in all cases of electrical excitement, they are both produced, though one only may occasionally appear; and that these phenomena are not peculiar to any distinct class of bodies, but may be produced alternately in various substances, by changing the materials or method by which friction is communicated to them.

THE COMMUNICATION OF ELECTRICITY. 58. Mr. Cavallo, speaking of communicated electricity, remarks, that under such a title falls almost all that we know of the subject: the passage of this virtue, says he, from one body to another is what causes its light; by being communicated to other bodies we see its attraction; by its quick transition it melts metals, destroys animal and vegetable life; and, in short, it is by this communication that the science is known and cultivated.

The following observations and experiments on this particular part of the subject we give from Mr. Singer, with a few necessary exceptions, preferring them to any thing we have yet seen for their appropriateness and concise

ness.

59. From the few simple experiments which we have already described the reader must be aware that electricity can be communicated or conveyed from one body to another. But the faculty of electrical transmission is very different in different bodies; some convey it with great rapidity; others more slowly; and there are some that appear absolutely to arrest its progress. Examples of this fact are apparent in the most simple experiments. The divergence of an electrified electrometer may be destroyed, weakened, or maintained, by touching its cap with different bodies; now, as the divergence of the electrometer is caused by its electricity, such effects can only be produced by the relative power of the touching bodies to deprive it thereof; for so long as the electricity remains the divergence will continue unaltered.

60. This may be shown most satisfactorily by the two following experiments. (1.) Touch the cap of the electrified electrometer with a stick of dry glass, sulphur, or sealing-wax; the divergence of its leaves will continue; this shows therefore that these substances do not transmit electricity. (2.) Touch the cap of the electrified electrometer with a piece of wood, a rod of