Chapter XXV: Part II: pp. 254–256, 279, for some of his other correspondence (2)

REFERENCES.--De Saussure’s “Dissertatio de Igne,” “Exposition
abrégée,” etc. (translated by Giuseppe Toaldo, in both his
“Della maniera,” etc., and “Dei conduttori,” etc., Venezia, 1772
and 1778), “Voyage dans les Alpes,” all published at Geneva,
1759, 1771, 1779, also the important 1786 Neuchatel edition of
the last-named work, more particularly at pp. 194, 197, 203,
205, 206, 211, 212, 216, 218, 219, 228, 252, 254 of Vol. II, and
at pp. 197, 257 of Vol. IV; likewise his Memoirs relative to the
electricity of the atmosphere, of vegetables, of microscopic
animals, etc., etc., alluded to in _Journal de Physique_ for
1773, 1784, 1788; in _Journal de Paris_ for 1784, 1785; in Vol.
I of Lazaro Spallanzani’s “Opuscoli di fisica,” etc., for 1776;
in Vol. III of the “Opuscoli Scelti di Milano,” and in the
_Philosophical Transactions_. See also Jean Senebier, “Mémoire
historique,” etc., Genève, 1801; Louis Cotte in his “Traité,”
etc., “Mémoires,” etc., “Observation,” etc., Paris, 1762, 1769,
1772; in the “Mémoires de Paris,” Année 1769, “Hist.,” p. 19;
Année 1772, “Hist.,” p. 16, and in the _Journal de Physique_ for
1783, Vol. XXIII; the experiments of MM. Becquerel and Brachet
in Becquerel’s “Traité d’El. et de Magn.,” Paris, 1836, Vol.
IV. p. 110; Theodor Ægidius von Heller, “Beobach d. Atmosphär.
Elektricität.” (F. A. C. Gren, “Neues Journal der Physik”
for 1797, Vol. IV); Faujas de St. Fond, “Description,” etc.,
Vol. II. p. 271, as per George Adams’ “Essay on Electricity,”
London, 1799, p. 419; Noad, “Manual,” etc., London, 1859, p.
16; Poggendorff, Vol. II. p. 755; Rozier, XXXI. pp. 317, 374;
XXXIV. p. 161; articles “Meteorology and Electricity” in the
“Encyclopædia Britannica”; Thomas Young, “Course of Lectures,”
etc., London, 1807, Vol. II. pp. 447, 466–471.

=A.D. 1784.=--Swinden (Jan Hendrik Van) (1746–1823), who had been made Professor in the University of Franequer at the early age of twenty (1767), and was at this time occupying the Chair of Natural Philosophy and Mathematics at Amsterdam, publishes in three volumes, at La Haye, his “Recueil de Mémoires sur l’Analogie de l’Electricité et du Magnétisme,” etc. (“De Analogia ...” in Vol. II of the “Neue Abhandl. der Baierischen Akad. Phil.”). The latter contains all the essays sent to the Electoral Academy of Bavaria on the subject--“Is There a Real and Physical Analogy Between Electric and Magnetic Forces; and, if Such Analogy Exist, in What Manner Do These Forces Act Upon the Animal Body?”

Van Swinden’s essay, which gained him one of the prizes, shows that, in his opinion, the similarity between electricity and magnetism amounts merely to an apparent resemblance, and does not constitute a real physical analogy. He infers from this that these two powers are essentially different and distinct from one another, but the contrary opinion was maintained by Profs. Steiglehuer and Hubner, who contended that so close an analogy as that exhibited by these two classes of phenomena indicated the effects of a single agent, varied only in consequence of a diversity of circumstances.

The eminent professor, Gerard Moll, of Utrecht, has communicated to the Edinburgh _Journal of Science_ (1826, Vol. I. part ii. pp. 197–208) a biographical notice of Van Swinden, wherein he gives a list of the latter’s principal works and there speaks of one of his best-known productions in following manner: “The _Positiones Physicæ_ (Opusc. Scelti, X. 7), as far as they are published (Harderovici, 1786, Vol. I and Vol. II. part i.), are allowed to rank among the best elements of natural philosophy, and have been found by actual experience to belong to the best sources from which the young student could draw his information on those parts of natural philosophy, and its general principles, as are contained in the first volume and part of the second, which is all that was published. The work itself is on a most extensive plan; and the multifarious avocations which crowded on Van Swinden in Amsterdam delayed the publications, and made him afterward abandon all thoughts of completing a work which would have done the greatest honour to its author, and which even now, unfinished as it is, is celebrated as an excellent specimen of sound reasoning and profound learning.”

Van Swinden was the first President of the Royal Institute of the Netherlands. He entered with ardour into all the new discoveries of his day and kept up an extensive correspondence with many of the leading scientific characters of the time, notably with the Swiss philosopher, Charles Bonnet (whose “Contemplations de la Nature” he annotated extensively); with Dr. Matthew Maty (who became secretary of the Royal Society upon the resignation of Dr. Birch in 1765, and who was appointed, by the king, principal librarian of the British Museum upon the death of Dr. Gowin Knight, 1772); with the eminent French physician, Michel-Augustin Thouret, Dean of the Paris “Faculté de Médecine”; as well as with Delambre, Euler, De Saussure, and many others who have been named elsewhere in this “Bibliographical History.”

The following is further extracted from Prof. Moll’s interesting paper: “Mr. Biot, in his treatise on Natural Philosophy (Tome III. p. 143) asserts that we are indebted to Cassini IV. (see Jean Dominique, Comte de Cassini, at A.D. 1782–1791) for much of what we know even about the diurnal variation of the needle. This, I think, is not fair. We do not mean to undervalue Mr. Cassini’s observations, but it is unquestionable that long before the publication of that philosopher’s work, Mr. Van Swinden had observed and published (‘Recherches sur les aiguilles aimantées et leurs variations’--Mémoires présentés à l’Académie des Sciences de Paris, Tome VIII--prize essay 1777) that which Mr. Biot less accurately is pleased to ascribe to his countryman. In this respect, however, Mr. Van Swinden was treated with more justice by other eminent philosophers, such as Haüy, Halley and Burkhardt.” (Consult also the “Acta Acad. Petrop.” for 1780, Part I. Hist. p. 10.)

In the afore-named very meritorious work, “Recueil de Mémoires,” etc., crowned by the Bavarian Academy, Van Swinden has treated fully of the then current theories relative to electrical and magnetical phenomena, reviewing the entire field of their application. In so doing he has necessarily made numerous references to discoverers and experimenters of all countries, the names of many of which appear in the present compilation, and while it is, of course, useless here to quote these anew, it has been thought best, for a record, to specify such as are infrequently met with, and which appear in many of his most important articles, even at the risk of being accused of diffuseness or prolixity. They are as follows:

REFERENCES.--John T. Needham (Vol. IV, Mem. Brussels Acad. for
1783); _Phil. Trans._, 1746, p. 247; J. G. Lehmann (“Abhandlung
von Phosph.”; “Von Magnet Theilen im Sande,” “Novi Com. Acad.
Petrop.,” Vol. XII. p. 368, etc.); M. De La Cépède, “Essai sur
l’El. nat et artif.”; C. E. Gellert (“Com. Acad. Petrop.,” Vol.
XIII. p. 382, Exp. 15, 16); J. F. Henckel, “Pyritologia,” etc.;
J. E. Von Herbert, “Theor. Phæn. Elect.,” cap. 4, prop. 8; C.
F. M. Déchales, “Mundus Mathematicus,” lib. 1, _Quartus Exper.
Ordo._, exp. 16, Tome II. p. 488, ed. 2, etc.; M. Marcel’s
Dissertation on powdered magnets, which appears in the Dutch
“Uitgezogte Verhandelingen,” Vol. I. p. 261, etc.; Jean M. Cadet
(“Nova Acta. Physico. Med. Acad. Natur. Curios.,” Tome III);
Abbé Giraud-Soulavie (“Comment. ... Œuvres de Mr. Hamilton,”
note 4, p. 303); J. B. Le Roy (“Mém. de l’Acad. de Paris,”
for 1753, p. 447; for 1772, p. 499; _Jour. de Phys._, Vol.
II); Rudolph Richard (“Magazin d. Hamb.,” IV. p. 681); Gilles
A. Bazin, “Descrip. des Cour, Mag.,” Plates 14, 16–18; J. F.
Gross, “Elektrische Pausen,” Leipzig, 1776; _Jour. de Phys._,
Vol. X. p. 235; Niccolo Bammacaro, “Tentamen de vi Electrica,”
etc., s. 6; Samuel Colepress (_Phil. Trans._, 1667, No. 27,
Vol. I. p. 502); E. F. Du Tour, “Discours sur l’aimant,” s.
27; “Recueil des Prix de l’Acad. de Paris,” Tome V. mém. ii.
p. 49; “Mém. Math, et Phys.”; Mr. Calendrin, at Van Swinden’s,
Vol. I. pp. 233, etc.; M. Blondeau (“Mém. de l’Acad. de
Marine,” Brest., Tome I. s. 46, pp. 401–431, 438); J. A. Braun,
“Observations,” etc.; “Novi. Comment. Acad. Petrop.,” Vol. VII.
pp. 388, 407; M. Antheaulme (“Mém. sur les aimants artif.”
(prize essay), 1760; “Mém. de l’Acad. Roy.,” 1761, p. 211; Van
Swinden, 1784, Vol. II. pp. 95, 170); J. N. Reichenberger,
“Directorium magneticum magneticis,” etc., and “Hydrotica,” as
at Van Swinden, 1784, Vol. II. pp. 272–273; Geo. C. Schmidt,
“Beschr., einer Elektrisir Masch.,” etc., 1778; M. De la Folie
(_Jour, de Phys._, 1774, Vol. III. p. 9); Cölestin Steiglehner,
“Obs. phaenom. elect.,” “Ueber die Annal der Elek. und des
Magn.”; Lorenz Hubner, “Abh. u. d. Annal. u. mag. Kraft”; Jos.
Thad. Klinkosch, “Schreiben,” etc., “Beschreib. d. Volta ...
Elektrophors.” Reference should also be made to Noad, “Manual,”
etc., p. 641; Encycl. Brit., 1857, Vol. XIV. p. 6; “Messager des
Sciences et des Arts,” Gand, 1823, pp. 185–201, detailing all of
Van Swinden’s works; Antoine Thillaye’s treatise presented to
the Ecole de Médecine le 15 Floréal, An. XI; Butet (“Bull, des
Sc. de la Soc. Philom.,” No. 43, Vendémiaire, An. IX).

=A.D. 1784.=--Cotugno (Domenico), Professor of Anatomy at Naples, thus addresses Le Chevalier G. Vivenzio under date October 2, 1784: “The observation which I mentioned some days ago, when we were discoursing together of the electrical animals, upon which I said I believed the mouse to be one of that number, is the following: Toward the latter end of March, I was sitting with a table before me and observing something to move about my foot, which drew my attention. Looking toward the floor I saw a small domestic mouse, which, as its coat indicated, must have been very young. As the little animal could not move very quick, I easily laid hold of it by the skin of the back and turned it upside down; then with a small knife that laid by me, I intended to dissect it. When I first made the incision into the epigastric region, the mouse was situated between the thumb and finger of my left hand, and its tail was got between the last two fingers. I had hardly cut through part of the skin of that region, when the mouse vibrated its tail between the fingers, and was so violently agitated against the third finger that, to my great astonishment, I felt a shock through my left arm as far as the neck, attended with an internal tremor, a painful sensation in the muscles of the arm, and such giddiness of the head, that, being affrighted, I dropped the mouse. The stupor of the arm lasted upward of a quarter of an hour, nor could I afterwards think of the incident without emotion. I had no idea that such an animal was electrical; but in this I had the positive proof of experience.” (See G. Vivenzio, “Teoria e pratica della elettricità med.” ... Napoli, 1784.)

Cotugno’s observations attracted much attention throughout Italy and gave rise to many experiments, notably by Vassalli, who, however, merely concluded from them that the animal’s body could retain accumulated electricity in some unaccountable manner.

REFERENCES.--_Essai sur l’histoire_, etc., J. B. Biot, p. 9;
_Journal de Physique_, XLI. p. 57; _Mémoires Récréatifs_,
etc., par Robertson, Paris, 1840, Vol. I. p. 233; Cavallo,
_Electricity_, London, 1795, Vol. III. p. 6; Izarn, _Manuel_,
Paris, 1804, p. 4; _Journal Encyclopédique de Bologne_, 1786,
No. 8; Poggendorff, Vol. I. p. 417; Sue, aîné “Hist. du Galv.,”
Vol. I. pp. 1–2.

=A.D. 1785.=--Coulomb (Charles Augustin de), the founder of _electro-statics_ and of the school of experimental physics in France, invents the torsion balance, with which he discovers the true law of electric and magnetic attractions and repulsions. Some have asserted that Lord Stanhope had previously established the law with regard to electricity, but it has not been seriously questioned that its extension to magnetism belongs exclusively to Coulomb. Johann Lamont (“Handbuch ...” p. 427) gives the credit of the latter discovery to Giovannantonio Della Bella, of Padua, who is mentioned by Poggendorff (“Biog.-Liter. Handwörterbuch,” Vol. I. p. 139) as the author of several works on electricity and magnetism, but the claim does not appear to be established upon any satisfactory foundation.

With his torsion balance, or rather electrometer, Coulomb measured the force by the amount of twist it gave to a long silken thread carrying a horizontal needle, constructed, preferably, of a filament of gum-lac or of straw covered with sealing-wax. From his experiments he concluded: That the attractive force of two small globes, one electrified positively and the other negatively, is in the inverse ratio of the squares of the distances of their centres, and that the repulsive force of two small globes, charged either with positive or negative electricity, is inversely as the squares of the distances of the centres of the globes (“Mém. de l’Acad. Roy. des Sciences,” 1784, 1785).

In one of his three memoirs to the French Academy during 1785, he states that a balance used by him was so delicate that each degree of the circle of torsion expressed a force of only one hundred-thousandth of an English grain, that another, suspended by a single fibre of silk four inches long, made a complete revolution with a force of one seventy-thousandth of a grain, and turned to the extent of a right angle when a stick of sealing-wax, which had been rubbed, was presented to it at the distance of a yard. It is said that a similar electrometer has been constructed in which the movement of one degree recorded a force not exceeding twenty-one million six-hundred-thousandths of a grain.

The many valuable experiments made by Coulomb on the dissipation of electricity and upon the distribution of electricity upon the surfaces of bodies are fully recorded in the able article of Sir David Brewster in the “Encyclopædia Britannica” (F. C. Achard, “Mém. de Berlin,” 1780, p. 47); M. Vernier, “De la dist. ... conducteurs,” Paris, 1824; J. L. F. Bertrand, “Programme d’une thèse ...” Paris, 1839; D. Bourdonnay, “Sur la dist. ... conducteurs,” Paris, 1840; Ed. A. Roche in “Montp. Acad. Sect. Sciences,” Vol. II. p. 115).

He discovered that shellac is the most perfect of all insulators, also that a thread of gum-lac insulates ten times better than a dry silken thread of the same length and diameter: and he established the law that the densities of electricity insulated by different lengths of fine cylindrical fibres, such as those of gum-lac, hair, silk, etc., vary as the square root of the lengths of the fibre.

Besides the communications above alluded to, Coulomb sent to the French Academy, during the years 1786, 1787, 1788 and 1789, many papers upon Electricity and Magnetism, and, up to within two years of his death (1806), he made many notable experiments, especially in magnetism, of which full accounts are given in several of the Mémoires noted at foot. The theory of the two magnetic fluids appeared in his 1789 paper. It is also in this same paper that Coulomb describes his improved method of making artificial magnets by employing compound magnets as first made use of by Gowin Knight and as explained at A.D. 1746. Still further improvements in these were brought about more particularly by the young Flemish scientist, Etienne Jean Van Geuns (1767–1795), by Jean Baptiste Biot (see A.D. 1803), and by the Rev. Dr. Scoresby during the year 1836.

Coulomb found that a steel wire is, by twisting, rendered capable of being nine times more strongly magnetized; that the magnetic power dwells on the surface of iron bodies and is independent of their mass; that the directive force of a magnetized bar reached its maximum when tempered to a bright cherry-red heat at 900 degrees, and that every substance is susceptible of magnetism to a degree of actual measurement. This last important research was communicated by him to the French Institute during the year 1802. His experiments proved that a grain of iron could communicate sensible magnetism to twenty pounds’ weight of another substance, and that when even beeswax had incorporated with it a portion of iron filings equal only to the one hundred-and-thirty-thousandth part of its weight it was yet sensibly affected by the magnet.

According to Dr. Thomas Young, Coulomb’s improvements in the theory of electricity may be considered as having immediately prepared the way for the elegant inventions of Volta and for the still more marvellous discoveries of Davy. Dr. Young gives reports of some of Coulomb’s experiments at p. 439, Vol. II of his “Course of Lectures” London, 1807 (“Journal of the Royal Institution” Vol. I. p. 134; “Décade Philosophique,” No. 21).

REFERENCES.--“Mém. de l’Acad. Royale des Sciences,” Paris,
1784, p. 266; 1785, pp. 560, 569, 578, 612; 1786, p. 67; 1787,
p. 421; 1788, p. 617; 1789, p. 455; “Mém. de l’Institut,” Vol.
III. p. 176; Vol. IV. p. 565, and Vol. VI. for 1806; “Mém. de
Math. et de Phys.” Vols. VIII and IX; “Mémoires de Coulomb,”
Vol. I of the “Collection de Mémoires relatifs à la Physique,”
Paris, 1884; “Cat. of Sc. Papers Roy. Soc.,” Vol. III. p. 73;
“Abstracts of Papers of Roy. Soc.,” Vol. II. p. 402; “Bull.
de la Soc. Philom.,” Nos. 3, 31, 61, 63, and for 1795, 1802;
_Journal de Physique_, Vols. XLV (II), pp. 235, 448; LIV. pp.
240, 267, 454; LV. p. 450 (for Carradori’s report); Ch. N. A.
De Haldat du Lys (“Mém. de Nancy” for 1841); _Phil. Magazine_,
Vols. XI. p. 183; XII. p. 278; XIII. p. 401; XV. p. 186; Rozier,
XXVII. p. 116; XLIII. p. 247; Gilbert, XI. pp. 254, 367; XII.
p. 194; Dr. Young, “Course of Lectures,” London, 1807, Vol. I.
pp. 682, 685, 686; “Royal Society Cat. of Sc. Papers,” Vol.
II. p. 73; Eighth “Britannica,” Vol. XIV. pp. 37–38; Humboldt,
“Cosmos,” 1859, Vol. V. p. 61; Schaffner, “Manual,” 1859, p.
56; Biot’s article in the “Biographie Universelle” and Biot’s
“Traité de Physique,” Paris, 1816, Vols. II, III; Dr. Thomas
Thomson, “Outline of the Sciences,” etc., London, 1830, pp.
350, 351, 379–422; Harris, “Rudim. Magn.,” Parts I, II. p. 56.
See also description of the electrometer of Colardeau and the
electro-micrometer of Delaunay, in the latter’s “Manuel,” etc.,
Paris, 1809, pp. 66, 76–80, and Plate V. fig. 61, as well as
Libes’ “Dict. de Phys.,” Vol. I. p. 406.

=A.D. 1785.=--The Canon Gottoin de Coma, friend of Alessandro Volta, observes that an iron wire about thirty feet in length will give a sound under certain conditions of the atmosphere when stretched in the open air. The circumstances that accompany, as well as those that favour the production of the phenomenon, says Prescott, demonstrate that it must be attributed to the transmission of atmospheric electricity. This transmission does not occur in a continuous manner, like that of a current, but is observable by a series of discharges.

REFERENCES.--Knight’s _Mechanical Dictionary_, 1876, Vol. III.
p. 2515; Prescott’s “The Speaking Telephone,” etc., 1879, p.
122; _Encyl. Britannica_, 1860, Vol. XXI. p. 631.

=A.D. 1785.=--Marum (Martin Van), a Dutch electrician who had in 1776 taken the degree of M.D. at the Academy of Gröningen, constructs for the Teylerian Society at Haarlem, with the assistance of John Cuthbertson, an electrical machine said to be the most powerful theretofore made. According to Cavallo (_Nat. Phil._, 1825, Vol. II. p. 194) it consisted of two circular plates of French glass, each sixty-five inches in diameter, parallel with each other on a common axis, and about seven and a half inches apart. Each plate was excited by four rubbers, the prime conductor being divided into two branches which entered between the plates and, by means of points, collected the electric fluid from their inner surfaces only.

In Van Marum’s machine, the positive and negative electricity could only be obtained in succession, but Dr. Hare, of the University of Pennsylvania, remedied this by causing the plates to revolve horizontally. It is said the machine was so powerful that bodies at a distance of forty feet were sensibly affected; a single spark from it melted a leaf of gold and fired various kinds of combustibles; a thread became attracted at the distance of thirty-eight feet, and a pointed wire was tipped with a star of light at a distance of twenty-eight feet from the conductor.

Descriptions of his machines are given by Dr. Van Marum in letters to the Chevalier Marsiglio Landriani and to Dr. Ingen-housz, both printed in Haarlem during 1789 and 1791. The first quarto volume of _Nicholson’s Journal_ also contains a reference thereto and gives (p. 83) the extract from a letter read June 24, 1773 (_Phil. Trans._, Vol. LXIII. pp. 333–339), addressed to Dr. Franklin, F.R.S., by John Merwin Nooth, M.D., who describes improvements by which machines are rendered effective in all kinds of weather. Nooth was the inventor of the silk flap, of which mention was made in the description of Cavallo’s machine (under A.D. 1775).

Van Marum also constructed a powerful battery, the metallic coatings of which were equal to 225 square feet, enabling him to give polarity to steel bars nine inches long, nearly half an inch wide and one-twelfth of an inch thick, as well as to sever a piece of boxwood four inches diameter and four inches long, and to melt three hundred inches of iron wire one hundred-and-fiftieth of an inch in diameter, or ten inches of one-fortieth of an inch in diameter. It is said that, during these experiments, the report was so loud as to stun the ears, and the flash so bright as to dazzle the sight.

Dr. Van Marum likewise made experiments upon the electricity developed during the melting and cooling of resinous bodies, which are detailed in the article “Electricity” 8th Edit. “Encyclopædia Britannica,” Vol. VIII. p. 565, and also upon the effects of electricity on animals and vegetables, which are given at pp. 49–51 of the article “Electricity” in the “Library of Useful Knowledge,” as well as in the 1855 Edit. “Encyclopædia Britannica,” Vol. VIII. pp. 602, 603.

In 1785 again Van Marum discovered that electric sparks, on passing through oxygen gas, gave rise to a peculiar sulphurous or electrical odour, which Cavallo called “electrified air,” and the presence of which Dr. John Davy, brother of Sir Humphry Davy, found the means of detecting.

During the month of October 1801 Volta wrote a letter to Van Marum asking him to make, in concert with Prof. C. H. Pfaff, of Kiel, several experiments on the electricity of the pile with the very powerful apparatus of the Teylerian Society. The extended researches of these two scientists are embodied in the _Phil. Mag._, Vol. XII. p. 161, as well as in the “Lettre à Volta” etc., published at Haarlem during 1802, and are likewise treated of in a very complete manner throughout Chaps. XVI and XXXII of Wilkinson’s well-known work on galvanism. Their united observations confirm the doctrine of Volta as to the identity of the current of the fluid put in motion by the voltaic pile and that to which an impulsion is given by an electrical machine. Thus is answered the question asked during May 1801 by the Haarlem Society of Sciences, viz. “Can the voltaic pile be explained in a satisfactory manner by the known laws and properties of electricity; or is it necessary to conclude the existence of a particular fluid, distinct from the one which is denominated electrical?” They also demonstrated that the current put in motion by the voltaic pile has an enormous celerity “which surpasses all that the imagination can conceive.” With a pile of one hundred and ten pairs of very large copper and zinc plates, they made experiments on the fusion of iron wires and ascertained the causes of the more considerable effects of large piles in the fusion and oxidation of metals, proving, among other facts, as Biot and Cuvier had already done, that a part of the oxygen is absorbed whether the operation be carried on in the open air or _in vacuo_ (Biot and Cuvier, _Soc. Philomathique_, An. IX. p. 40; _Annales de Chimie_, Vol. XXXIX. p. 247).

Another of Van Marum’s experiments is related in a letter to M. Berthollet, wherein he says: “... I have succeeded in the decomposition of water, by means of the current of the electrical machine, provided with a plate of thirty-one inches diameter, constructed by me on a new plan (see the _Journal de Physique_ for June, 1795).... I took a thermometrical tube, of the kind employed in making the most sensitive thermometers of Crawford and Hunter, for which purpose I had procured several of these tubes some time before in London. Its diameter interiorly was not more than the one-hundredth part of an inch; and I introduced into it an iron wire of the diameter of about the three-hundredth part of an inch, to the depth of about twelve inches. I now closed the end of my thermometrical tube with sealing wax in such a way that the extremity of the iron wire should scarcely project, and I placed the tube itself, by means of a cork, within a larger tube containing water. The rest of the apparatus was arranged in the customary manner. By directing the powerful current of the above-mentioned machine to this apparatus, the copper ball belonging to which, placed on the thermometrical tube, was at the distance of about three or four lines from the conductor, I succeeded in decomposing the water with a promptitude nearly equal to that which results from a voltaic pile of a hundred pairs of metallic plates.” This method of decomposing water is a very tedious one, and is in fact the result of an interrupted explosion, while the process of Dr. Wollaston (alluded to at A.D. 1801) is tranquil and progressive.

REFERENCES.--“Biogr. Univ.,” Vol. XLII. p. 600; J. G. Heinze,
“Neue elekt. versuche ...” Oldenberg, 1777; Tries’ claim to
Van Marum’s machine in Rozier, XL. p. 116; Prieur’s extract in
_Annales de Chimie_, Vol. XXV. p. 312; “Verhand. Genootsch.
Rott.,” VI for 1781 and VIII for 1787; _Journal de Physique_,
XXXI, 1787; XXXIII, 1788 (Marum en Troostwyk); XXXIV, 1789;
XXXVIII, 1791; XL, 1792; “Journal du Galvanisme,” XI, Cahier,
p. 187; “Journal des Savants” for August 1905; “Revue
Scientifique,” Paris, April 8, 1905, pp. 428–429; _Nicholson’s
Journal_ for March 1799, Vol. II. p. 527; Harris, “Electricity,”
pp. 62, 90, 171; Cuthbertson, “Practical Electricity,” London,
1807, pp. 166, 172, 197, 225; Cavallo, “Electricity,” 4th ed.,
Vol. II. p. 273; “Lib. of Useful Knowledge,” “Electricity,” p.
45; Wilkinson, “Elements of Galvanism,” etc., London, 1804, Vol.
II. pp. 106–128, 384; “Teyler’s Tweede Genootschap”; Gilbert,
_Annalen_, I. pp. 239, 256; X. p. 121; Rozier, XXVII. pp.
148–155; XXXI. p. 343; XXXIV. p. 274; XXXVIII. pp. 109, 447; XL.
p. 270; “Opus. Scelti,” IX. p. 41; XIV. p. 210.

=A.D. 1785.=--Sigaud de la Fond, Professor at the Collège d’Harcourt in Paris, publishes in the latter city his “Précis historique et expérimental des phénomènes electriques,” wherein he states having, as far back as 1756, made use of a circular plate machine provided with cushions and similar in shape to that which many claim to have originated with Ingen-housz and with Ramsden. (See A.D. 1779 and A.D. 1768.)

Sigaud de la Fond is also the author of “Description d’un Cabinet de Physique” (1784), “Cours de Physique,” etc. (1786), “Examen.,” etc. (1803) and of several treatises on medical electricity.

REFERENCES.--“Journal de Physique,” Vol. II. 1773; Figuier,
“Exposition et Histoire,” Paris, 1857, pp. 50, 74–76, 178;
Poggendorff, Vol. II. p. 927.

=A.D. 1785.=--In the “Nachricht von einer neuen Elektrisirmaschine des Herrn Walkiers von Saint Amand,” the last named gives a description of the electrical machine presented by him in 1784 to the Belgian Academy of Sciences.

It is also described and outlined in Delaunay’s “Manuel” named below, but, although very powerful in its effects, cannot be made readily available in consequence of its huge dimensions. M. Caullet de Veaumorel suggested the feasibility of changing the cylinders from a horizontal to a vertical position.

REFERENCES.--“Lichtenberg’s Mag.,” Vol. III. 1 st. p. 118;
Delaunay, “Manuel,” etc., 1809, pp. 14–16.

=A.D. 1785.=--Adams (George), mathematical instrument maker to his Majesty, writes an enlarged edition of his “Essay on Electricity,” etc., which first appeared the year previous and wherein, as its full title indicates, he endeavours to explain the theory and practice of that science and the mode of applying it to medical purposes. He illustrates many experiments and gives an Essay on Magnetism, in the treatment of which latter he acknowledges the valuable aid of Dr. J. Lorimer.

The fifth and last edition of the “Essay,” which was issued by William Jones in 1799, four years after Adams’ death, contains a communication on the subject of Medical Electricity by John Birch, the author of “Della Forza dell’ Elettricita,” etc., Napoli, 1778.

At p. 86 of the 1799 “Essay,” etc., Adams relates that, while M. Loammi Baldwin (“Memoirs of Amer. Acad.,” Vol. I. p. 257) held the cord of his kite during the approach of a thunderstorm, he “observed himself to be surrounded by a rare medium of fire, which, as the cloud rose nearer the zenith, and the kite rose higher, continued to extend itself with some gentle faint flashes.” At pp. 137, 186 and 222, he alludes to “A. Brook’s Miscellaneous Experiments and Remarks on Electricity,” etc., as well as to the Rev. John Lyon’s “Experiments and Observations of Electricity,” and refers to the “Journal of Natural Philosophy” (Vol. II. p. 438) for Nicholson’s experiments on the _plus_ and _minus_ of electricity.

=A.D. 1785.=--La Méthérie (Jean Claude de), French physicist naturalist, becomes sole editor of the “Journal de Physique, de chimie et d’histoire naturelle,” and publishes in Paris his “Essai Analytique,” etc., wherein amongst other observations he asserts that the electric spark results from the combination of oxygen with hydrogen.

He considers that all bodies exist in an electrical or magnetical condition, that we are only a temporary aggregation of molecules of matter governed in different ways by nature’s laws, and that excitability is produced by galvanic action resulting from the superposition of nervous and muscular fibres.

He is also the author of very interesting treatises on animal electricity communicated to the _Journal de Physique_ (Vol. XLII. pp. 252, 255, 292), and of which an account is given in Sue’s “Histoire du Galvanisme,” Paris, 1802, Vol. I. pp. 64–68. The last-named work also gives, at p. 80, an account of the letter on “Galvanism” sent to M. De La Méthérie by M. Leopold Vacca-Berlinghieri (_Journal de Physique_, Vol. XLI. p. 314).

REFERENCES.--“Biographie Générale,” Vol. XXIX. p. 209; Rozier,
XLI. p. 437; Delaunay, “Manuel,” etc., 1809, p. 15, also
Delaunay’s letter in _Phil. Mag._, Vol. XXVII. p. 260; C. H.
Wilkinson, “Elements of Galvanism,” London, 1804, Vol. I. p.
62; Vol. II. p. 9; “Opus. Scelti,” XXI. p. 373; _Journal de
Physique et Chimie_ (of which La Méthérie remained editor up to
the time of his death, during 1817), Vols. LIII, LIV, Pluviose,
An. XI. p. 161; also p. 157 for letter sent him by Giuseppe
Izarn; _Ann. di Chim. di Brugnatelli_, Vol. XIX. p. 156; Aubert,
“Elektrometische Flasche,” Paris, 1789.

=A.D. 1785.=--According to Prof. Tyndall, George Cadogan Morgan sought to produce the electric spark in the interior of solid bodies. He inserted two wires into wood and caused the spark to pass between them; the wood was illuminated with blood-red light or with yellow light according as the depth at which the spark was produced proved greater or less. The spark shown within an ivory ball, an orange, an apple, or under the thumb, illuminates these bodies throughout. A lemon is especially suited to this experiment, flashing forth, at every spark, as a spheroid of very brilliant golden light, and a row of eggs is also brilliantly illuminated throughout, at the passage of every spark from a Leyden jar. Morgan likewise made several experiments to ascertain the influence of electricity on the animal functions. These are alluded to at p. 602, Vol. VIII of the 1855 “Britannica,” and at p. 49 of “Electricity” in the “Library of Useful Knowledge.”

This George Cadogan Morgan (1754–1798) was an English physician and also a Professor of Natural Philosophy at Hackney, in an establishment founded by his uncle, Dr. Price. His “Lectures on Electricity” appeared in Norwich during the year 1794. In the second volume he describes (pp. 225–236) “the form, noise, colours and devastation of the electric flash,” and treats (pp. 383–397) of the “relation of the electric fluid to vegetation,” alluding more particularly to the experiments of Maimbray, Nollet, Achard, Duvernier, Ingen-housz, Van Breda, Dr. Carmoy and the Abbé d’Ormoy. He likewise gives an account of the northern lights, as well as descriptions of Bennet’s movable doubler and electroscope, and of Lane’s electrometer.

REFERENCES.--Morgan’s biography in Larousse, “Dict. Universel,”
Tome XI. p. 562, and in “Biog. Générale,” Tome XXXVI. p. 570;
“Bibl. Britan.” An. VII. vol. ii. pp. 129, 223, and Vol. XII. p.
3.

=A.D. 1786.=--Rittenhouse (David), an American physicist and astronomer who afterward became F.R.S. and succeeded Dr. Franklin as President of the Am. Philos. Soc., publishes his theory of magnetism in a letter to John Page at Williamsburg, which is reproduced at folio 178 of Vol. II, old series, of the Transactions of the above-named Society.

“Were we called upon,” says Renwick, “to assign him a rank among the philosophers whom America has produced, we should place him, in point of scientific merit, as second to Franklin alone.”

REFERENCES.--“Trans. Am. Phil. Soc.,” Vol. II, O.S., pp. 173,
175, for Page and Rittenhouse, and Vol. III. for Rittenhouse and
Jones, as well as Rittenhouse and Hopkinson, upon “Meteors and
Lightning.”

=A.D. 1786.=--Galvani (Aloysio or Luigi), an Italian physician, who, at the age of twenty-five, was Professor of Anatomy at the University of Bologna, is led to the discovery of that important branch of electricity which bears his name. The manuscript giving the result of his experiments upon the Electricity of Metals is dated Sept. 20, 1786.

From papers in the “Bolognese Transactions” noted below, it would appear that he had, even before the year 1780, made many observations on the muscular contraction of frogs by electrical agency. Upon one occasion his wife happened to be holding a scalpel against the dissected legs and parts of the spine of a frog, which lay in close proximity to the conductor of an electrical machine recently charged by one of Galvani’s pupils. She noticed that whenever the dissecting knife touched the muscles they were violently convulsed, and, upon communicating the fact to her husband, he repeated and extended the experiment and found it necessary to pass the electric fluid through a metallic substance in order to develop the result originally observed. At first the frogs had been hung upon a copper hook fastened to an iron railing, but he afterward substituted an arc composed of both metals and with which he could readily produce the same results as were obtainable with an electrical machine.

Galvani also made experiments to ascertain the effect of atmospheric electricity upon the nerves of frogs. He connected the latter with rods leading to lightning conductors erected upon the roof of his house, attaching also ground wires to the legs of the animals, and found that the same convulsions appeared whenever lightning was seen and likewise when heavy storm clouds passed over the house.

The results of his many interesting observations were first made public in the celebrated work entitled “Aloysii Galvani de viribus electricitatis in motu musculari. Commentarius: cum Aldini dissertatione et notis,” which appeared during 1791–1792. Therein, he expresses the belief that the bodies of animals possess a peculiar kind of electricity by which motion is communicated through both nerve and muscle, positive electricity going to the nerve, while negative electricity goes to the muscle, and that the muscles represent the exterior and the nerves the interior of the Leyden jar, the discharge being similarly produced by the metal which communicates with both.

Galvani’s singular experiments naturally attracted everywhere the attention of philosophers, by whom they were repeated and varied, but by none were they more assiduously prosecuted than by Volta, who was then a Professor at the Pavia University, and who, as already indicated, was led by them to the discovery of the voltaic pile and of voltaic or galvanic electricity.

The announcement of Galvani’s observations was made in Germany, notably by J. F. Ackermann (“Medicinisch-chirurgische Zeitung”), by M. Er (“Physiologische Darstellung der Lebenskräfte”), by M. Smuck (“Beiträge zur weiteren Kenntniss,” etc.), and by F. A. C. Gren (“Journal der Physik,” Vols. VI, VII and VIII), while experiments were continued upon an extensive scale by the Italians F. Fontana, Carlo Francesco Bellingeri, M. Giulio and F. Rossi, as well as by Samuel T. Von Sömmering, by Wilhelm Behrends and by Karl Friedrich Kielmayer (Kielmaier), Professor of Medicine at the Tübingen University (Poggendorff, Vol. I. p. 1253). For the curious galvanic experiments of the celebrated French physician Larrey, and of Stark, Richerand, Dupuytren and Dumas, see “Bulletin des Sciences de la Société Philomathique,” 1793, Nos. 23, 24, and “Principes de Physiologie,” Vol. II. p. 312.

REFERENCES.--C. Alibert, “Eloges Historiques de Galvani,
Spallanzani, Roussel et Bichat ...” Paris and Bologna, 1802–1806
(“Mém. de la Soc. d’Emul. de Paris,” Vol. IV; S. Gherardi,
“Rapporto sui Manoscrotti,” Bologna, 1840, p. 19); Poggendorff,
Vol. I. p. 839; Thomas Thomson, “History of the Royal Society,”
London, 1812, pp. 450, etc.; Thomas Young, “Course of Lectures,”
London, 1807, Vol. II; “Bolognese Transactions” for papers
dated April 9, 1772, April 22, 1773 and Jan. 20, 1774; Sabine,
“El. Tel.,” 1872, pp. 16–18; Knight’s “Mech. Dict.,” Vol.
II. pp. 936, 937, for extract from report of Nat. Inst. of
France, July 4, 1798; “Johnson’s Encyclop.,” 1877, Vol. I. p.
1510; Bakewell’s “Electricity,” p. 26; “Encyclop. Britannica,”
1855, Vol. VIII. p. 530, and Vol. XXI. pp. 609, etc.; Fahie’s
“History,” etc., 1884, pp. 180–185; _Phil. Trans._, 1793;
Miller, “History Philos. Illustrated,” London, 1849, Vol. IV.
p. 333; Thomson, “Hist. of Chemistry,” Vol. II. pp. 251, 252;
Matteucci, “Traité des phénomènes,” etc., Part I. p. 7; the
Address of M. Gavarret made in 1848 before the Paris Medical
Faculty; J. C. I. A. Creve’s treatise on Galvanism (“Jour. de
la Soc. de Méd.,” Vol. XVIII. p. 216); “Mém. de la Soc. Méd.
d’Emul.,” Vol. I. p. 236); Biot et Cuvier (_Ann. de Ch._, Vol.
XXXIX. p. 247); A. Richerand (“Mém. de la Soc. Méd. d’Em.” Vol.
III. p. 311); “Opus. Scelt.,” Vol. XV. p. 113; “Giornale Fis.
Med.,” Vol. II. pp. 115, 131 (letter of B. Carminati); Marsiglio
Landriani, “Lettera,” etc., 1776; Lettre d’un ami au Comte
Prosper Albo (“Bibl. de Turin,” 1792, Vol. I. p. 261; _Jour.
de Phys._, Tome XLI. P. 57); “Comment Bonon. Scient.,” Vol.
VII. p. 363; account of the experiments made by MM. Cortambert
and Gaillard, reported in “Mém. de la Soc. Méd. d’Em.,” Vol.
I. pp. 232, 235; G. Klein’s “Dissert. de Métal,” etc., Maintz,
1794; Ostwald’s _Klassiker_, No. 52, p. 4; C. H. Wilkinson,
“Elements of Galvanism,” etc., London, 1804, 2 Vols. _passim_;
Wm. C. Wells, “Obs. on the Influence,” etc. (_Phil. Trans._,
1795, Pt. XI. p. 246); E. G. Robertson (_An. de Ch._, 1801, Vol.
XXXVII. p. 132; _Jour. de Paris_, 10, 15 and 17 Fructidor de
l’An. VIII); Paul Louis Simon, “Beschreibung neuengalvanisch,”
etc., “Resultate,” etc., and “Versuche,” etc., all published in
1801 (L. W. Gilbert’s _Annalen_, 1801, Book V, _An. de Chimie_,
No. 121, p. 106); L. W. Gilbert’s Book VI of the _Annalen_,
containing the “Memoirs on Galvanism,” by J. L. Boeckmann, L. A.
von Arnim, Paul Erman, M. Gruner and C. H. Pfaff; C. Dupuytren,
“Faits Particuliers,” etc., 1801; J. B. Trommsdorff, “Expér.
Galv.,” 1801; M. Rouppe’s letter of Aug. 28, 1801, in Van Mons’
_Jour. de Ch._, Vol. I. pp. 106, 108; M. Bichat (Sue, “Hist. du
Galv.,” II. p. 216); A. M. Vassalli-Eandi (_Jour. de Phys._,
Frimaire, An. X. p. 476); C. F. Hellwag and M. Jacobi fils,
“Erfahrungen,” etc., 1802; M. le Comte de Pusckin’s experiments
on Galvanism, made Sept. and Dec. 1801, with a _colonne
tournante_ (Sue, “Hist. du Galv.,” Vol. II. pp. 257, 258); Al.
Volta, in _Jour. de Leipzig_, and in “Comment ... Med. gestis,”
1792; Johann Mayer, “Abh. ... Galvani, Valli, Carminati u. Volta
...” Prag, 1793); Junoblowiskiana Society (“Comment ... Med.
gestis,” 1793); “Imperial Dictionary of Universal Biography,”
Wm. McKenzie London, n. d., Vol. II. p. 546; M. Cortambert
(“Mém ... Soc. ... d’Emul.,” I. p. 232); M. Payssé (“Jour. de
la Soc. des Pharm.,” first year, p. 100); Geo. Couvier (_Jour.
de Physique_, Vol. VII. p. 318; “Mém. des Soc. Sav. et Lit.,”
Vol. I. p. 132), 1801; C. Mathieu (“Rec. de la Soc. d’Agr. ...
d’Autun,” An. X. p. 21), 1802; Ponton d’Amécourt, “Exposé du
Galvanisme,” Paris, 1803; Joseph Weber’s works, published in
1802–1803, 1815, 1816, and those of J. K. F. Hauff, Marburg
and Leipzig, 1803, 1804; M. Curtet (_Jour. de Van Mons._, No.
VI. p. 272; _Jour. de Physique_, An. XI. p. 54), 1803; William
Meade (“On the origin and progress of Galvanism”), Dublin, 1805;
J. C. Reil (_Jour. de Van Mons._, No. IV. p. 104; Sue, “Hist.
du Galv.,” Vol. IV. p. 26); J. A. Heidmann (_Phil. Mag._, Vol.
XXVIII. p. 97), 1807; Sir Richard Phillips, “Electricity and
Galvanism explained ...” (_Phil. Mag._, Vol. LVI. p. 195),
London, 1820; B. G. Sage, “Recherches ... Galvanisme”; Leopold
Nobili, “Sur le courant....” Genève, 1827.

=A.D. 1786.=--Hemmer (J. J.), celebrated physician and secretary of the Meteor. Society of Mannheim, gives, in the “Transactions of the Electoral Society,” an account of what have been pronounced the most complete series of experiments ever made upon the electricity of the human body. They absolutely show that the human subject possesses no species of electrical organs which are under the regulation of the will. Of his many observations, the following are worth recording: He found that the electricity of the body is common to all ages and sexes; that its intensity and character often vary in the same body (in 2422 experiments, it was 1252 times positive, 771 times negative and 399 times imperceptible); that the electricity of the body is naturally positive, it being always so when subject to no violent exertion, and that when the body is subjected to sudden or violent motion the electricity becomes negative, the case also when the body experiences either cold or extreme lassitude.

REFERENCES.--“Encycl. Brit.,” Vol. VIII, 1855, p. 571;
“Rheinische Beiträgen zur Gelehrsamkeit” for 1781, Fifth Book,
pp. 428–466; Van Swinden, “Recueil,” etc., La Haye, 1784, Vols.
I and II _passim_; “Observ. sur la Phys.,” July, 1780; _Phil.
Mag._, 1799, Vol. V. pp. 1, 140; “Comment. Acad. Theod.-Palat.,”
Vols. IV, V and VI of _Phys._; “Mém. de l’Acad. de Mannheim,”
Vol. IV; “Pfalzbayr. Beiträge” for 1782.

=A.D. 1787.=--Lomond--Lomont--(Claude Jean-Baptiste), a very capable French machinist, and “one who has a genius for invention,” is the first to introduce a successful electric telegraph consisting of but one wire. Of this the following account appears under date Oct. 16, 1787, in Arthur Young’s “Voyage Agronomique en France” (“Travels”), fourth edition, Vol. I. p. 79: “You write two or three words on a paper; he takes it with him into an adjoining room and turns a machine in a cylinder case, on the top of which is an electrometer having a pretty little ball of pith of a quill suspended by a silk thread; a brass wire connects it to a similar cylinder and electrometer in a distant apartment, and his wife, on observing the movements of the corresponding ball, writes the words which it indicates. From this it appears that he (Lomond) has made an alphabet of motions. As the length of the brass wire makes no difference in the effect, you could correspond with it at a great distance, as, for example, with a besieged city or for objects of much more importance. Whatever be the use that shall be made of it, the discovery is an admirable one.”

REFERENCES.--Ed. Highton, “Elec. Tel.,” 1852, p. 38; Sabine,
“Elec. Tel.,” pp. 10–11; Shaffner, “Manual,” pp. 132, 133;
Vail’s “History,” etc., p. 121; “Appleton’s Encycl.,” 1871, Vol.
XV. p. 335.

=A.D. 1787.=--Brard (Cyprien Prosper), French mineralogist, first observes that some crystals of axinite (consisting mainly of silica, alumina, lime and peroxide of iron) become electric by heat.

REFERENCES.--Gmelin, article “Electricity,” etc., Vol. I. p.
319; Larousse, “Dict. Univ.,” Vol. II. p. 1205; Thomas, “Dict.
of Biog.,” Vol. I. p. 429; “Enc. Brit.,” 8th ed., Vol. VIII. p.
530; Brard, “Manuel du Minéralogiste,” etc., Bordeaux Academy of
Sciences Report for 1829, p. 39, and for 1838, p. 84--the latter
containing M. Hatchett’s observations on one of M. Brard’s
meteorolites.

=A.D. 1787.=--Haüy (Le Père René Just), native of Picardie and member of the Académie Royale des Sciences, publishes an abridgment of the doctrines of Æpinus (at A.D. 1759) under the title of “Exposition raisonnée de la Théorie de l’Électricité et du Magnétisme.” He was doubtless the first to observe that in all minerals the pyro-electric state has an important connection with the want of symmetry of the crystals, and no proof of the extent to which he directed his investigations in that line can more readily be had than by consulting general “Encyclopædia” articles relative to the pyro-electricity of boracite (borate of magnesia), of prehnite (silica, alumina and lime), of mesotype (hydrated silicate of alumina and of lime or of soda), of sphene (silica, titanic acid and lime), calamine (silicate of zinc) and of Siberian topaz.

At pp. 480, 481 of his “Outline of the Sciences,” etc., London, 1830, Dr. Thomas Thomson states:

“There is a hill of sulphate of lime, called Kalkberg, situated near Lunebourg, in the duchy of Brunswick, in which small cubic crystals are found. These cubes are white, have a specific gravity of 2·566, and are composed of two atoms of boracic acid combined with one atom of magnesia. They are distinguished among mineralogists by the name of _boracite_. If we examine the cubic crystals of boracite, we shall find that only four of the solid angles are complete, constituting alternate angles placed at the extremity of two opposite diagonals at the upper and lower surface of the cube. The other four solid angles are replaced by small equilateral triangles. When the boracite is heated all the perfect solid angles become charged with _negative_ electricity, while all the angles replaced by equilateral triangles become charged with _positive_ electricity. So that the boracite has eight poles: four positive and four negative. Those are obviously the extremities of four diagonals connecting the solid angles with each other. One extremity of each of these diagonals is charged with positive and the other extremity with negative electricity. In general, the electricity of boracite is not so strong as that of the _tourmaline_.” This curious law of the excitability of the boracite and of its eight poles was discovered by Haüy in 1791 (Haüy’s “Minéralogie,” 260, second edition).

_Axinite_, _mesotype_, and the _silicate of zinc_ are also minerals which become electric when heated, and which, like the _tourmaline_, exhibit two opposite poles, the one positive, the other negative. It is not every crystal of axinite and mesotype which possesses this property, but such only as are unsymmetrical, that is to say, such as have extremities of different shapes. No doubt this remark applies also to the silicate of zinc; though as the crystals of that mineral are usually acicular it is not so easy to determine by observation the degree of symmetry which they may possess.

The _topaz_, _prehnite_, and the titaniferous mineral called _sphene_ are also capable of being excited by heat, and have two opposite poles like those already mentioned.

Haüy also made the most extensive and accurate observations known upon the development of electricity in minerals by friction. Detailed lists of the different classes of minerals, as well as the conclusions arrived at through various experiments, are given in the “Encyclopedia Britannica,” Vol. VIII, 1855, pp. 538, 539, while at pp. 529 and 558 of the same work are to be found accounts of his observations on the electricity of the _tourmaline_, as well as a description of the different electroscopes employed in his many experiments.

REFERENCES.--Priestley, “History of Electricity,” 1767, pp.
314–326; Gmelin’s “Chemistry,” Vol. I. p. 319; Noad, “Manual,”
pp. 27–31; also article “Electricity” in “Library Useful
Knowledge,” pp. 3, 54, 56; M. Lister, “Collection Académique,”
Tome VI; “Société Philomathique,” An. V. p. 34; An. XII. p. 191;
“Mém. du Museum d’Hist. Nat.,” Vol. III; “Mém. de l’lnstitut,”
An. IV. tome i., “Sciences Math. et Phys.” p. 49; “Mém. de
l’Académie,” 1785, Mem. p. 206; _Philosophical Magazine_, Vols.
XX. p. 120; XXXVIII. p. 81; Thomas Thomson, “Hist. of the
Roy. Soc.,” London, 1812, pp. 180, etc.; Young’s “Lectures,”
London, 1807, Vol. II; Haüy, “Traité Élémentaire de Physique,”
Chap VII, “Magnetism”; Experiments of J. L. Treméry (author of
“Observations sur les Aimants Elliptiques,” recorded in _Journal
des Mines_, Vol. VI for 1797, also in _Jour. de Phys._, Vols.
XLVIII and LIV) and of M. De Nelis, some of whose observations
are given in the _Phil. Mag._, Vol. XLVIII. p. 127, and in the
_Jour. de Phys._, Vols. LXI. p. 45; LXII. p. 150; LXIII. p. 147;
LXIV. p. 130; LXVI. pp. 336, 456, as shown and illustrated at
pp. 153–162 of Delaunay’s “Manuel,” etc., of 1809; “Séances de
l’Acad. de Bordeaux” for 1835, giving M. Vallot’s report on the
difference existing between the chalcedony and the tourmaline.
Regarding the latter, consult S. Rinmann (“K. Schwed. Akad.
Abh.,” XXVIII. pp. 46, 114); C. Rammelsberg, “Die Zuzam ... und
Feldspaths”; Mr. Magellan’s edition of Cronstedt’s Mineralogy
for Steigliz’s tourmaline; Cesare G. Pozzi, on the tourmaline;
H. Von Meyer (“Archiv. ... Ges. Natural,” XIV. 3, p. 342); M.
Lechman (Berlin Academy Reports); Carl Von Linné (Linnæus),
“Flora Zeylanica,” Stockholm, 1747; M. Leymerie (Toulouse Acad.
Reports); Brewster, “Journal” I. p. 208; J. K. Wilcke (“Vetensk.
Akad. Handl.,” 1766 and 1768); Jos. Muller, “Schreiben ...
Tourmaline,” Wien, 1773; F. J. Muller von Reichenstein, “Nachr.
... an Born,” Wien, 1778; H. B. de Saussure (“Jour. de Paris”),
1784; Louis Delaunay’s letter on the tourmaline, 1782; D. G.
Fischer’s works, published at Mosk, 1813, 1818; J. D. Forbes
(“Edin. Trans.,” Vol. XIII), 1834.

=A.D. 1787.=--Charles (Jacques Alexandre César), a singularly able French physicist and experimentalist, who became the Secretary of the Académie des Sciences, relates many of his electrical experiments in the thirtieth volume of the _Journal de Physique_.

He was one of the first to study and develop the theories of Franklin, who, in company with Volta, frequently attended the brilliant lectures which Charles was enabled to give in what was then considered the most complete philosophical laboratory of Europe. In many of his experiments on atmospherical electricity, Charles has been known to produce thousands of sparks, beams or flashes, which exceeded 12 feet in length and which made reports similar to those of fire-arms. The French Academy endorsed the opinion given the Minister of War by Charles to the effect that “a conductor will effectually protect a circular space whose radius is twice the length of the rod.”

Charles invented the megascope and was the first to make an ascension in a hydrogen balloon, which he did in company with M. Robert on the 1st of December (not on the 2nd of August) 1783, ten days after the first trip made by Pilatre de Rozier and Comte d’Arlandes in a Montgolfière from the Paris Bois de Boulogne.

REFERENCES.--“Biographie Générale,” Vol. IX. pp. 929–933;
Larousse, “Dict. Univ.,” Vol. III. p. 1020; _Journal de
Physique_ for 1791, p. 63; “Mémoires de l’Acad. des Sciences”
for 1828; George Adams, “Lectures on Nat. and Exp. Philosophy,”
London, 1799, Vol. III. pp. 462–464; Edin. Encycl., 1813,
article “Aeronautics,” Vol. I. p. 160, “Franklin in France,”
1888, Part II. pp. 256, 270, 276–280; M. Veau Delaunay,
Introduction to his “Manuel,” etc., Paris, 1809, pp. 19, 25 and
61–63; also pp. 23, 68, 92, 96, 122, 176 and 214.

=A.D. 1787.=--Mann (Théodore Augustin), Abbé, Flemish writer and antiquary, becomes perpetual secretary of the Brussels Academy of Sciences ten years after leaving the Nieuport Monastery (1777), and is charged with the duty of making meteorological observations, which are regularly transmitted to the Mannheim Academy officials, who receive similar reports regularly from different parts of Europe and publish them under the title of “Ephémérides Météorologiques.”

His many investigations made with electrical machines are embraced in the last-named publication and are also alluded to in his “Marées Aériennes,” etc., which appeared in Brussels during the year 1792.

REFERENCES.--“Biog. Générale,” Tome XXXIII. p. 231; Larousse,
“Dict. Universel,” Tome X. p. 1085; _Phil. Mag._, Vol. IV. p.
337; “Comm. Ac. Theod. Pal.,” 1790, Vol. VI. p. 82.

=A.D. 1787.=--Bennet (Rev. Abraham), F.R.S., first describes in the _Philosophical Transactions_ for this year, pp. 26–32, the gold-leaf electroscope which bears his name and which is considered the most sensitive and the most important of all known instruments for detecting the presence of electricity. It consists of a glass cylinder which is covered with a projecting brass cap, made flat in order to receive upon it whatever article or substance is to be electrified, and having an opening for the insertion of wires and of a metallic point to collect the electricity of the atmosphere. The interior of the cap holds a tube which carries two strips of gold leaf in lieu of the customary wires or threads, and upon two opposite sides of the interior of the cylinder are pasted two pieces of tinfoil directly facing the gold-leaf strips. The cap is turned around until the strips hang parallel to the pieces of tinfoil, so that any electricity present will cause the strips to diverge and make them strike the tinfoil, which will carry the electricity through the support of the cylinder to the ground.