Part 2 / Book 6 — Book VI (continued 4)

Humboldt informs us that “the most important ancient notice of the relations between lightning and conducting metals is that of Ctesias, in his Indica, Cap. IV. p. 169. He possessed two iron swords, presents from the King Artaxerxes Mnemon, and from his mother Parysatis, which, when planted in the earth, averted clouds, hail and strokes of lightning. He had himself seen the operation, for the king had twice made the experiment before his eyes” (“Cosmos,” Vol. II. N. 186). Ctesias was a man of great learning. He was a contemporary of Xenophon, and lived for a number of years at the Court of Artaxerxes Mnemon as private physician to the king. Diodorus states that Ctesias was highly honoured at the Persian court. An abridged edition of the Indica was printed by Stephens in 1594 (“Hist. Roy. Soc.,” C. R. Weld, London, 1848, Vol. II. p. 93; “La Grande Encyclopédie,” Vol. XIII. p. 536; “Biographie Générale,” Vol. XII. p. 568).

In imitation of Franklin, Doctor Lining, of Charleston, in South Carolina, sent a kite into a thunder cloud, and by that means dissipated the lightning (Philosophical Transactions for 1754, Vol. XLVIII. p. 757).

The opinion entertained by Franklin regarding the nature of electricity differs from that previously submitted by Dufay (A.D. 1733), in the manner shown by Noad at p. 6 of his Manual, London, 1859 edition.

What Dufay considered to be two distinct species of electricities, vitreous and resinous, Franklin conceived to be two different states of the same electricity, which he called positive and negative. This, which constitutes the foundation of the present theory of electricity, is usually called the Franklinian theory, but it can be said to belong equally to Dr. Watson, for he had communicated it to the Royal Society before Franklin’s opinion on the subject was known in England (Phil. Trans. for 1748, Vol. XLV. pp. 49, 491; Thomson, “Hist. Roy. Soc.,” p. 436). Noad, in paragraph 12, applies the latter theory to the case of a charged Leyden jar, alluding to Franklin’s discovery of the location of electricity in the jar, wherefrom is drawn the conclusion that it is upon the glass that the electricity is deposited, and that the conducting coatings serve “only, like the armature of the loadstone, to unite the forces of the several parts and bring them at once to any point desired” (see “Œuvres de Franklin,” trans. of Barbeu-Dubourg, Tome II. p. 16, 3^e lettre).

Of his plus and minus theory, Franklin thus wrote to Mr. Collinson: “To electrise plus or minus no more needs to be known than this, that the parts of the tube or sphere that are rubbed do, in the instant of the friction, attract the electrical fire, and therefore take it from the thing rubbing; the same parts, immediately as the friction upon them ceases, are disposed to give the fire they have received to any body that has less.”

In an appendix to his official report as U.S. Commissioner at the Paris Universal Exposition of 1867, entitled “Franklin and Electrical Semaphores,” Professor Samuel F. B. Morse, LL.D., expressed himself as follows:

“It has frequently been asserted (on what authority I know not) that the first idea of an electric semaphore originated with Franklin. I have sought in vain in the publication of Franklin’s experiments and works for anything confirmatory of this assertion. On mentioning the subject to my friend Professor Blake, he kindly proposed examining the writings of Franklin in order to elicit the truth. From him I have received the following:

“‘I consulted several works for the purpose of ascertaining, if possible, the foundation for the statement that Franklin suggested the idea of semaphores by static electricity. I have not yet found any such suggestion, but I have noted that, following the experiments by Dr. Watson and others, in England, to determine the velocity of the electric discharge, and the time supposed to be required for the electrical discharges across the Thames, by which spirits were kindled, etc. (in 1747), Dr. Franklin (in 1748) made some similar experiments upon the banks of the Schuylkill, and amused his friends by sending a spark “from side to side through the river without any other conductor than the water” (vide Priestley’s “History of Electricity”). This was in 1748, at the end of the year. In 1756 “J. A., Esq.,” of New York (James Alexander), presented to the Royal Society a proposition “to measure the time taken by an electric spark in moving through any given space” by sending the discharge or spark down the Susquehanna or Potomac, and round by way of the Mississippi and Ohio rivers, so that the “electric fire” would have a circuit of some thousands of miles to go. All this was upon the supposition or assumption that the electric fire would choose a continuous water conductor rather than to return or pass through the earth. Franklin presented a paper in reply, in which he says “the proposed experiment (though well imagined and very ingenious) of sending the spark round through a vast length of space, etc. etc., would not afford the satisfaction desired, though we could be sure that the motion of the electric fluid would be in that tract, and not underground in the wet earth by the shortest way”’ (‘Franklin’s Experiments on Electricity, and Letters and Papers on Philosophical Subjects,’ 4to, London, MDCCLXIX, pp. 282, 283).

“Can it be possible that Franklin’s experiment of firing spirits and showing the spark and the effects of the electric discharge across the river originated, or forms the foundation for, the statement that he suggested the semaphoric use of electricity?”

After speaking of the experiments, to which allusion was made (at Watson, A.D. 1745), Franklin writes: “... It is proposed to put an end to them for this season, somewhat humorously, in a party of pleasure, on the banks of the Schuylkill. Spirits at the same time are to be fired by a spark sent from side to side through the river without any other conductor than the water—an experiment which we some time since performed to the amazement of many. A turkey is to be killed for our dinner by the electrical shock, and roasted by the electrical jack, before a fire kindled by the electrified bottle, when the healths of all the famous electricians in England, Holland, France and Germany are to be drank in electrified bumpers under the discharge of guns from the electrical battery.”

It was toward the close of the year 1750 that Franklin entertained the practicability of a lightning conductor (see Winckler, A.D. 1733), and, for this, he says, he was indebted to an experiment made by his friend Mr. Thomas Hopkinson (vide Franklin’s “Complete Works,” London, 1806, Vol. I. p. 172). In his “Poor Richard’s Almanac” for 1753, he refers to the lightning rod as security for “habitations and other buildings from mischief by thunder and lightning.”

References.—J. B. Le Roy, “Lettera al Rozier,” etc., Milano, 1782; “Rec. de Mém. de l’Acad. des Sc.” for 1770 and 1773; Jour. de Phys., 1773, Vol. II; Memoirs of M. Beyer, Paris, 1806–1809, and Delaunay’s explanation of his theories at pp. 193–198 of his 1809 Manuel.

The many notable observations, experiments and discoveries of Franklin are nowhere more ably reviewed than by his great admirer Dr. Priestley, who devotes much space thereto in his justly celebrated work on electricity.

At p. 92 of his “New Experiments,” etc., London, 1774, Franklin alludes to the failure of many European electricians in firing gunpowder by the electric spark, and gives his own method by using a battery of four large glass jars, while at p. 423 of the London edition of his “Letters and Papers,” etc., Franklin relates curious observations which are worth mentioning here. He says that he sent a charge of electricity “through a small glass tube that had borne it well when empty, but when filled with water was shattered to pieces and driven all about the room. Finding no part of the water on the table, I suspected it to have been reduced to vapour. I was confirmed in that suspicion afterward when I had filled a like piece of tube with ink and laid it on a sheet of paper, whereon after the explosion I could find neither any moisture nor any sully from the ink. This experiment of the explosion of water, which I believe was first made by that most ingenious electrician, Father Beccaria, may account for what we sometimes see in a tree struck by lightning, when part of it is reduced to fine splinters like a broom; the sap vessels being so many tubes containing a watery fluid, which, when reduced to vapour, sends every tube lengthways. And, perhaps it is this rarefaction of the fluids in animal bodies killed by lightning or electricity, that by separating its fibres renders the flesh so tender and apt so much sooner to putrefy. I think, too, that much of the damage done by lightning to stone and brick walls may sometimes be owing to the explosion of water found during showers, running or lodging in the joints or small cavities or cracks that happen to be in the walls.”

References.—Majus—May—(Heinrich), “Disp. de fulmine” and “Disp. de tonitru,” Marp., 1673, as at Pogg., Annalen, Vol. II. p. 21; Giuseppe Saverio Poli, “La formazione del Tuono,” etc., 1772, and his other works on the same subject which appeared during the years 1773, 1779 and 1787; Phil. Trans. for 1751, Vol. XLVII. pp. 202, 289, 362; W. de Fonvielle, “Eclairs et Tonnerres”; “Terrestrial Magn.” for June 1903; Jour. of the Franklin Institute for 1836, Vol. XVII., p. 183; M. le Docteur Sestier, “De La Foudre”; “Lightning-Rod Conference,” Reports of Delegates, by G. J. Symons, 1882; Chap. III. s. 3, vol. i. of Van Swinden’s “Recueil,” etc., 1784; Lumière Electrique, Tome XL. No. 23, p. 497; Giovanni Cardan’s work, Lyons, 1663; “Library of Literary Criticism,” C. W. Moulton, Buffalo, 1901–1902, Vol. IV. pp. 79–106; “An Outline of the Sciences of Heat and Electricity,” by Thos. Thomson, London, 1830, pp. 347, 423, 432–433; “The Electrical Researches of the Hon. Henry Cavendish,” Cambridge, 1879, Nos. 350, note, 363; “Works of Benj. Franklin,” Jared Sparks, London, 1882; Phil. Trans., Vols. XLVII. p. 565; XLIX. pp. 300, 305,; L. p. 481; LI. p. 525; LII. 456; also Hutton’s abridgments, Vol. X. pp. 189, 212, 301, 629, 632; Vol. XI. pp. 189, 435, 609; “Bibliothèque Britannique,” Genève, 1796, Vol. LI. p. 393 (letter to M. Marc Auguste Pictet); Stuber, “Continuation of the Life of Dr. Franklin”; “An Essay on the Nature of Heat, Light and Electricity” (on the Franklinian hypothesis), by Chas. Carpenter Bompass, London, 1817, Chap. III. s. 3, p. 217; “List of Books written by or relating to Franklin,” by Paul L. Ford, 1889; L. Baldwin, “Mem. of Amer. Acad.,” O. S. I. part i. p. 257; Sturgeon’s “Researches,” p. 524; J. Bart. Beccari, “De Artif. elect ...”; likewise all the references that are given at pp. 26–27 of Ronalds’ “Catalogue”; “Journal des Savants” for June 1817, pp. 348–356.

A.D. 1752.—Dalibard (Thomas François), French botanist and amateur in physics, carries out very carefully the suggestions embodied in Franklin’s printed letters and constructs an atmospherical conductor at Marly-la-Ville, about eighteen miles from Paris, where Nollet likewise experimented. Dalibard’s apparatus consisted of a pointed iron rod, one inch in diameter and about forty feet long, which was protected from the rain by a sentry box and attached to three long wooden posts insulated by silken strings.

On the 10th of May, 1752, during Dalibard’s absence, an old soldier by the name of Coiffier, who was at the time employed as a carpenter and who had been left in charge, on observing the approach of a storm, hurried to the apparatus prepared to carry out the instructions previously given him. It was not long before he succeeded in obtaining large sparks on presenting a phial to the rod, and these sparks, which were all accompanied by a large snapping noise, were likewise obtained by the curate of Marly, M. Raulet, whom he had sent for and with whose aid Coiffier subsequently succeeded in charging an electric jar. On the 13th of May, Dalibard made, to the French Academy of Sciences, a report of the results thus obtained by Coiffier, to whom, it may be said, properly belongs the distinction of having been the first man who saw the electric spark drawn from the atmosphere.

On the 18th of the same month of May, M. de Lor, of the French University, drew similar sparks from a rod ninety-nine feet high at his house in the Estrapade, at Paris, and the same phenomenon was afterward exhibited to the French King. It is said that the conductor afforded sparks even when the cloud had moved at least six miles from the place of observation. Other experiments of a like nature were made a few days later by Buffon at Montbar, and, during the ensuing months of July and August, in the vicinity of London, by Canton, who, it is said, succeeded in drawing atmospheric electricity by means of a common fishing rod (Dissertation Fifth, Eighth “Britannica,” Vol. I).

An account of the Dalibard and de Lor experiments was transmitted by the Abbé Mazéas, on the 20th of May, to the Royal Society of London.

Mazéas erected, in the upper section of his residence, a magazine consisting of several insulated iron bars connected with the pointed rod. The lightning was brought into the house by means of a projecting wooden pole, having at its extremity a glass tube filled with resin which received a pointed iron rod twelve feet long. This apparatus was, however, too much exposed to afford reliable observations, and Mazéas therefore arranged to make more accurate experiments at the Château de Maintenon, during the months of June, July and October 1753. The results he obtained were communicated to the English Royal Society by Dr. Stephen Hales. The letters of the Abbé Mazéas to the Rev. Stephen Hales, detailing some of M. Le Monnier’s experiments as well as observations made by M. Ludolf at Berlin and transmitted by M. Euler, are to be found at pp. 354–552, Vol. XLVII. Phil. Trans. for 1753. For Mazéas, see also Phil. Trans., Vol. XLVII. p. 534, Vol. XLVIII. part i. p. 377, and Hutton’s abridgments, Vol. X. pp. 289, 434.

Thomas Ronayne in Ireland, and Andrew Crosse[51] in England (see “Account of an apparatus for ascertaining and collecting the electricity of the atmosphere”) made use of long wires in horizontal positions insulated by being attached to glass pillars, but Mazéas, in his Maintenon experiments, attached the iron wire by a silken cord to the top of a steeple ninety feet in height, whence it entered an upper room of the castle, a total distance of 370 feet. With this, Mazéas ascertained that electric effects are produced at all hours of the day during clear, dry and particularly hot weather, the presence of a thunderstorm not being requisite for the production of atmospheric electricity. In the driest summer nights he could discover no signs of electricity in the air, but when the sun reappeared the electricity accompanied it, to vanish again in the evening about half an hour after sunset.

References.—W. Sturgeon, “Lectures,” London, 1842, pp. 182, 183; Phil. Trans., Vol. XLVIII. part i. pp. 370, 377, etc.; Dalibard’s “Franklin,” Vol. II. p. 109, etc.; “Mém. de l’Acad. des Sciences,” for May, 1762; Nollet, “Letters,” Vol. I. p. 9; Franklin’s Works, Vol. V. p. 288; English Cyclopædia, “Arts and Sciences,” Vol. III. pp. 804–805; “Letters of Thomas Ronayne, to Benjamin Franklin,” at p. 137 of Vol. LXII of Phil. Trans., likewise Ronayne both in Journal de Physique, Tome VI, and in the Phil. Trans. for 1772, Vol. LII. pp. 137–140; also Hutton’s abridgments, Vol. XIII. p. 310; Geo. Adams, “Essay on Elect.,” London, 1785, p. 259.

A.D. 1752.—Freke (John), surgeon to St. Bartholomew’s Hospital, London, gives, in the Second Part of “A Treatise ... of Fire,” the third edition of his “Essay to Show the Cause of Electricity,” etc., originally published in 1746, while in the Third Part of the same work he shows the “Mechanical Cause of Magnetism, and why the compass varies in the manner it does.”

He says (pp. 90–91): “It had been impossible that this wonderful Phenomenon of Electricity should ever have been discovered, if there had not been such things as are non-electricable; for, as fast as this Fire had been driven on anything its next neighbour would have carried it farther; but, when it was most wonderfully found, that anything which was suspended on a silk cord (that being non-electricable) was obliged to retain the Fire, which by Electrical Force was driven on it; and when, moreover, it appeared, that any person or thing, being placed on a cake of beeswax (which is also a non-electricable) could no more part with its Fire than when suspended in [sic] a silk cord; I think it will become worthy of inquiry, why they are not electricable.” And, at p. 136, he adds: “I think it a great pity that the word Electricity should ever have been given to so wonderful a Phenomenon, which might properly be considered as the first principle in nature. Perhaps the word Vivacity might not have been an improper one; but it is too late to think of changing a name it has so long obtain’d.” In the Third Part, he explains that “by the Fire passing from and to the Sun, it so pervades iron aptly placed, as to make it attractive and produce the various operations of magnetism.”

Reference.—“Gentleman’s Magazine,” London, Vol. XVI for 1746, pp. 521, 557.

A.D. 1752.—In this year was published at Leipzig the “Biblia Naturæ,” written by John Swammerdam, a celebrated Dutch natural philosopher (1637–1682), all of whose works were translated into English and published in folio during the year 1758.

In the second volume of the Biblia, he thus alludes to one of many experiments made by him in 1678, before the Grand Duke of Tuscany: “Let there be a cylindrical glass tube in the interior of which is placed a muscle, whence proceeds a nerve that has been enveloped in its course with a small silver wire, so as to give us the power of raising it without pressing it too much or wounding it. This wire is made to pass through a ring bored in the extremity of a small copper support and soldered to a sort of piston or partition; but the little silver wire is so arranged that on passing between the glass and the piston the nerve may be drawn by the hand and so touch the copper. The muscle is immediately seen to contract.”

Through Swammerdam, the Germans lay claim to the origin of what has been called galvanism. It certainly cannot be denied that the above-described experiment closely resembles that which made Galvani famous (A.D. 1786).

References.—Swammerdam’s Biography, also Dissertation Fifth, in the eighth edition “Encycl. Brit.”; the note at p. 491 of Ronalds’ “Catalogue”; “Gen. Biog. Dict.,” London, 1816, Vol. XXIX. pp. 45–47; Eloy, “Dict. Hist. de la Méd.,” Vol. IV; “Biog. Générale,” Vol. XLIV. pp. 706–708; Cuvier, “Hist. des Sc. Naturelles,” Vol. II. pp. 427–433; Schelhorn, “Amænitates liter.,” Vol. XIV; “Biblioth. Hulthemiana,” Gand, 1836, Vol. II; Boerhaave, Preface to “Biblia Naturæ.”

A.D. 1752.—On the 16th of April, 1752, is read before the Royal Society a letter written by John Smeaton, a very prominent English engineer and inventor (1724–1792), to Mr. John Ellicot, giving an account of the electrical experiments in vacuo made with his improved air pump at the request of Mr. Wilson. This account, fully illustrated, appears in the Society’s Vol. LXVII for the years 1751 and 1752, pp. 415–428.

He observes that, upon heating the middle of a large iron bar to a great heat, the hot part can be as strongly electrified as the cold parts on each side of it. He also finds that if anybody who is insulated presses the flat part of his hand heavily against the globe, while another person standing upon the floor does the same, in order to excite it, the one who is insulated will hardly be electrified at all; but that, if he only lays his fingers lightly upon the globe, he will be very strongly electrified.

References.—Wilson, “Treatise on Electricity,” pp. 129–216; Phil. Trans. XLVI. p. 513; “Dict. of Nat. Biography,” Vol. LII. pp. 393–395; “Biog. Univ.” (Michaud), Vol. XXXIX. p. 445; Smile’s “Lives of the Engineers—Smeaton and Rennie”; Flint’s “Mudge Memoirs,” Truro, 1883.

A.D. 1752–1753.—M. de Romas, Assessor to the Presideal of Nerac, in France, repeats the experiment of Benjamin Franklin, and succeeds finally in bringing from the clouds more electricity than had before been taken by any apparatus.

He constructed a kite seven feet five inches high and three feet wide, with a surface of eighteen square feet, and, having wound fine copper wire around a strong cord through its entire length of about eight hundred feet, he raised the kite to a height of five hundred and fifty feet on the 7th of June, 1753. Sparks two inches in length were at first drawn by a discharging rod, and, when the kite was afterwards allowed to reach an elevation of six hundred and fifty feet, he received many flashes one foot long, three inches wide and three lines diameter, accompanied by a noise audible at as great a distance as five hundred feet.

On the 16th of August, M. de Romas raised the kite with about one thousand feet of string and obtained thirty beams of fire, nine or ten feet long and about an inch thick, accompanied by a noise similar to that of a pistol shot (“Encycl. Britannica,” eighth edition, Vol. VIII. p. 582). Three years later, August 26, 1756, and also during the year 1757, De Romas obtained similar results from numerous experiments. He finally apprehended much danger from the raising of the kite and thereafter coiled the string upon a small carriage, which he drew along by means of silken lines as the cord was being unwound.

The researches of De Romas concerning the electricity of isolated metallic bars are embraced in six letters addressed by him to the Bordeaux Academy of Sciences between July 12, 1752, and June 14, 1753. It is reported that they have never been printed and that they are kept, together with other manuscript matter of the same physicist, in the private archives of the institution.

The experiments of De Romas upon isolated bars were first repeated by Boze at Wittenberg, by Gordon at Erfurt, and by Lomonozow in Russia (Phil. Trans., Vol. XLVIII. part ii. p. 272). M. Veratti, of Bologna, obtained the electric spark in all weathers, through a bar of iron resting in sulphur, and Th. Marin, of the same city, by means of a long iron pole erected upon his dwelling, studied the relationship of rain and atmospheric electricity (Musschenbroek, “Cours de Physique” Vol. I. p. 397).

References.—Journal des Sçavans for October, 1753, p. 222; “Mémoire sur les moyens,” etc., par De Romas, Bordeaux, 1776; Sturgeon’s “Annals,” etc., Vol. V. p. 9; Harris, “Electricity,” p. 176; Priestley, “History,” etc., 1775, pp. 326–329; “Mémoires de Mathématique,” etc., Vol. II. p. 393, and Vol. IV. p. 514; “Etude sur les travaux de De Romas,” p. 491, by Prof. Mergey, of Bordeaux, which latter work won a prize for its author in 1853; Becquerel, “Traité expérimental,” etc., 1834, Vol. I. pp. 42–43; likewise the results obtained by Prof. Charles in “Traité de Physique Expérimentale,” etc., par Biot, Paris, 1816, Vol. II. pp. 444, 446, and in Peltier’s Introduction to his “Observations et Recherches Expérimentales,” etc., Paris, 1840, p. 7, as well as Brisson’s “Dict. de Phys.,” Paris, 1801, Vol. II. p. 174, and “Mémoires des Savants Etrangers,” 1755, Vol. II. p. 406.

A.D. 1753.—M. Deslandes, member of the French Royal Academy of Sciences, is the author of “Recueil de Différents traités de Physique,” the third volume of which contains his memoir on the effects of thunder upon the mariner’s compass. He alludes to the observations made thereon by Dr. Lister of London (well known by his “Historiæ Animalium Angliæ,” Lugd., 1678), as well as to many experiments made by Musschenbroek and by others noted in the Philosophical Transactions.

A.D. 1753.—Prof. George William Richmann (1711–1753), native of Sweden and member of the Imperial Academy of St. Petersburg, who had already constructed an apparatus for obtaining atmospherical electricity according to Franklin’s plans, was attending a meeting of the Russian Academy of Science, on the 6th of August, 1753, when his ear caught the sound of a very heavy thunder clap. He hastened away in company with his engraver, M. Sokolow, and upon their arrival home they found the plummet of the electrometer elevated four degrees from the perpendicular. Richmann stooped toward the latter to ascertain the force of the electricity, and “as he stood in that posture, a great white and bluish fire appeared between the rod of the electrometer and his head. At the same time a sort of steam or vapour arose, which entirely benumbed the engraver and made him sink on the ground.” Sokolow recovered, but Richmann had met with instant death.

References.—“Library of Useful Knowledge,” London, 1829; “Electricity,” p. 59, also p. 33; “Lettre sur la mort de Richmann,” par C. A. Rabiqueau, Paris, n. d.; “Comment. Acad. Petrop.,” XIV. pp. 23, 301–302, also the “Novi Comment.,” IV. pp. 25, 235 and 299; “Biog. Générale,” Vol. XLII. p. 258; “Gentleman’s Magazine,” London, Vol. XXIII., 1753, p. 431 and Vol. XXV. for 1755, p. 3; Singer, “Electricity,” p. 217; Harris, “Electricity,” p. 177; Phil. Trans., Vol. XLVIII. part ii. pp. 763–765, 772; also Vol. XLIX. part i. pp. 61, 67, and the abridgments by Hutton, Vol. X. pp. 525, 574–577; “La physique à la portée de tout le monde,” par le Père Paulian, Vol. II. p. 357; “Hist. de l’Acad. des Sciences,” pour 1753, p. 78; “Franklin in France,” 1888, Part. I. p. 5.

A.D. 1753.—Canton (John), an English savant (1718–1772), announces his most important discovery that vitreous or resinous electricity may be produced at will in the same tube. This he proves on taking a tube, which had been roughened by grinding it with thin sheet-lead and flour-of-emery mixed with water, and which developed vitreous electricity when rubbed with dry oil silk, and resinous or negative electricity when rubbed with new flannel. Rough quartz will, it is said, show like results. He also took a tube, of which only one-half had been made rough while the other half was polished, and he demonstrated that the different electricities are produced at a single stroke with the same rubber.

He likewise discovered that the exciting power of the rubber or cushion of the electrical machine will be very greatly increased by applying to it an amalgam of mercury and tin mixed with a little chalk or whiting (see Winckler, at A.D. 1733, for the introduction of the cushion).

His very remarkable experiments upon many descriptions of tourmaline, reported to the Royal Society in December 1759, were followed by many others detailed by Priestley, at pp. 298–301 of his “History of Electricity,” London, 1775, and Canton was the first to discover the electrical properties of the topaz, which latter were made known during the early part of the year 1760. (Consult Wilhelm Hankel, “Uber die therm. eigen. des Topases,” Leipzig, 1870.)

He was also the first to establish properly the fundamental fact of electrification by induction, or, as he terms it, “relating to bodies immerged in electric atmospheres,” which afterward led Wilcke (A.D. 1757) and Æpinus (A.D. 1759) to the method of charging a plate of air like a plate of glass, and to make the most perfect imitation of the phenomena of thunder and lightning (George Adams, “Essay on Electricity,” London, 1799, pp. 351–356; Noad, “Manual,” Chapter I, and Priestley, “History,” etc., s. 5). The paper containing an account of Canton’s experiments was read before the Royal Society, December 6, 1753. The principle enounced is that “the electric fluid, when there is a redundancy of it in any body, repels the electric fluid in any other body when they are brought within the sphere of each other’s influence and drives it into the remote parts of the body; or quite out of it, if there be any outlet for that purpose. In other words, bodies immerged in electric atmospheres always become possessed of the electricity contrary to that of the body in whose atmosphere they are immerged.”

Canton is the first to show that the air of a room can be electrified either positively or negatively, and can be made to retain the electricity when received. He thus explains his method: “Take a charged phial in one hand and a lighted candle insulated in the other, and, going into any room, bring the wire of the phial very near to the flame of the candle and hold it there about half a minute, then carry the phial and candle out of the room and return with the pith balls (suspended by fine linen threads) held out at arm’s length. The balls will begin to separate on entering the room and will stand an inch and a half or two inches apart when brought near the middle of it.”

The construction of artificial magnets by Canton, through the combination of the Duhamel (A.D. 1749) and the Michell (A.D. 1750) methods, as well as without the aid of natural loadstones or artificial magnets, is detailed by Noad at Chapter XV of his “Manual,” London, 1859.

References.—Phil. Trans., Vol. XXXV. p. 137 (Berlinghieri, V. L.); Vol. XXXVII. p. 294 (Marcel, A.); Vol. XLVII. p. 31; Vol. XLVIII. part i. pp. 350, 356, and Part II. pp. 780, 782 and 784, also Vol. XLIX. part i. p. 300; Vol. LI. pp. 398, 403, and Vol. LII. part ii. pp. 457, 461; and the abridgments of Hutton, Vol. X. pp. 131, 421, 532; Vol. XI. pp. 421, 609; A.D. 1722, and A.D. 1752; “A Course of Lectures on Nat. Philos. and the Mechanical Arts,” by Thos. Young, London, 1807, Vol. I. p. 372; II. pp. 64, 243; “The Electrical Researches of Hon. Hy. Cavendish,” 1879, Nos. 117, 205; Descriptions and Drawings of the various electric friction machines can be seen in Priestley’s “History,” Plates IV-VIII, and in Albrecht’s “Geschichte d. Electricität,” 1885, pp. 20–30; Acta Acad. Petr., I., 1778; “Gentleman’s Magazine” for Sept. 1759. See likewise the Phil. Trans. for Monday, January 21, 1666, p. 375, and George Adams’ “Essay on Electricity,” etc., London, 1799, p. 579, for method of making the artificial Bolonian stone or Canton’s phosphorus.

A.D. 1753.—Beccaria (Giovanni Baptista) (1716–1781), a very ingenious and industrious Italian electrician and astronomer, is the author of several quite important works on electricity.

Father Beccaria, as he is sometimes called from having been a member of the religious order of the Pious Schools, proved at the time to be the most indefatigable follower of Franklin in the study of atmospheric electricity. He was the first who recorded the phenomena of thunderstorms, and his many observations thereon are detailed throughout Part I. period x. and s. 10 of Priestley’s great work on electricity. Beccaria says that all clouds, whether of thunder, rain, snow or hail, are formed by the electric fluid; that the electric matter is continually darting from the clouds in one place at the same time that it is discharged from the earth in another; and that the clouds serve as conductors to convey the electric fluid from those places of the earth which are overloaded with it to those which are exhausted of it. Having shown that the polarity of the magnetic needle is determined by the direction in which the electric current has passed through it, he suggests taking the polarity acquired by ferruginous bodies as a test for ascertaining the kind of electricity with which the thunder cloud is charged.

He also shows that the meteor called a falling star is an electrical appearance, explains the cause of the peculiar noise attending the electric spark, and states that the passage of electricity is not instantaneous through the best conductors. He found a spark to occupy at least half a second in passing through 500 feet of wire, and six and a half seconds through a hempen cord of the same length, although when the cord was dampened it passed through it in two or three seconds.

He was the first to show the electric spark while in its passage through water, and he observed that the water sank in the tubes whenever a spark passed from one to the other as the air was repelled by the electric fluid. He found the effect of the electric spark upon water greater than the effect of common fire on gunpowder, and says he does not doubt that, if a method could be found of managing them equally well, a cannon charged with water would be more effective (“dreadful”) than one charged with gunpowder.

He demonstrates that air, contiguous to an electrified body, gradually acquires the same electricity; that the electricity of the body is diminished by that of the air; that there is mutual repulsion between air and the electric fluid, and that the latter, in passing through any portion of air, creates a temporary vacuum.

The production of what he calls his new inventive phosphorus and the method he employs for revivifying metals, are described, respectively, at pp. 365 and 282 of his “Lettere dell’ elettricismo.”

References.—Beccaria, “Lettere,” etc., Bologna, 1758, pp. 146, etc., 193, 266, 268, 290, 310, 345; likewise his “Elettricismo Artificiale,” Turin, 1753, pp. 110, 114, 227; Phil. Trans. for 1760, Vol. LI. p. 514; 1762, p. 486; 1766, Vol. LVI. p. 105; 1767, Vol. LVII. p. 297; 1770, Vol. LX. p. 277; 1771, p. 212, also Hutton’s abridgments, Vol. XI. p. 435; Vol. XII, pp. 291, 445; Vol. XIII. p. 50; Wartmann, “Mém. sur les Etoiles filantes”; Humboldt, “Relation historique,” Tome I; Lardner, “Lectures,” Vol. I. pp. 429–444; Sturgeon’s Annals, Vol. VI. pp. 415–420, 425–431, and Vol. VIII. p. 180; Noad, “Manual,” London, 1859, p. 197; Louis Cotte, “Observation ...” Paris, 1769 and 1772; “Mém. de Paris” for the same years and Jour. de Phys. for 1783; Ant. Maria Vassalli-Eandi, “Notizia sopra la vita ... di Beccaria,” 1816; Carlo Barletti, “Nuove Sperienze ...” Milano, 1771; “Biog. Générale,” Vol. V. pp. 77–78; “The Electrical Researches of Hon. Henry Cavendish,” Cambridge, 1879, No. 136; Hale, “Franklin in France,” Boston, 1888, Part I. p. 447; Humboldt, “Cosmos,” London, 1859, Vol. I. pp. 113–136, 202, 337; Vol. V. pp. 217–219, for the observations of Beccaria, Rozier, Kepler, Benzenberg, Brandes, Bogulawski, Nicholson, Arago and others on atmospheric electricity, aerolites, etc. See likewise Beccaria’s letters to Jean Claude Fromond, the Italian physicist (1703–1795), relating his experiments tending to prove that electric motions do not occur in vacuo, also his letters to the Princess Giuseppina di Carignano on the electricity of the moon, as well as to Jean Baptiste Le Roy and to Jacopo Bartolommeo Beccari relative to experiments with his kite; “Scelta di Opuscoli,” of Amoretti, Campi, Fromond and Soave, Vols. XIX. XXI. XXXII.; “Opuscoli Scelti,” II. 378; III. 243, 284, 377; V. 19.

A.D. 1753.—Bazin (Gilles Augustin), French physician and naturalist, publishes, at Strasbourg, an illustrated treatise on Magnetic Currents (“Description des Courants Magnétiques,” etc.), which also contains his observations upon the magnet, and a supplement to which appears during the year 1754.

References.—“La Grande Encyclopédie,” Vol. V. p. 974; Michaud, “Biog. Univ.,” Vol. III. p. 353; Ninth “Britannica,” Vol. XV. p. 242.

A.D. 1753.—C. M., i. e. Charles Morrison and not Charles Marshall, of Greenock, Scotland, writes, from Renfrew, February 1, 1753, to the Scots’ Magazine, a letter entitled “An Expeditious Method of Conveying Intelligence,” wherein is first suggested a practical manner of transmitting messages by frictional electricity.

A full copy of this letter appears at pp. 7–9 of Robert Sabine’s “Electric Telegraph,” London, 1872, and at p. 9, 103, No. 570, of the Scientific American Supplement for December 4, 1886, the last-named also reproducing some correspondence establishing the identity of Charles Morrison which was found in the papers of Sir David Brewster.

In the article of Auguste Guérout, which appeared in La Lumière Electrique early in 1883, C. M. is alluded to as Charles Marshall. This is likewise the case in Johnson’s Encyclopædia, 1878, Vol. IV. p. 757. Fahie gives (“History of the Electric Telegraph,” London, 1884, pp. 68–77) a full account of the many inquiries instituted to establish the identity of C. M., which he admits to stand for Charles Morrison, although, at p. 81 of the same work, is given a letter of Sir Francis Ronalds alluding to Charles Marshall, of Renfrew. An article in Cornhill Magazine, Vol. II for 1860, pp. 65–66, speaks of an elderly Scotch lady who remembered a very clever man named Charles Marshall, who could make “lichtnin’ write an’ speak” and who could “licht a room wi’ coal-reek” (coal-smoke).

In his remarks upon the afore-named letter, made during the year 1859, Sir David Brewster says: “Here we have an electric telegraph upward of a hundred years old, which at the present day would convey intelligence expeditiously, and we are constrained to admit that C. M. was the inventor of the electric telegraph.... Everything done since is only improvement.”

References.—Scots’ Magaz., XV. p. 73; “Le Cosmos,” Paris, Feb. 17, 1854; “Dict. of Nat. Biog.,” Vol. XXXIX. p. 107; Athenæum of Nov. 5, 1864; Lesage, at A.D. 1774; Th. Du Moncel, “Exposé des applications de l’électricité,” Paris, 1874, Vol. III. pp. 1 and 2.

A.D. 1754.—Diwish (Prokop), Diviss—Divisch (Procopius), a monk of Seuftenberg, Bohemia (1696–1765), erects, June 15, 1754, a lightning protector upon the palace of the curator of Prenditz, Moravia. The apparatus was composed of a pole surmounted by an iron rod supporting twelve curved up branches and terminating in the same number of metallic boxes filled with iron ore and closed by a boxwood cover traversed by twenty-seven sharp iron points which plunged at their base in the ore. All the system of wires was united to the earth by a large chain. The enemies of Diwish, jealous of his success at the court of Vienna, excited the peasants of the locality against him, and, under the pretext that his lightning rod was the cause of the great drought, they made him take down the lightning rod which he had utilized for six years and then imprisoned him. What is most curious is the form of this first lightning rod, which is of multiple points, like the one M. Melseu afterward invented.

References.—Poggendorff, Vol. I. p. 580, for Procopius Divisch’s “Erfand einen Wetter Ableiter”; Scientific American, Sept. 10, 1887, p. 160; “Kronika Prace,” by Pokorny, of Prague; “Historical Magazine,” Feb. 1868, Art. XII. p. 93; “Prague News,” for 1754, art. of Dr. Scrinci.

A.D. 1754.—Ammersin (Rev. Father Windelinus), of Lucerne, Switzerland, announces in his “Brevis relatio de electricitate,” etc., that wood properly dried till it becomes very brown is a nonconductor of electricity. We have already mentioned the observation made by Benjamin Wilson (A.D. 1746) that, when a dry, warm piece of wood is broken across, one of the pieces becomes vitreously and the other resinously electrified.

Ammersin advises boiling the dried wood in linseed oil or covering it with varnish to prevent the possible return of moisture, and he states that wood thus treated seems to afford stronger appearances of electricity than does even glass (Phil. Trans., Vol. LII. part i. p. 342).

References.—Ammersin, “Kurze Nachricht,” etc., pub. at Basel, 1771, and translated the same year by Jallabert, who embodied it in his “Versuche über die Elektricität,” etc.

A.D. 1754.—In his “Dissertations sur l’incompatibilité de l’attraction,” etc., Le Père Gerdil, Professor of Philosophy in the Royal University of Turin, speaks of agencies of which we shall never know anything and of others with which we shall inductively become acquainted, although we shall always ignore many of their respective quantities, qualities and differences. He says that the electric fluid explains the sympathy known to exist between amber and straws—shown by the analogy observed between electricity and magnetism to be the same as that existing between iron and the loadstone.

A.D. 1754.—Mr. Strype produces the sixth and last edition of the original “Survey of London” by John Stow, which first appeared during the year 1598.

In his account of Cornehill Ward, allusion is made to the “fair new steeple” of the Church of Saint Michael th’ Archangel, “begun to be built in the year 1421,” and, at p. 74, occurs the following: “As I have oft heard my father report, upon St. James’ night, certain men in the loft next under the bells, ringing of a peal, a tempest of lightning and thunder did arise, an ugly shapen sight appeared to them, coming in at the South window and lighted on the North, for fear whereof they all fell down and lay as dead for the time, letting the bells ring and cease of their own accord; when the ringers came to themselves, they found certain stones of the North window to be razed and scratched, as if they had been so much butter, printed with a lion’s claw; the same stones were fastened there again and so remain to this day.”

In one of the notes to William T. Thoms’ reprint of the above-named “now perfectly invalyable” work, he says: “It is quite clear from the tone in which Stow speaks of this ‘ugly shapen sight’ and the marks ‘printed with a lion’s claw,’ that he suspected this instance of the power of the electric fluid to be nothing less than a visitation from the foul fiend himself.”

Speaking of St. Paul’s Cathedral, Stow tells us that its pulpit cross “was by tempest of lightning and thunder defaced,” and that “on Wednesday, the fourth of June (in the year 1561), betweene three, four and five of the clock, in the after-noone, the steeple of Paule’s in London, being fired by lightning brast forth (as it seemed to the beholders) two or three yards beneath the foote of the crosse, and from thence burnt downe the speere to the stone worke and bels, so terribly, that within the space of foure houres, the same steeple with the roofes of the church ... were consumed.” Very curious and interesting reading will be found in the “Burnynge of Paule Church, London, in 1561, and the iiii day of June, by lyghtnynge at three of the clocke ...” by Wyllyam Seres, London, 1563; as well as in his previous work on like subject, published in 1561. See Report in “Archæologia,” London, 1794, Vol. XI. pp. 72–86; likewise the entry at A.D. 1769, relative to another lightning stroke in 1772.

Stow is perhaps best known by his “Annales, or a Generalle Chronicle of England.” In that portion of the latter work devoted to “the life and raigne of Queene Elizabeth” he states (London ed., 1631, p. 809) “that the knowledge and use of the sea compasse or needle was neither familiar nor understood but few yeeres before” the time of the navigators John Hawkins, Francis Drake, Martin Frobisher and Thomas Candish, and he adds (at p. 810) “that the honour of that invention, as touching the propertie of the Magneticall needle in pointing towards the Poles is attributed by (Flavius) Blondus in his Italia Illustrata (in the description of Campadia Felix) and by the great writer Paulus Jovius in lib. xxv. of his History in the end [sic], to the citizens of Amalfi.... The author’s name is no more particularly recorded, then [sic] to be one Flavio ... for to him that honour is given by Francis Lopez, of Gomara, in his West Indian History, lib. i. cap. 9, and by Peter Ciezius, in lib. ii. cap. 9, of his Indian Story, and by Pandulph: Collenutius in his History of Naples, who, three hundred yeeres since, namely in the yeere of our Saviour 1305, discovered that propertie in the Magnes and applied it to navigation” (see, for Flavius Blondus: George Hakewill, “An apologie,” etc., Oxford, 1635, lib. iii. s. 4, and lib. v. p. 60; “Blondi Flavii Fortiriensis ... Italia Illustrata,” 1531, folio; Flavius Blondus (Flavio Biondo), “Roma Ristaurata et Italia Illustrata,” Vinezia, 1558, 12mo; Niceron, “Mémoires ... des hommes illustres,” Paris, 1731, Vol. XVI. pp. 274–281).

A contemporary of Flavius Blondus, by name Michael Angelus Blondus (1497–1560), author of “De Ventis et Navigatione,” published at Venice in 1546, likewise alludes to the polarity of the needle, and gives a curious illustration of a mariner’s compass at Chap. XXIV. p. 15, of the last-named work. (For M. A. Blondus, see “La Grande Encyclopédie,” Vol. VI. p. 899.)

Stow makes reference (p. 810) to Dr. Gilbert’s De Magnete, to the “diuision of the plot or playne of the compasse into the thirty-two points,” considered by “Goropius in his lib. iii. De Origin. Hispanicis, to have been the inuention of some Germane,” and to the manner and “meanes saylers vsed to sayle, before they atteined the knowledge of the compasse.”

A.D. 1755.—Eeles—Eales (Henry), a prominent scientist of Lismore, Ireland, communicates to the Royal Society, on the 25th of April, 1755, a paper concerning the electrical property of steam and exhalations of all kinds. Eeles’ theory of the electricity of vapour (“On Vesicles and Atmospheres of Electricity”), afterward developed by Sir John Herschel, is fully explained in the “Encycl. Brit.” article on “Meteorology” (par. 135, etc.), and is also alluded to at p. 43 of Harris’ “Electricity” as well as at p. 153, Vol. XLIX. part i. of the Philosophical Transactions.

Mr. Eeles showed, that while the Leyden jar is being charged, both the inside and the outside have the same kind of electricity and that the negative electricity does not appear until the machine has ceased turning. Eeles’ hypothesis, extracted from his “Philosophical Essays,” and from the analysis of a course of lectures delivered at Trinity College, Cambridge, by Mr. Atwood, is treated of at length by George Adams in the fourth chapter of his “Essay on Electricity,” wherein pertinent allusion is also made to the fact of Mr. Eeles having been purposely shut out of Priestley’s “History and Present State of Electricity.”

References.—Philosophical Transactions, Vol. XLVII. p. 524; Phil. Mag. and Journal, Vol. XLIV. p. 401 (1814).

A.D. 1756.—Le Chevalier Jacques C. F. de la Perriere de Roiffé (not Reiffé) is the author of “Méchanismes de l’Electricité et de l’Univers,” published at Paris, wherein he pretends to account for all electrical phenomena.

At p. 12 of his Préface, he curiously states that as everybody comprehends the distinction between elastic and non-elastic bodies, likewise the existence, nature and diversity of the properties of atmospheric fluids, with which all bodies are impregnated and by which they are surrounded, also the various expansive modes of activity to which they are subject, as well as their immiscibility as regards the surrounding air, without which latter they could not, however, subsist, he will in his new theory apply these principles to the mechanisms of electricity and of the universe as affected by the general laws and the invariable results attaching to shock and motion.

A.D. 1756.—In the “Subtil Medium Proved,” etc., of Mr. R. Lovett, lay-clerk of the cathedral church at Worcester, England, are shown numerous medical cures successfully made by electricity. He asserts that the electric fluid is almost a specific in all cases of violent pains, like obstinate headache, the toothache, sciatica, etc., but that it has not succeeded so well in rheumatic affections. He states that electricity properly administered has never caused injury, and he alludes to equally successful cures made by the Rev. John Wesley and by Dr. Wetzel, of Upsal.

The well-known physician, Antonius de Haen, during several years’ experience, made many cures of paralysis, St. Vitus’ dance, etc., by the agency of electricity, as related in his Ratio Medendi, Vol. I. pp. 199, 200, 233, 234 and 389. Allusion has been made in these pages to the employment of electricity for medical purposes by Kratzenstein (A.D. 1745) and by Jallabert (A.D. 1749), and Priestley named many others who have likewise used it successfully in their practice.

References.—“Subtil Medium Proved,” etc., pp. 76, 101 and 112; also his “Philosophical Essays,” Worcester, 1761 and 1766, and his “Electrical Philosopher,” 1774; Wesley’s “Desideratum, or Electricity made Plain and Useful,” p. 3; Joseph Veratti, “Observations ... pour guérir les paralytiques....” La Haye, 1750.

A.D. 1757.—Dr. Darwin, of Lichfield, addresses to the Royal Society of London a paper which is read May 5, 1757, and in which he gives an account of experiments to prove that the electric atmosphere does not displace air, and that all light, dry, animal and vegetable substances, in particular, are slow to part with the electricity with which they have been charged (Phil. Trans., Vol. L. part i. pp. 252 and 351).

A.D. 1757.—Euler (Leonard), a native of Switzerland, who studied under the Bernoullis, and who succeeded Daniel Bernoulli as Professor of Mathematics at St. Petersburg, was undoubtedly one of the greatest analysts the world has ever produced (“Encycl. Brit.,” Fifth Dissertation of the eighth edition, Vol. I. p. 742).

He adopted the theory of Descartes that the magnetic fluid moves from the equator to the poles, and he endeavoured to determine mathematically the course of the magnetic needle over the earth’s surface. He announces that “the magnetic direction on the earth follows always the small circle which passes through the given place and the two magnetic poles of the earth,” or, as worded by Sir David Brewster, that “the horizontal needle is a tangent to the circle passing through the place of observation and through the two points on the earth’s surface where the dipping needle becomes vertical or the horizontal needle loses its directive power.”

He entertained very peculiar ideas regarding the source of power in the loadstone, the pores of which he imagined were filled with valves admitting of the entrance of the current and preventing its return. His notions on this subject are best given in his own words: “Non-magnetic bodies are freely pervaded by the magnetic matter in all directions; loadstones were pervaded by it in one direction only ... water, we know, contains in its pores particles of air ... air, again, it is equally certain, contains in its pores a fluid incomparably more subtile, viz. æther, and which, on many occasions, is separated from it, as in Electricity; and now we see a still further progression, and that ether contains a matter much more subtile than itself—the magnetic matter which may, perhaps, contain in its turn others still more subtile.... The loadstone, besides a great many pores filled with ether, like all other bodies, contains some still much more narrow into which the magnetic matter alone can find admission. These pores are disposed in such a manner as to have communication with each other, and constitute tubes or canals through which the magnetic matter passes from the one extremity to the other. Finally, this matter can be transmitted through these tubes only in one direction, without the possibility of returning in the opposite direction.... As we see nothing that impels the iron toward the loadstone, we say that the latter attracts it. It cannot be doubted, however, that there is a very subtile, though invisible matter, which produces this effect by actually impelling the iron towards the loadstone.”

References.—“Journal des Savants” for March and April 1868; Euler’s “Letters,” translated into English, 1802, Vol. I. p. 214, and Vol. II. pp. 240, 242, 244; “Berlin Memoirs,” for 1746, p. 117; 1757, p. 175; 1766, p. 213; Poggendorff, Vol. I. p. 702; “Nova Act. Petropol.” for 1779, Vol. III; “Pièces de Prix de l’Acad. des Sc. de Paris,” Vol. V. Mém. II and IX, this last-named publication, containing likewise a joint Memoir of D. Euler, J. Bernoulli and E. F. Dutour upon the mariner’s compass, which appeared in Paris during 1748; Whewell, “History of the Inductive Sciences,” 1859, Vol. I. pp. 225, 367, 370; Vol. II. pp. 32, 40.

His son, Albert Euler, censured Halley’s magnetical hypothesis, and proposed, in 1766, a theory requiring the assumption of only two poles, distinct, however, from those of the terrestrial axis.

A.D. 1757.—Dollond (John), who was at first a silk weaver at Spitalfields, England, which occupation he abandoned in order to give his exclusive attention to scientific experimental studies, discovered the laws of the dispersion of light and constructed the first achromatic telescope as well as several improved instruments for magnetic observations. A full description of the most important of these, accompanied by illustrations, can be found in the articles of the “Encyclopædia Britannica” on magnetic instruments.

References.—Kelly’s “Life of John Dollond,” London, 1808; Phil. Mag., Vol. XVIII. p. 47; Thomas Thomson, “Hist. of Roy. Soc.,” London, 1812, pp. 379–382; “Directions for using the Electric Machine made by P. and J. Dollond,” London, 1761.

A.D. 1757.—Wilcke (Johann Karl), a very distinguished scientist of Stockholm (1732–1796), introduces new phenomena respecting the production of electricity produced by melting electrical substances, which he discovers in continuation of experiments begun by Stephen Grey. He gives the name of spontaneous to the electricity produced by the liquefaction of electrics, observing that the electricity of melted sulphur does not appear until it commences to cool and to contract, its maximum being reached at its point of greatest contraction. Melted sealing wax, he says, becomes negatively electrified when poured into glass, but, when poured into sulphur, it is positively electrified, leaving the sulphur negative (Sir Humphry Davy, “Bakerian Lectures,” London, 1840, p. 36 and notes).

While in Berlin, he and Æpinus investigate the subject of electric atmospheres, and they are led to the discovery that plates of air can be charged in the same manner as plates of glass. (See Canton, A.D. 1753.) This they did by suspending large wooden boards, which were covered with tin and whose flat surfaces were held parallel to and near each other. They found that upon electrifying one of the boards positively the other was always negative, and that with them could be given shocks like those produced by a Leyden jar. They likened the state of the boards to the condition of the clouds and the earth during a thunderstorm, the earth being in one state and the clouds in the opposite, the body of air between them answering the same purpose as the small plate of air between the boards or the plate of glass between the two metallic coatings of the Leyden jar.

In Wilcke’s treatise, alluded to below, he defines the two electricities much more clearly than had previously been done. He distinguishes three causes of excitation, viz. warming, liquefaction and friction; the spontaneous electricity already alluded to, he further says, is the result of the apposition or mutual action of two bodies, in consequence of which one of them is electrified positively and the other negatively; communicated electricity, on the other hand, is that which is superinduced upon the whole or part of a body, electric or non-electric, without the body having been previously heated, melted or rubbed, or without any mutual action between it and any other body. This distinction is, in general, very obvious, but Mr. Wilcke defines it throughout his work in a very clear manner, citing cases wherein they are frequently confounded.

Wilcke and Anton Brugmans (A.D. 1778) first propounded the theory of two magnetic fluids, which was afterward established by Coulomb (A.D. 1785) and perfected by the great mathematician Poisson (A.D. 1811). The hypothesis of the two fluids supposes that a magnet contains minute invisible particles of iron, each of which possesses by itself the properties of a separate magnet. It is assumed that there are two distinct fluids—the austral and the boreal—which reside in each particle of iron. These fluids are inert and neutral when combined, as in ordinary iron, but when they are decomposed the particles of the austral attract those of the boreal, and vice versa, while they each repel one another.

References.—Wilcke, “Disputatio inauguralis physica,” etc., published Rostock, 1757, also his “Herrn Franklin’s briefe von der electricitat,” etc., Leipzig, 1758, his “Jal om Magneten,” 1764, and his “Über den Magneten,” Leipzig, 1758; besides 1794–1795; likewise his different Memoirs in the “Swedisches Musæum,” Vol. I. p. 31, and in both the “Schwedischen Akad. Abhandlungen,” etc. (also Neue Abhand.) and the “Vetensk Acad. Handl.” for 1758, 1759, 1761–1763, 1766–1770, 1772, 1775, 1777, 1780, 1782, 1785, 1786, 1790; “The Electrical Researches of Hon. Hy. Cavendish,” 1879, No. 134.

A.D. 1759.—Hartmann (Johann Friedrich), of Hanover, is the author of three works on electricity, published in that city during 1759, 1764 and 1766, wherein he gives an account of several very curious electrical experiments. One of the most interesting of these demonstrates the progressive motion of the electrical discharge. When he passes the shock through many small cannon balls, sometimes to the number of forty, placed upon small drinking goblets close by one another, all the sparks are seen and all the cracklings are heard at the same moment; but when he substitutes eggs (preferably ten or twelve) for the balls, the progress of the explosion is visible, every two giving a flash and a report separately.

He remarks that upon one occasion, as he re-entered a room which he had just before left, after making therein a number of experiments, he observed a small flame following him as he walked about swiftly while holding a lighted candle in his hand. The flame vanished whenever he stopped to examine it, and he attributed its appearance to the presence of sulphur thrown into the air by continued violent electrification.

References.—Hartmann, “Abhandlung von der verwandschaft,” etc., Hanover, 1759, pp. 58, etc., and 135; also his “Electrische experimente,” etc., Hanover, 1766, and his “Anmerkungen,” etc., 1764, 4to, p. 38; Friedrich Saxtorph, “Elektricitätsläre,” Vol. II; Hamburgisches Magazin (also Neues Hamb. Mag.) for 1759, Vol. XXIV, and for 1761, Vol. XXV; “Nov. Acta Acad. Nat. Curios,” Vol. IV. ss. 76–82, 126; “Göttingischen gemein. Abhand.,” von Jahr 1775.

A.D. 1759.—Wesley (John), the founder of Methodism (1703–1791) and the most eminent member of a very distinguished English family, publishes “The Desideratum; or Electricity made Plain and Useful, by a Lover of Mankind and of Common-sense.” In this, he relates at great length the cures of numerous physical and moral ailments, attributed to the employment of the electric fluid, under such curious headings as “Electricity, the Soul of the Universe,” “Electricity, the Greatest of all Remedies,” etc. (“The Library of Literary Criticism,” C. W. Moulton, Buffalo, 1901–1902, Vol. IV. pp. 110–129).

A.D. 1759.—Æpinus (Franz Maria Ulrich Theodor) (1724–1802), celebrated German natural philosopher, member of the Scientific Academies of Berlin and St. Petersburg, publishes in the latter city his most important work, “Tentamen Theoriæ Electricitatis et Magnetismi,” wherein he adopts, as did Wilcke, all the general principles of Franklin’s theory of positive and negative electricities. Therein he also shows that the phenomena of electricity depend mainly upon the tendency of the fluid to attain a state of equilibrium by passing from bodies containing an excess to others which have less than the natural quantity; that the electric fluid existing in the pores of all bodies moves without obstruction in non-electrics and with much difficulty in electrics; that all bodies contain a fluid whose particles mutually repel one another with forces decreasing as the distance between them increases, and, according to the same law, attract the particles of the bodies with which they are in combination.

It has already been shown that, in conjunction with Wilcke, he found the means of charging a plate of air. This experiment, suggested by some of the observations made by Canton and Franklin, led to what may be considered one of the greatest discoveries in the science of electricity, for in this was first demonstrated the grand principle of induction (see Grey at A.D. 1720), and the result led to Volta’s discovery of the electrophorus. Volta, also, was the first to apply to an electrometer the apparatus invented by Æpinus for condensing electricity.

Æpinus first discovers to its fullest the affinity existing between electricity and magnetism, explaining nearly all the phenomena of magnetism (“De Similitudine vis electricæ et magneticæ”; “Similitudinis effectuum vis magnet. et. elect.: novum specimen” in the “Novi Comment. Acad. Petrop.,” Vol. X. p. 296). He improves upon the methods employed by both Duhamel and Michell for the construction of artificial magnets in a different line from that employed by John Canton, A.D. 1753. He lays the bar to be magnetized upon the ends of the opposite poles of two powerful field magnets, and places two bunches of magnetic bars upon the middle of the bar, separating the bunches by a piece of wood and keeping together the poles of each of the same name as that of the powerful fixed magnet nearest to it. These two bunches are then held at an inclination of 15 to 20 degrees, and are drawn away from each other to the end of the bar which is to be magnetized, so that each half of the bar receives the same number of strokes. When the bar is very thick, the process should be repeated upon its reverse, and in order to make the result more effective, the united ends of the bars should at the outset be ground together, and pressure should be applied while the operation is going on.

Æpinus was the first to discover the polarity of the tourmaline. After M. Lechman acquainted him with its attractive power, he made many experiments, of which he communicated the very important results, during the year 1756, to the Academy of Sciences and Belles-Lettres at Berlin. Up to this time but little was known regarding the necessity of heat to excite the tourmaline. Æpinus found that he could electrify it to a high degree by placing the stone in boiling water, and that it was necessary to heat it to between 99½ degrees and 212 degrees Fahrenheit to develop its attractive powers. One of the extremities of the tourmaline terminated by the six-sided pyramid then becomes charged with positive electricity, while the other extremity is negative. When the stone is of considerable size, flashes of light can be seen along its surface.

M. De Romé Delisle, in his “Essai de Cristallographie,” Paris, 1772, p. 268, alludes to what has already been stated relative to the necessity of heating the tourmaline (see J. G. S. at A.D. 1707, and Leméry at A.D. 1717), and he gives an extract from the work attributed to Adanson, as mentioned at A.D. 1751. Delisle’s references embrace: “Act. Paris,” 1717, p. 9; “Act. Berolin,” 1756, p. 105; “Lettre du Duc de Noya Caraffa à M. de Buffon,” Paris, 1759; Ascendrecker, Aschentrecher, Aschenzicher (tire-cendre), “Trip: Tourmaline, Vog. min.” 191; “Act. Holmens,” 1768, p. 7; besides, at pp. 209, 233 and 245 he speaks of the electrical and phosphorescent properties of crystals, showing that the lapis lyncurius of the ancients is the hyacinth or zircon of to-day (see B.C. 321), and not, as many believe, either amber or belemnite (pierre de foudre, lapis fulminaris), while the hyacinth of old was a purple stone which, if now found, would be classed among the amethysts.

References.—“Allgemeine Deutsche Biographie,” Leipzig, 1875, Vol. I. p. 129; Æpinus, “Sermo Acad. de similitudine,” etc., 1758, and his “Recueil ... sur la tourmaline,” 1762; “Novi. Com. Petropol.,” for 1761, 1764, 1768; “Acta Acad. Moguntinæ,” Vol. II. p. 255; Leithead, “Electricity,” p. 289; Phil. Trans., Vol. LI. p. 394, and Vol. LVII. part i. p. 315; “Encycl. Brit.,” articles “Electricity” and “Magnetism”; Bigeon’s report in the “Annales de Ch. et de Phys.,” 2^e série, Tome XXXVIII. p. 150; Van Swinden, “Recueil,” etc., La Haye, 1784, Vols. I and II passim; Becquerel in Annales de Chimie et de Physique, Vol. XXXVI. p. 50; Thomson, “Hist. Roy. Soc.,” 1812, p. 184; “The Electrical Researches of the Hon. Henry Cavendish,” Cambridge, 1879, Nos. 1, 134, 340 and 549; Lord Kelvin (Sir Wm. Thomson), “Æpinus atomized,” in Phil. Mag. for March 1902, p. 257, etc., and in Journal de Physique for Sept. 1902, p. 605.

A.D. 1759.—Symmer (Robert) assails the theory announced by Dufay (see Franklin, A.D. 1752), and shows, in a paper submitted to the Royal Society, December 20, 1759, that all the electrical phenomena are produced by two distinct but coexistent fluids not independent of, but counteracting each other. He says that equal quantities of these fluids are contained in all bodies while in their natural condition; that when a body is positively electrified it does not hold a larger share of electric matter, but a larger portion of one of the active powers, and when negatively electrified a larger portion of the other, and not, as Franklin’s theory supposes, an actual deficiency of electric matter. Symmer’s theory is perhaps best explained in his own words, as follows: “It is my opinion that there are two electric fluids (or emanations of two distinct electric powers), essentially different from each other; that electricity does not consist in the efflux and afflux of these fluids, but in the accumulation of the one or the other in the body electrified; or, in other words, it consists in the possession of a larger portion of the one or of the other power than is requisite to maintain an even balance within the body, and lastly, that according as the one or the other power prevails, the body is electrified in one or the other manner.”

Very curious reading may be had by reference to the volumes of the Philosophical Transactions named below, in which Symmer details many experiments with pieces of silk, as well as with white and coloured, new and newly cleansed silk and worsted stockings. Therein he shows his ability to charge the Leyden jar with either positive or negative electricity, according as he presents a black or white stocking to the wire of the phial. These experiments, which Symmer admits to have made for the express purpose of proving the existence of two electricities, further illustrate the phenomenon of electrical cohesion, although the latter is still better demonstrated by means of panes of ordinary glass. He thus expresses himself: “Upon these considerations, we may expect, from the experiment in hand, the means of determining whether the distinction of electricity into two different kinds is merely nominal, or if there is an essential difference between them; for, after the glass plates have been electrified in one position, so as to be incapable of receiving any more electricity, if they be inverted, and in that new position presented to the chain and wire, and the globe again be put in motion, according as one or other of those opinions hold, corresponding effects will follow.”

Symmer also proves his two distinct powers of electricity by the experiment of passing the electric shock through a quire of paper instead of through a single card (“Lib. Useful Knowledge,” London, 1829, “Electricity,” p. 44).

References.—“Electricity in the Service of Man,” R. Wormell, London, 1900, p. xiv; Philosophical Transactions, Vol. LI. part i. pp. 171, 340, 366, 373, etc., 389, and Vol. LVII. p. 458; also Hutton’s abridgments, Vol. XI. p. 405; Nollet, “Lettres,” etc., Vol. III. p. 42; “Encycl. Brit.,” article “Electricity”; “Library of Useful Knowledge,” London, 1829, “Electricity,” Nos. 160 and 161.

A.D. 1760.—Mayer (Johann Tobias, Sen.) (1723–1762), one of the most celebrated German astronomers, director of the observatory at Göttingen, is the first to make known the law of the inverse square resulting from actual experimental investigation. This he does in a paper, “Inclination and Declination of the Magnetic Needle, as deduced from theory,” read before the Royal Society at Göttingen, wherein he states that the intensities of the magnetic attractions and repulsions vary inversely as the squares of the distances from the pole of a magnet. Consult “Magnetism,” in the ninth edition of the “Encyclopædia Britannica,” for additional reference to the above paper, also section 14 of the same work for an account of Mayer’s dipping needle as constructed by General Sabine.

References.—Delambre’s notice of the life of J. T. Mayer in the “Biographie Universelle”; Hutton’s “Mathem. Dict.”; Montucla, “Histoire des Mathématiques”; list of his works added to the éloge pronounced by Kaestner, Göttingen, 1762; “Abhandlungen von Galvani und andern,” Prague, 1793; Whewell, “History of the Inductive Sciences,” 1859, Vol. II. pp. 206, 221; Coulomb, “Mémoires Acad. Paris” for 1786 and 1787; “Royal Soc. Cat. of Sc. Papers,” Vol. IV. pp. 311–314; Lambert, “Reports of the Berlin Academy” for 1776.

Mayer (Johann Tobias, Jr.), 1752–1830, is the author of Memoirs on the magnetic needle as well as upon many electrical experiments, of which details may be found in the Journal der Physik of Friedrich A. C. Gren and in the “Comment Soc. Göttingen recent.”

A.D. 1760.—Delaval (E. H.) communicates between 1760 and 1764 several papers to the London Royal Society in reference to experiments made for the purpose of ascertaining the conducting powers of a body in different states. Therein, he shows that animal and vegetable substances lose their conducting powers when reduced to ashes, and that while metals are the best conductors, their oxides are non-conductors. His experiments made with island (Iceland) crystal (well known for its extraordinary property of double refraction), proved that it is affected by heat differently from other substances named, since the temperature necessary to render them electric makes the crystal non-electric. He had a piece of crystal of which, he said, one part became non-electric when greatly heated, while the other part, with the same or even a much greater heat, remained perfectly electric. These experiments did not, however, succeed with Sir Torbern Bergman, who repeated them with great care and who found that island crystal was a conductor in all cases, to whatever degree of heat it was exposed.

References.—Phil. Trans., Vol. LI. part i. p. 83; Vol LII. part i. pp. 353, etc., and part ii. p. 459; also Vol. LIII. part i. pp. 84–98; and Hutton’s abridgments, Vol. XI. pp. 334, 589; Vol. XII. p. 140; Thomas Thomson, “Hist. of Roy. Soc.,” p. 443; Thos. Young, “Course of Lectures,” 1807, Vol. II. p. 679, for notes on Dr. Wm. H. Wollaston’s paper concerning the double refraction of Iceland crystal.

A.D. 1760–1762.—Bergman—Bergmann—(Torbern Olof), celebrated Swedish astronomer, naturalist and chemist, writes several letters to Mr. Wilson, which are read before the Royal Society, Nov. 20, 1760, and March 18, 1762, wherein he alludes to the possibility of electrifying plates of ice in the same manner as plates of glass. In a subsequent letter he details experiments with silk ribbons of different colours, almost as curious as those of which an account has already been given (by Symmer at A.D. 1759), and from which he concludes that there is a certain fixed order regarding positive and negative electricity in which all bodies may be placed while other circumstances remain unchanged.

References.—Bergman’s “Bemerkung ... Isländischen Krystales,” “Comment ... electrica turmalini,” “Elektrische Versuche,” etc., and his other works referred to in the Philosophical Transactions, Vol. LI. p. 907; Vol. LIII. p. 97; Vol. LIV. p. 84; Vol. LVI. p. 236; also Hutton’s abridgments, Vol. XI. pp. 506, 705; Vol. XII. pp. 109, 343; “Nova Acta Soc. Upsal.,” “K. Schwedischen Akad. Abhand.,” “Aus dem Schwed. Magazine,” Phil. Mag., IX. p. 193; “Eng. Cycl.,” Vol. I. pp. 664–665; Gmelin’s “Chemistry,” Vol. I. p. 320; Thomas Thomson, “Hist. of the Royal Society,” London, 1812, pp. 444, 475–477.

A.D. 1761.—The many experiments made at this period by Ebenezer Kinnersley, of Philadelphia, relative to the two contrary electricities of glass and sulphur, are endorsed by his close friend Benjamin Franklin in his Letters at pp. 99, 100 and 102–105. He makes several curious observations on the elongation and fusion of fine iron wires whenever a strong charge is passed through them while in a state of tension, to which Dr. Watson makes special reference in a paper read before the Royal Society. He believes that lightning does not melt metal by a cold fusion, as Dr. Franklin and himself had formerly supposed, and that when it passes, for instance, through the blade of a sword, if the quantity is not very great, it may heat the point so as to melt it, while the broadest and the thickest part may not be sensibly warmer than before.

To ascertain the effects of electricity upon air, Kinnersley devised an instrument which he called an electrical air thermometer, and which is described at p. 626, Vol. VIII of the 1855 “Encyclopædia Britannica.” With this he could show the sudden rarefaction which air undergoes during the passage of the electric spark through it, heat being produced without accompaniment of any chemical change in the heated body.

Some other important observations made by Kinnersley, who, besides being an intimate friend, was the original associate of Ben. Franklin, are summed up as follows: A coated flask containing boiling water cannot be charged, the electricity passing off with the steam; but when the water gets cold the flask may be charged as usual. A person in a negative state of electricity standing upon an electric, and holding up a long sharp needle out of doors in the dark, observes light upon the point of it. No heat is produced by electrifying a thermometer, nor by passing shocks through large wire, but small wire is heated red-hot, expanded and melted (Phil. Trans. for 1763, Vol. LIII. p. 84; Thomson, “Hist. Roy. Soc.,” p. 445).

In the New York “Electrical Review” of May 13, 1905, will be found the following curious reference to the Boston Art Club exhibits of President R. H. W. Dwight:

“Among these is an interesting broadside, which gives a summary of two lectures on electricity by Ebenezer Kinnersley delivered in Faneuil Hall in September, 1751—the first lectures probably ever delivered on the then new subject of electricity. Kinnersley was an Englishman, who was head master in English literature in the College of Philadelphia, from 1753 to 1773, a student of science, who made a number of discoveries in electricity and invented a number of quaint electrical devices. He and Franklin were on intimate terms, and were closely associated in their electrical experiments. Kinnersley has been erroneously cited as an anticipator of Oersted’s discovery of the deflection of a magnetic needle by an electric current. The former’s experiment, however, was purely electrostatic. In the summary of these two lectures, among other things, it states that electricity ‘is an extremely subtile fluid; that it doth not take up any perceptible time in passing through large portions of space; that it is mixed with the substance of all other fluids and solids of our globe; that our bodies at all times contain enough of it to set a house on fire.’”

The exhibits of President Dwight are:

“An artificial spider animated by the electric fire so as to act like a live one; a shower of sand which rises again as fast as it falls; a leaf of the most mighty of metals suspended in the air, as is said of Mahomet’s tomb; electrified money which scarce anybody will take when offered to them; a curious machine, acting by means of the electric fire, and playing a variety of tunes on eight musical bells.”

This broadside of 1751 appears to antedate any other similar notice of electrical experiments.

The “Electrical Review” of April 23, 1904, p. 621, had published copy of an advertisement from the Massachusetts Gazette of March 7, 1765, giving notice of a course of lectures by David Mason, illustrated by “entertaining experiments on electricity similar to those cited in the broadside under date of 1751.” The advertisement of 1765, here referred to, appears at A.D. 1771.

References.—Sturgeon’s “Lectures,” London, 1842, p. 169; “The Electrical Researches of Hon. Henry Cavendish,” 1879, Nos. 125, 137, 213; Phil. Trans., Vol. LIII. part i. pp. 84–87; Vol. LIV. p. 208; Vol. LXIII, 1773, part i. p. 38; also the Hutton abridgments, Vol. XI. p. 702, and Vol. XIII. p. 370; Bertholon, “Elec. du Corps Humain,” 1786, Vol. I. pp. 23, 33, 214, 217, 220.

A.D. 1762.—Sulzer (Johann Georg), a Swiss philosopher, member of the Berlin Academy of Sciences, in his “Theory of Agreeable and Disagreeable Sensations” (“Theorie d. angenehmen u. unangenehmen Empfindungen,” Berlin, 1762), thus expresses himself: “When two pieces of metal, one of lead and the other of silver, are so joined together that their edges make one surface, a certain sensation will be produced on applying it to the tongue, which comes near to the taste of martial vitriol (vitriol of iron); whereas each piece by itself betrays not the slightest trace of that taste” (F. C. Bakewell, “Manual of Electricity” London, 1857, Chap. III. p. 28).

The passage in the edition “Nouvelle Théorie des Plaisirs,” published in 1767, is thus given by Sabine, “Electric Telegraph,” 1872, p. 15: “On taking two pieces of different metals—silver and zinc—and placing one of them above and the other underneath his tongue, he found that, so long as the metals did not make contact with each other, he felt nothing; but that when the edges were brought together over the tip of his tongue, the moment contact took place and during the time it lasted, he experienced an itching sensation and a taste resembling that of sulphate of iron....” Sulzer does not appear to have been much surprised at the result, thinking it “not improbable that, by the combination of the two metals, a solution of either of them may have taken place, in consequence of which the dissolved particles penetrate into the tongue; or we may conjecture that the combination of these metals occasions a trembling motion in the respective particles, which, exciting the nerves of the tongue, causes that peculiar sensation.”

And thus, remarks Pepper, a prominent fact has slept in obscurity from the time of Sulzer to the time of Galvani.

References.—Izarn, “Manuel,” Paris, 1804, p. 4; Sturgeon, Annals, Vol. VIII. p. 363; also note at p. 491 of Ronalds’ “Catalogue”; Mém. de l’Acad. de Berlin, “Théorie Générale du Plaisir”; also “Temple du Bonheur,” published at Bouillon (Pays Bas), 1769, Tome III. p. 124, this last-named work being alluded to in the Journal des Débats, 7 Vendémiaire, au X; Edm. Hoppe, “Geschichte,” 1884, p. 128; C. H. Wilkinson, “Elements of Galvanism,” Vol. I. p. 69, note; Albert’s “Amer. Ann. d. Artz,” Vol. II. Bremen, 1802.

A.D. 1762.—Ledru Comus, French Professor of Natural Philosophy, invents a mode of telegraphing which is described and fully illustrated in Vol. I of Guyot’s “Nouvelles Récréations Physiques et Mathématiques,” Paris, 1769; as well as at p. 278 of “Mémoires, Correspondance et Ouvrages Inédits de Diderot,” Paris, 1821, in one of the letters to Mlle. Voland dated July 28, 1762.

His apparatus consisted of two dials, each bearing upon it twenty-five letters of the alphabet, which were moved by the agency of magnets and of magnetized needles; but Auguste Guérout considers the contrivance to have been merely a speculative one, as will be seen by his article, reproduced from “La Lumière Electrique” of March 3, 1883, in No. 384 of the “Scientific American Supplement.”

References.—Journal de Physique for 1775, Vols. V and VI; for 1776, Vol. VII; and for 1778, Vol. I; “Scelta di Opuscoli,” Milano, 1776.

A.D. 1765.—Cigna (Giovanni Francesco), native of Mondovi, Italy, and nephew to the electrician Beccaria (A.D. 1753), became secretary to the society of savants who gave birth to the Royal Academy of Sciences at Turin, and whose Memoirs contain his work, “De novis quibusdam experimentis electricis,” 1765.

At pp. 31–65 of the above Memoirs is given a full account of Cigna’s many curious observations made with silk ribbons placed in various positions, and in contact with different surfaces, instead of with the silk stockings employed by Symmer (A.D. 1759). He thus supplies the main defect of Dufay’s theory (A.D. 1733) by proving that the two opposite electricities are produced simultaneously. On p. 47 of the same work will be found a report of Cigna’s experiment with ice to ascertain whether electric substances contain more electric matter than other bodies.

References.—Vol. III. p. 168 of Nollet’s “Letters,” for an account of his observations upon the electric attraction and repulsion between conducting substances immersed in oil; as well as Chap. II. s. 3., vol. i. of Van Swinden’s “Receuil,” etc., published at La Haye, 1784. Should also be consulted: Cigna’s “Memoirs on Electricity and Magnetism” in the “Miscellanea ... Taurinensia,” and the several communications made by him to Priestley, Lagrange and others in 1775 concerning Volta’s electrophorus; likewise “Memorie istorische ... di Gianfrancesco Cigna de Antonmaria Vassalli Eandi,” Torino, 1821.

A.D. 1766–1776.—Lambert (Johann Heinrich), a profound German mathematician, native of Upper Alsace, publishes in Vol. XXII of the “Reports of the Berlin Academy” two beautiful Memoirs upon the “Laws of Magnetic Force” and upon the “Curvature of the Magnetic Current,” both of which, according to Dr. Robison, would have done credit to Newton himself.

In the first Memoir, says Harris, the author endeavours to determine two very important laws; one relating to the change of force as depending upon the obliquity of its application, the other as referred to the distance. In the second Memoir the curves of the magnetic current are investigated by the action of the directive or polar force of a magnet upon a small needle. Lambert concludes that the effect of each particle of the magnet on each particle of the needle, and reciprocally, is as the absolute force or magnetic intensity of the particles directly, and as the squares of the distances inversely.

Noad states (“Manual,” London, 1859, p. 580) that Lambert’s deductions were confirmed twenty years later by Coulomb, through the agency of his delicate torsion balance, and more recently (about the year 1817) by Prof. Hansteen, of Christiania.

Previous to the above-named date, in 1760, Lambert had published, both at Leipzig and at Augsburg, his “Photometria, sive de Mensura et Gradibus Luminis, Colorum et Umbræ,” the sequel to a tract printed two years before, wherein he indicates the mode of measuring the intensity of the light of various bodies. The celebrated mathematician and astronomer, Pierre Bouguer (1698–1758), who had published, in 1729, his “Essai d’Optique,” etc., which was greatly enlarged in his “Traité,” etc., brought out by La Caille in 1760, may be considered the founder of this branch of the science of optics, to which the name photometry has been given by English writers. The photometer designed by Sir Benjamin Thompson, Count Rumford (entered at A.D. 1802), has been described in Phil. Trans. for 1794, Vol. LXVII. His method is to cast two shadows of a given object near each other on the same surface, the lights being removed to such distances that the shadows appear equally dark.

References.—Sir John Leslie’s “Fifth Dissertation” in the eighth “Encycl. Brit.”; Count Rumford’s photometer illustrated at Plate XXVII. figs. 387, 388, vol. i. of Dr. Thomas Young’s “Course of Lectures,” London, 1807; also Vol. II. pp. 282 and 351 of the same work, concerning photometry generally; Dredge and others, “Electric Illumination,” etc. (chiefly compiled from London Engineering), Vol. II. pp. 101–117; Brewster’s “Edin. Jour. of Sc.,” 1826, Vol. II. p. 321; Vol. III. p. 104; Vol. V. p. 139, for William Ritchie’s articles on the photometer of Mr. Leslie, and relative to an improved instrument upon the principles of Bouguer (Edin. Transactions, Vol. X. part. ii.); Lambert’s biography and the article “Magnetism” in the “Encycl. Brit.”; Harris, “Rudim. Magn.,” Part III. pp. 20, 33, 191–203.

It may be added that all the valuable manuscripts left by Lambert were purchased by the Berlin Academy, and were afterward published by John Bernoulli, a grandson of the celebrated John Bernoulli alluded to at A.D. 1700.

A.D. 1766.—Lullin (Amadeus), in his “Dissertatio physica de electricitate,” Geneva, 1766, at p. 26, alludes to Beccaria’s experiments, saying that he produced much greater effects with the electric spark by passing the latter through oil instead of water: oil being a much worse conductor, the spark in it is larger. At p. 38 of the same work he details the experiments made to prove the correctness of Mollet’s doctrine regarding the constant motion of electrical atmospheres, and at p. 42 are given his experiments to show the production of electricity in the clouds. With a long insulated pole projecting from the mountain side he observed, among other effects, that when small clouds of vapour produced by the sun’s heat touched only the end of the pole the latter was electrified, but that it was not affected if the entire pole was covered by the vapour (“Lib. Useful Knowledge,” “Electricity,” Chap. XI. Nos. 154, etc.).

Lullin, it is said, proposed a modification of Reusser’s plan of telegraphing, in manner stated at p. 69 of Reid’s 1887 “Telegraph in America.”

A.D. 1766.—L’Abbé Poncelet, a native of Verdun, France, publishes at Paris “La Nature dans la formation du Tonnerre,” etc., wherein he indicates a method of protecting from lightning residences, pavilions and other structures, by constructing them of resinous woods and lining them with either silk or waxed cloths. He quaintly remarks that as they thus present “on all sides resinous surfaces, which never receive phlogiston by communication, the latter (thunder and lightning), after having leaped lightly around the pavilion and finding itself unable to attack it, will probably depart in order to pursue its ravages elsewhere.”

References.—Scientific American Supplement, No. 66, p. 1053, for a copy of the frontispiece of the above-named work; also Figuier, “Exposition et Histoire,” etc., 1857, Vol. IV. pp. 234, 235.

A.D. 1767.—Bozolus (Joseph), an Italian Jesuit, Professor of Natural Philosophy at Rome, is the first (and not Cavallo, A.D. 1775) to suggest employing the active principle of the Leyden jar for the transmission of intelligence.

His plan is to place underground two wires which are to be brought at each station close enough to admit of the passage of a spark. One of the wires is to be connected with the inner coating and the other with the outer surface of a Leyden phial; the sparks observed at the opening between the wires being there made to express any meaning according to a preconcerted code of signals.

References.—Latin poem entitled “Mariani Parthenii Electricorum,” in six books, Roma, 1767, lib. i. p. 34 (describing the telegrafo elettrico scintillante); also Saturday Review, August 21, 1858, p. 190, and Cornhill Magazine for 1860, Vol. II. p. 66.

A.D. 1767.—Priestley (Joseph), the earliest historian of electrical science, publishes, by advice of Benjamin Franklin, the first edition of his great work, “The History and Present State of Electricity,” of which there were four other separate enlarged issues, in 1769, 1775, 1775 and 1794. During the year 1766 he had been given the degree of Doctor of Laws by the Edinburgh University and he had also, at the instance of Franklin, Watson and others, been made a member of the English Royal Society, which, a few years later, bestowed upon him the Copley medal.

Speaking of the above-named work, Dr. Lardner says (“Lectures, 1859, Vol. I. p. 136): “This philosopher did not contribute materially to the advancement of the science by the development of any new facts; but in his ‘History of Electricity’ he collected and arranged much useful information respecting the progress of the science.” Nevertheless, to him is due the first employment of the conductor supported by an insulating pillar, as described by Noad, who gives an account of Priestley’s electrical machine at Chap. IV of his “Manual”; and he is also the first to investigate upon an extensive scale the chemical effects of ordinary electricity. The observations of M. Warltire, a lecturer on natural philosophy, and Priestley’s own experiments in this line, made by passing the electric spark through water tinged blue by litmus, also through olive oil, turpentine, etc., as well as his researches more particularly upon the gases and upon the influence of the electric fluid in expanding solid bodies, are detailed at the “Electricity” chapter of the “Encycl. Brit.”

At pp. 660–665 of the fourth edition of his “History,” Priestley describes the experiments he made to illustrate what he called the lateral force of electrical explosions; that is, the tendency of the fluid to diverge, as is the case with lightning when any material obstruction lies in its path.

Perhaps the most important of all Dr. Priestley’s electrical discoveries (Thomson, “Hist. Roy. Soc.,” p. 445) was that charcoal is a conductor of electricity, and so good a conductor that it vies even with the metals themselves. When the conducting power of charcoal was tried by succeeding electricians, it was found to vary in the most unaccountable manner, sometimes scarcely conducting at all, sometimes imperfectly and sometimes remarkably well; a diversity naturally indicating some difference in the nature of the different specimens of English charcoal (Priestley’s “History,” etc., Part VIII. s. 3). Charcoal being examined by Mr. Kinnersley (at A.D. 1761), was also by him observed to vary in its conducting power. Oak, beech and maple charcoal he found to conduct satisfactorily; the charcoal from the pine would not conduct at all, while a line drawn upon paper by a heavy black lead pencil conducted pretty well (Phil. Trans., 1773, Vol. LXIII. p. 38).

References.—Priestley’s letter to Dr. Franklin (Phil. Trans., Vol. LXII. p. 360) concerning William Henley’s new electrometer and experiments; likewise the Phil. Trans., Vol. LVIII. p. 68; Vol. LIX. pp. 57, 63; Vol. LX. p. 192; Vol. LXII. p. 359; and the abridgments by Hutton, Vol. XII. pp. 510, 600, 603; Vol. XIII. p. 36; “Trans. of the Amer. Phil. Soc.,” O. S., Vol. VI. part i. p. 190, containing proceedings of the Society on the death of Joseph Priestley; Wilkinson’s “Elements of Galvanism,” etc., London, 1804, Vol. II. pp. 74–80; Noad’s Lectures, No. 4, Knight’s edition, pp. 182, 183; “Library of Useful Knowledge,” London, 1829, Chap. “Electricity,” pp. 41 and 45; “Library of Literary Criticism,” C. W. Moulton, Buffalo, 1901–1902, Vol. IV. pp. 444–456; “Essays, Reviews and Addresses” by James Martineau, London, 1890, Vol. I. pp. 1–42; “Mém. de l’Institut” (Histoire), Tome VI. 1806, p. 29 for Elogium; “Essays in Historical Chemistry,” T. E. Thorpe, London, 1894, pp. 28, 110; “Science and Education,” by Thos. Henry Huxley, New York, 1894, pp. 1–37; “Scientific Correspondence of Jos. Priestley,” by H. C. Bolton, New York, 1902; Dr. Thos. H. Huxley, “Science Culture,” 1882, p. 102; Warltire, in Muirhead’s translation of Arago’s “Eloge de James Watt,” pp. 99, 100; also the appendix to the last-named work, p. 157 and note.

A.D. 1767.—Lane (Thomas—Timothy), a medical practitioner of London, introduces his discharging electrometer, which is now to be found described and illustrated in nearly all works on electricity.

It consists of a bent glass arm, one end of which is attached to a socket in the wire of the Leyden jar, while the other end holds a horizontal sliding brass rod, or spring tube, which bears a ball at each extremity. The rod is usually divided into inches and tenths, indicating the force of the discharge which takes place when the knob of the jar is placed in contact with the prime conductor of an electrical machine, and the charge is strong enough to leap from one to the other. In Mr. Lane’s experiments the shocks were twice as frequent when the interval between the balls was one twenty-fourth of an inch as when twice as much: from which he concluded that the quantity of electricity required for a discharge is in exact proportion to the distance between the surfaces of the balls.

A combination of the Lane and other electrometers was made by Mr. Cuthbertson, as shown at p. 528, Vol. II of Nicholson’s Journal of Natural Philosophy, and at p. 451, Vol. LVII of the Philosophical Transactions.

References.—Phil. Trans. for 1805; Hutton’s abridgments, Vol. XII; p. 475; Cavallo, “Elements ... Phil.” 1825, Vol. II. p 197; Harris, “Electricity,” p. 103; Monthly Magazine, December 1805, and Tilloch’s Philosophical Magazine, Vol. XXIII. p. 253.

The Hutton abridgments contain, at p. 308, Vol. XV, the description of a new electrometer by Abraham Brook.

A.D. 1768.—Ramsden (Jesse), a very capable English manufacturer of mechanical instruments, member of the Royal Society and of the Imperial Academy of St. Petersburg, is said to be the first to construct an electrical machine wherein a plate of glass is substituted for the glass globe of Newton and of Hauksbee and for the glass cylinder of Gordon (at A.D. 1675, 1705 and 1742). The same claim which has been made for Martin de Planta, Swiss natural philosopher, appears to have no foundation. (See note at p. 401 of Ronalds’ “Catalogue.”)

References.—Journal des Sçavans, November 1788, p. 744; Phil. Trans., 1783; “Chambers’ Encyclopædia,” 1868, Vol. III. p. 812; Mme. Le Breton, “Hist. et app. de l’Electricité,” Paris, 1884, pp. 61, 62.

A.D. 1768.—Molenier (Jacob), physician to the French King, Louis XV, writes “Essai sur le Mécanisme de l’Electricité” for the purpose of showing the utility of the application of the electric fluid in medical practice. At p. 60 he explains the effects and results when applications are made more particularly to the nerves, and at pp. 65–67 he gives certificates of many of the cures he has effected of gout, rheumatism, tumours, cancers, loss of blood, as well as of pains and aches of various descriptions.

References.—Jallabert (A.D. 1749); Lovett (A.D. 1756); Bertholon (A.D. 1780–1781); Mauduyt (A.D. 1781); Van Swinden, “Recueil,” etc., La Haye, 1784, Vol. II. pp. 122–129 for the experiments of Sauvages, De La Croix, Joseph Elder von Herbert, H. Boissier and others; Thomas Fowler, “Med. Soc. of London,” Vol. III; M. Tentzel, “Collection Académique,” Tome XI; the works of L’Abbé Sans, Paris, 1772–1778; M. de Cazèles Masar’s “Mémoires et Recueils,” published 1780–1788, and reproduced in Vols. II and III of the “Mémoires de Toulouse”; Jacques H. D. Petetin, “Actes de la Soc. de Lyon,” p. 230; M. Partington, Jour. de Phys., 1781, Vol. I; Dr. Andrew Duncan’s “Medical Cases,” Edinburgh, 1784, pp. 135, 191, 235, 320; C. A. Gerhard, “Mém. de Berlin,” 1772, p. 141; Jour. de Phys., 1783, Vol. II; J. B. Bohadsch, “Dissertatio,” etc., Prague, 1751; Phil. Trans. for 1752; Patrick Brydone, Phil. Trans. for 1757; Geo Wilkinson, of Sunderland, “An account of good effects,” etc., in Medical Facts, etc., 1792, Vol. III. p. 52; M. Carmoy, “Observ. sur l’El. Med.,” Dijon, 1784; M. Cosnier, M. Maloet, Jean Darcet, etc.; “Rapport,” etc., 1783; Le Comus, “Dissertatio,” etc., 1761; Le Comus, “Osservazioni,” etc., 1776 (Jour. de Phys., 1775, Vols. V and VI; 1776, Vol. VII; 1778, Vol. I; 1781, Vol. II); Ledru, “Sur le traitement,” etc., 1783; Le Dr. Boudet, “De l’Elec. en Médecine,” conférence faite à Vienne le 6 Octobre, 1883.

A.D. 1769.—Bancroft (Edward Nathaniel), a resident physician of Guiana, openly expresses the belief that the shock of the torpedo is of an electrical nature. He alludes (“Natural History of Guiana”) also to the gymnotus electricus, which, he says, gives much stronger strokes than the torpedo; the shocks received from the larger animals being almost invariably fatal.

The discharge of the gymnotus has been estimated to be equal to that of a battery of Leyden jars of three thousand five hundred square inches, fully charged. At a later date, the American physicians, Garden and Williamson, showed that as the fluid discharged by that fish affects the same parts that are affected by the electric fluid; as it excites sensations perfectly similar; as it kills and stuns animals in the same manner; as it is conveyed by the same bodies that carry the electric fluid and refuses to be conveyed by others that refuse to take the fluid, it must be the electric fluid itself, and the shock given by the eel must be the electric shock.