Bibliographical history of electricity & magnetism, chronologically arranged

by Unknown

Gmelin Family

This family, which, through four generations, has been continuously distinguished for its valuable contributions to chemistry as well as to the natural and medical sciences, deserves equally well here of such a special mention as was accorded to the Bernoulli and Cassini families, under dates A.D. 1700 and 1782–1791.

Johann Georg Gmelin (1674–1728), a very able chemist and pharmaceutist of Tübingen, was the father of:

Johann Conrad Gmelin (1707–1759), physician and author in the same city of Tübingen.

Johann Georg Gmelin (1709–1755), distinguished naturalist and chemist, who graduated as M.D. in his nineteenth year, became a member of the St. Petersburg Acad. of Sc. and was sent by the Empress Anna, in company with G. A. Müller and other noted scientists, upon a ten years’ exploring expedition through Siberia. He was one of the first explorers of Northern Asia, and a genus of Asiatic plants was named Gmelina after him by Linnæus.

Philip Friedrich Gmelin (1722–1768), Professor of Botany and of Chemistry at Tübingen, author of many scientific monographs.

Samuel Gottlieb Gmelin (1744–1774), elder son of Philip Friedrich, who, like his uncle, graduated M.D. at nineteen and was sent two years later by the Empress Catherine II upon a scientific tour through South-Eastern Russia, is the author of “Historia Fucorum ...” as well as of other contributions which were edited through the famous Pallas. His biographical notice appears in the last volume of the “Reise durch Russland ...” published at St. Petersburg.

Johann Friedrich Gmelin (1748–1804), M.D., succeeded his father, Philip Friedrich, in the chair of chemistry and botany at the Tübingen University, became Professor of Medicine at Göttingen in 1778 and a member of “l’Académie des Curieux de la Nature.” He is the author of the thirteenth edition of Linnæus’ “Systema Naturæ,” which, notwithstanding Cuvier’s severe criticism of it, is said to be the only work which even professes to embrace all the objects of natural history described up to the year 1790 (“Encycl. Brit.,” 1855, Vol. IX. p. 4). He is also the author of “Geschichte der Chemie ...” Göttingen, 1797–1799, and of “Prælectio de col. metal. a Volta ...” (“Commentat. Soc. Gött.” XV (Phys.) for 1800–1803, p. 38). (See J. C. Poggendorff, “Biogr.-Literar. Handwörterbuch,” Vol. I. pp. 914–915.)

His son, Leopold Gmelin (1788–1853), who has already been noticed, practised chemical manipulation in the Tübingen pharmaceutical laboratory of Dr. Christian Gmelin, the son of Johann Conrad, and studied at Göttingen, Vienna and in Italy, after which he became medical and chemical professor at Heidelberg, 1817–1851 (Poggendorff, Vol. I. pp. 915–916).

Ferdinand Gottlob von Gmelin (1782–1848), elder son of Dr. Christian Gmelin, was Professor of Medicine and of Natural History in the Tübingen University, and wrote “Diss. sistens obs. phys. et chem. de electricitate et galvanismo” during 1802 (Poggendorff, Vol. I. pp. 916–917).

Christian Gottlob Gmelin (1792–1860), brother of the last named, M.D., was Professor of Chemistry and Pharmacy at the Tübingen University, and the author of “Experimenta electricitatem ...” 1820; “Uber d. Coagulat. ... d. Electricität” (Schweigger’s “Journal,” Vols. XXXVI for 1822); “Analyse d. turmalins ...” (Schweigger’s “Journal,” Vols. XXXI for 1821 and XXXVIII for 1823—Poggendorff’s “Annalen,” Vol. IX for 1827), as well as of a “Handbuch der Chemie,” published 1858–1861 (Poggendorff, Vol. I. p. 917; Phil. Mag. or Annals, Vol. III. p. 460).

References.—Gmelin and Schaub, “Effets Chimiques de la col. metal ...” (“Magas. Encyclop.,” Vol. VI. p. 201); Eberhard Gmelin’s letter to M. Privy Councillor Hoffmann of Mayence (1787), and his new investigations (1789) on the subject of animal magnetism (“Salzb. Med. Chir. Zeit.,” 1790, I. p. 358); Whewell, “Hist. of the Ind. Sc.,” 1859, Vol. II. p. 348.

A.D. 1819.—Dana (J. F.), M.D. (1793–1827), Chemical Assistant in Harvard University and Lecturer on Chemistry and Pharmacy in Dartmouth College, writes, Jan. 25, 1819, to Prof. Benjamin Silliman concerning his new form of portable electrical battery.

This apparatus, consisting of alternate plates of flat glass and of tinfoil, the sheets of which latter are connected together, is fully described at pp. 292–294, and is illustrated opposite p. 288, Vol. I of Silliman’s American Journal of Science, 1818, wherein it is stated that, while “in a battery of the common form, 2 feet long, 1 foot wide and 10 inches high, containing 18 coated jars, there will be no more than 3500 square inches of coated surface,” a battery of Dana’s construction will have no less than 8000 square inches covered with tinfoil, allowing the sheet of glass and of foil to be a quarter of an inch thick. In a brief description of this apparatus, which appears at p. 468, Vol. V of Tilloch’s Phil. Mag. and Journal, it is stated that a “battery constructed in this way contains, in the bulk of a quarto volume, a very powerful instrument; and when made of glass it is extremely easy, by varnishing the edges, to keep the whole of the inner surfaces from the air, and to retain it in a constant state of dry insulation.”

A.D. 1820.—Oersted—Örsted (Hans Christian), native of Denmark (1770–1851), Professor of Natural Philosophy and founder of the Polytechnic School in Copenhagen, makes known, through a small four-page pamphlet entitled “Experimenta circa effectum conflictus electrici in acum magneticam,” his great discovery of the intimate relation existing between electricity and magnetism (Thomson’s Annals of Philosophy for October 1820, Vol. XVI, first series, pp. 273–276). He thus lays the foundation of the science of electro-magnetism, which subsequently was so materially developed by Ampère and Faraday.

It is said that after taking his doctor’s degree in 1799, he gave much attention to galvanism, and that in the year 1800 he made important discoveries as to the action of acids during the production of galvanic electricity. He was one of the earliest to show the opposite conditions of the poles of the galvanic battery, also that acids and alkalies are produced in proportion as they neutralize each other. Upon his return from a trip to France and Germany, 1801–3, he lectured on electricity and the cognate sciences, publishing thereon a number of essays. (These are to be found, more particularly, in J. H. Voigt’s Magazin, Vol. III. p. 412; Van Mons’ Journal, No. IV. p. 68; the Bulletin of the Société Philomathique, No. LXVII. an. xi. p. 128; A. F. Gehlen’s Neues Allgem. Journal d. Chemie, Vols. III for 1804, VI for 1806, VIII for 1808; Schweigger’s Journal, Vol. XX; Phil. Mag., Vol. XXIII. p. 129; the “Skand. Lit.-Selskabs Skrifter,” Vol. I; “Oversigt over det Kongl. ... Forhandlinger,” 1814–1815; “Nyt Biblioth. f. Physik,” etc., Vol. IX, and in the Journal de Physique as well as in the Journal du Galvanisme.)

He revisited Germany during 1812, and, at the suggestion of Karsten Niebuhr, published in Berlin his work “Ansicht der Chemischen Naturgesetze. ...” (“Inquiry into the identity of chemical and electric forces”), a translation of which was made by M. P. Marcel T. de Serres under the title of “Recherches sur l’Identité. ...” (Fahie, “Hist. of Electric Teleg.,” 1884, pp. 270–273). The last-named work appeared at Paris during 1813, and not, as stated at p. 41, Vol. LVII of the Philosophical Magazine, during 1807, which was the date of the original small German edition.[59]

One of his biographers says that Oersted was lecturing one day to a class of advanced students, when, as a means of testing the soundness of the theory which he had long been meditating, it occurred to him to place a magnetic needle under the influence of a wire uniting the ends of a voltaic battery in a state of activity. “In galvanism,” said he, “the force is more latent than in electricity, and, still more so in magnetism than in galvanism; it is necessary therefore to try whether electricity, in its latent state, will not affect the magnetic needle.” He tried the experiment upon the spot and found that the needle tended to turn at right angles to the wire, thus proving the existence of electro-magnetism, or the relation of electricity and magnetism as mutually productive of each other, and as evidences of a common source of power. Previous to this time the identity of magnetism and electricity had only been suspected. For several months Oersted prosecuted experiments on the subject, and on the 21st of July 1820 promulgated his discovery through the Latin pamphlet above alluded to. Therein he contends that there is always a magnetic circulation around the electric conductor, and that the electric current in accordance with a certain law always exercises determined and similar impressions on the direction of the magnetic needle, even when it does not pass through the needle but near it (the eighth edition of the “Encycl. Britannica,” Fifth Dissertation, pp. 739, 740, 745; and the Sixth Dissertation, pp. 973–976; Schaffner, “Tel. Manual,” 1859, Chap. VIII; Practical Mechanic, Glasgow, 1842, Vol. III. p. 45).

For this discovery, which naturally excited the wonder of the entire scientific world, he received the Copley medal of the English Royal Society, the Dannebrog order of knighthood and numerous testimonials from nearly every quarter of Europe. As observed by Mr. J. D. Forbes (Sixth Disser. “Encycl. Brit.,” Vol. I), “the desideratum of a clear expression of the manifest alliance between electricity and magnetism has been so long and so universally felt that the discovery placed its author in the first rank of scientific men.... The prize of the French Institute, which had been awarded to Davy for his galvanic discoveries, was bestowed upon Oersted.”

Oersted’s experiments were repeated before the French Academy of Sciences by M. De la Rive on Sept. 11, 1820, and, seven days later, as we shall see, Ampère made known the law governing electro-magnetism (Mme. Le Breton, “Hist. et. Appl. de l’Elect.,” Paris, 1884, pp. 72, 73; W. Sturgeon, “Sci. Researches,” Bury, 1850, p. 18; Higg’s Translation of Fontaine’s “Electric Lighting,” London, 1878, p. 54).

The many investigations subsequently carried on by Oersted in different branches of sciences are alluded to in the works named below. Perhaps the most interesting, outside of the ones already spoken of, are those attaching to thermo-electricity which he made in conjunction with Baron Fourier, and independently of Dr. Seebeck.

References.—Eighth “Britannica,” pp. 651 and 652, Vol. XXI, as well as pp. 11 and 12, Vol. XIV of Oersted’s “Efterretning om nogle nye, af Fourier og Oersted ...” Kiobenhaven, 1822–1823, translated into French as mentioned in Vol. XXII of the Annales de Chimie et de Physique; “Oversigt over det Kongl. ...” for 1822–1823 and 1823–1824; Poggendorff, Vol. III. pp. 309–312; “Catal. Sci. Papers Roy. Soc.,” Vol. I. pp. 697–701; Biog. Sketch by P. L. Möller, “Oersted’s Character und Leben,” 1851, also Hauch und Forchammer, 1853; Obituary notice in Jour. Frankl. Inst., 1851, Vol. XXI. p. 358; Humboldt, “Cosmos,” 1849, Vol. I. pp. 182, 185 and the 1819–1820 entry of “Magnetic Observations,” in Vol. V; “Oversigt over det Kongl. danske Videnskabernes Selskabs Fordhandlinger” for 1822, 1832, 1834–1835, 1836–1837, 1840–1842, 1847–1849; Poggendorff’s Annalen, Vol. LIII; “Ursin’s Magaz. f. Kunstnere ...” Vols. I and II; “Dict. of Electromagn.,” 1819; Sturgeon’s Annals of Electricity, Vol. I. p. 121; Hatchett “On the Experim. ... of Oersted and Ampère” (Phil. Mag., Vol. LVII. p. 40), Phil. Mag., Vols. LVI. p. 394; LVII. pp. 47–49; LIX. p. 462; Phil. Mag. or Annals, Vol. VIII. p. 230; Annales de Chimie for Aug. 1820, p. 244; S. S. Eyck, “Over de magnetische ...” (Bibl. Univ., 1821); Translation by H. Sebald, of H. C. Oersted’s “Leben,” 1853; Michaud, “Biog. Univ.,” Vol. XXXI. p. 196; P. L. Möller, “Der Geist in der Natur” (”The Spirit in Nature”); Elie de Beaumont, “Memoir of Oersted” (“Smith. Rep.” for 1863); Gilbert’s Annalen, Vol. LXVI. p. 295, 1820; Callisen, “Medicinisches Schriftseller-Lexikon”; W. Sturgeon’s “Sci. Researches,” Bury, 1850, p. 8 (for 1807), and pp. 9–12 for English version of Oersted’s pamphlet which was translated in German in Vol. XXIX of Schweigger’s “Journal,” as well as in Vol. LXVI of Gilbert’s Annalen, and which appeared in French in Vol. XIV of the Annales de Chimie et de Physique for 1820, as well as in Vol. II. pp. 1–6 of “Collection de Mémoires relatifs à la Physique,” Paris, 1885. See also “Biogr. Gén.,” Vol. XXXVIII. pp. 522–535; “Göttinger Gelehrte Anz.,” No. 171; Sturgeon’s “Sc. Researches,” pp. 17, 18, 28, 415; Thomson’s “Annals of Philosophy,” Vol. XVI. p. 375 for second series of observations; Van Marum on “Franklin’s Theory of Electricity,” pp. 440–453; “Galvanism,” by Mr. John Murray, p. 467; “Note sur les expériences ... de Oersted, Ampère, Arago, et Biot,” (Annales des Mines, 1820); L. Turnbull, “Elec. Mag. Tel.,” 1853, pp. 45, 221; J. F. W. Herschel’s “Preliminary Discourse,” 1855, pp. 244, 255; Fahie, “Hist. Elec. Tel.,” 1884, pp. 270–275, Harris, “Rud. Elec.,” 1853, p. 171; Ostwald’s Klassiker, No. 63 and “Elektrochemie,” 1896, p. 67; Mrs. Somerville, “Con. of Phys. Sci.,” 1846, p. 314; Noad, “Manual,” p. 642; “Lib. Useful Know.” (El Magn.), pp. 4, 79; Lardner’s “Lectures,” 1859, Vol. II. p. 119; Tomlinson’s “Cycl. Useful Arts,” Vol. I. p. 559; Ure’s “Dict. of Arts,” 1878, Vol. II. p. 233; Henry Martin’s article in Johnson’s “New Cyclopædia,” 1877, Vol. I. pp. 1512, 1514; “Nyt Biblioth. f. Physik,” Band I auch Scherer’s Nord. Arch., II; “Tidskrift f. Natur ...” I 1822: Schumacher’s “Astron. Jahrbuch” for 1838; L. Magrini, “Nuovo metodo ...” Padova, 1836; Boisgeraud “On the Action of the Voltaic Pile ...” (Phil. Mag., Vol. LVII. p. 203); Sci. Am. Suppl., No. 454, p. 7241; Schweigger’s Journal, Vols. XXXII, XXXIII, LII; Figuier, “Expos. et Hist.,” 1857, Vol. IV. p. 393; “Engl. Cycl.,” “Arts and Sci.,” Vol. III. p. 782; Brande’s “Man. of Chem.,” London, 1848, Vol. I. p. 248; Prime’s “Life of Morse,” pp. 264, 451; Dr. Henry’s “Elm. of Exper. Chem.,” London, 1823, Vol. I. pp. 193–203; Jour. of the Frankl. Inst. for 1851, Vol. XXI. p. 403; “La Lumière Electrique” for Mar. 19, 1887, p. 593, and for Oct. 31, 1891, pp. 201, etc.: Sir William Thomson, “Math. Papers,” reprint, etc., 1872; “Encyl. Metrop.” (Elect. Mag.,); G. B. Prescott, “Elect. and the El. Tel.,” 1885, Vol. I. p. 91; “Smithsonian Report” for 1878, pp. 272, 273, note; Bacelli (L. G.), “Risultati ...” Milano, 1821; “Bibl. Britan.,” Vol. XVII, N.S. p. 181; Vol. XVIII, N.S. p. 3; “Edin. Phil. Journal,” Vol. X. p. 203; “Journal of the Soc. of Tel. Eng.,” 1876, Vol. V. pp. 459–464, for a verbatim copy of Oersted’s original communication on his discovery of electro-magnetism, and pp. 464–469 for a translation thereof by the Rev. J. E. Kempe under the title of “Experiments on the effect of electrical action on the Magnetic Needle.” For the interesting electro-magnetic experiments of J. Tatum, at this same period, consult the Phil. Mag., Vol. LVII, 1821, p. 446; Vol. LXI, 1823, p. 241; Vol. LXII, 1823, p. 107, and, for additional investigation, the Vols. XLVII and LI for years 1816 and 1818.

A.D. 1820.—On Oct. 9, M. Boisgeraud, Jr., reads, before the French Académie des Sciences, a paper concerning many of his experiments, which prove to be merely variations of those previously made by Oersted.

He observed that connecting wires, or arcs, placed anywhere in the battery, affect the needle, and he noticed the difference of intensity in the effects produced when electrical conductors are employed to complete the circuit. He proposed to ascertain the conducting power of different substances by placing them in one of the arcs, cells or divisions of the battery, and bringing the magnetic needle, or Ampère’s galvanometer, toward another arc, viz. to the wire or other connecting body used to complete the circuit in the battery. With regard to the positions of the needle and wire, as observed by Boisgeraud, they are all confirmatory of Prof. Oersted’s statement (“Ency. Met.” (Electro.-Mag.), Vol. IV. p. 6).

One month later, Nov. 9, 1820, Boisgeraud reads, before the same Académie, his paper “On the Action of the Voltaic Pile upon the Magnetic Needle,” which will be found on pp. 203–206 and 257, 258, Vol. LVII of the Philosophical Magazine.

A.D. 1820.—Banks (Sir Joseph) (1743–1820), a very eminent English naturalist and traveller, to whom reference has been made under the A.D. 1775 date, deserves mention here were it alone for the fact that while occupying the presidential chair of the Roy. Soc., during the extraordinary long and unequalled period of over forty-two years (1777, date of Sir John Pringle’s retirement, to 1820, the date of President Banks’ death) he was instrumental in bringing prominently before the world many of the most important discoveries and experiments known in the annals of magnetism and electricity.

Sir Joseph Banks was succeeded in the presidency of the Royal Society by William Hyde Wollaston, M.D., June 29, 1820, and by Sir Humphry Davy, Bart., Nov. 30, 1820, the last named holding the office seven years (R. Weld, “Hist. Roy. Soc.,” 1848, Vol. II. p. 359). Banks and Dr. Solander, the pupil of Linnæus, had sailed (1768–1771) with Captain Cook in his voyage around the globe, in the capacity of naturalists, and afterwards (1772) visited Iceland, where they made many important discoveries. In 1781 Banks was created a baronet; he received the Order of the Bath in 1795 and subsequently had many honours conferred upon him by different English and foreign societies. It is said that he was never known to be appealed to in vain by men of science, either for pecuniary assistance or for the use of his extensive library.

References.—Tilloch’s Phil. Mag. for 1820, Vol. LVI. pp. 40–46; “Cat. Sci. Papers Roy. Soc.,” Vol. I. p. 176; Dr. Thomas Thomson, “Hist. Roy. Soc.,” London, 1812, p. 12; Gentleman’s Magazine for 1771, 1772 and 1820; “Biog. Univ.,” Vol. LVII, Suppl. p. 101; Larousse, “Dict. Univ.,” Vol. II. p. 155; “Eloge Historique de Mr. J. Banks, lu à la Séance de l’Académie Royale des Sciences, le 2 Avril 1821”; Sir Everard Home, “Hunterian Oration,” Feb. 14, 1822. See besides, the Phil. Mag., Vol. LVI. pp. 161–174, 241–257, for “A review of some of the leading points in the official character and proceedings of the late President of the Royal Society,” contrasting the respective personal merits and achievements of Sir John Pringle and of Sir Joseph Banks; “Lives of Men of Letters and Science,” by Henry, Lord Brougham, Philad., 1846, pp. 199–229, 294–295.

A.D. 1820.—Barlow (Peter), F.R.S. (1776–1827), who taught mathematics at the Military Academy of Woolwich from 1806 to 1847, brings out the first edition of his “Essay on Magnetic Attractions, Particularly as Respects the Deviation of the Compass on Shipboard Occasioned by the Local Influence of the Guns, etc., with an Easy Practical Method of Observing the Same in all Parts of the World.” One of his biographers states that through this valuable publication, which received the Parliamentary reward from the then existing Board of Longitude, as well as presents from the Russian Emperor, he was the first to reduce to strictly mathematical principles the method of compensating compass errors in vessels (Edin. Jour. of Sci., London, 1826, Vols. I. pp. 181, 182; II. p. 379).

This work contains the results of the many experiments to ascertain the influence of spherical and other masses of iron upon the needle, which Barlow instituted, more particularly after Prof. Hansteen’s investigations became generally known. Sir David Brewster details Barlow’s work in the “Encycl. Brit.,” and refers to the separate observations of Mr. Wm. Wales (at A.D. 1774), Mr. Downie (at A.D. 1790), Captain Flinders (at A.D. 1801), and Charles Bonnycastle (at A.D. 1820), mentioning the fact that it is to Mr. W. Bain we owe the distinct establishment and explanation of the source of error in the compass arising from the attraction of all the iron on board of ships. The small 140-page book which Mr. Bain published on the subject in 1817 is entitled “An Essay on the Variation of the Compass, Showing how Far it is Influenced by a Change in the Direction of the Ship’s Head, with an Exposition of the Dangers Arising to Navigators from not Allowing for this Change of Variation.” Brewster remarks that additional light was thrown upon Mr. Bain’s observations by Captains Ross, Parry and Sabine, but that we owe to Prof. Barlow alone a series of brilliant experiments which terminated in his invention of the neutralizing plate for correcting in perfect manner this source of error in the compass (Noad’s “Manual,” pp. 531, 532; Olmstead’s “Introduct. to Nat. Hist.,” 1835, pp. 206, 210). The simple contrivance therein alluded to is described and illustrated at pp. 9 and 90–91 of the “Britannica,” article on “Navigation,” and may briefly be said to consist of only a thin circular plate of iron placed in a vertical position immediately behind the binnacle or compass (Fifth Dissertation of “Britannica,” Vol. I. p. 745, and article “Seamanship,” in Vol. XX. p. 27). Such plates were immediately tried in all parts of the world and were at once applied to the English vessels “Conway,” “Leven” and “Barracouta” (Trans. Soc. of Arts for 1821, Vol. XXXIX. pp. 76–100; Harris’ “Rud. Mag.,” III. pp. 69–76; John Farrar, “Elem. of El. ...” 1826, pp. 376–383; Westminster Review for April 1825; “Encycl. Metropol.,” Vol. III (Magnetism), pp. 743, 799).

For Mr. Barlow’s experiments on the influence of rotation upon magnetic and non-magnetic bodies, the result of which was communicated by him to the Royal Society, April, 14, 1825, six days before the receipt of S. H. Christie’s paper “On the Magnetism of Iron, Arising from its Rotation,” communicated by J. F. W. Herschel, see pp. 10, 33, 34, of the “Britannica,” Vol. XIV above referred to (Edin. Jour. of Science, 1826, Vols. III. p. 372, and V. p. 214. Consult also, J. Farrar, “Elem. of El.,” 1826, pp. 387–395. For his extensive observations regarding the influence of heat on magnetism and relative to the variation, as well as for the mode of constructing his artificial magnets, consult the same volume of the “Britannica,” at pp. 35, 36, 50–53 et seq. and p. 73. See likewise, for the variation, Dr. Thomas Thomson’s “Outline of the Sciences,” London, 1830, pp. 549–556; Harris, “Rud. Mag.,” I, II. pp. 152–153. For Samuel Hunter Christie, consult “Abstracts of Papers ... Roy. Soc.,” Vol. II. pp. 197, 225, 243, 251, 270, 305, 321, 347 and 351).

The new variation chart which Prof. Barlow constructed and in which he embraced the magnetic observations made in 1832 by Sir James Ross, R.N., is described and illustrated in Phil. Trans. for 1833, pp. 667–675, Plates XVII, XVIII. He remarks that the very spot where his officer found the needle perpendicular, “that is, the pole itself, is precisely that point in my globe and chart in which, by supposing all the lines to meet, the several curves would best preserve their unity of character, both separately and conjointly as a system” (eighth “Britan.,” Vol. XIV, note, p. 50; Noad, “Manual,” p. 617; D. Olmstead, “Intr. to Nat. Phil.,” 1835, p. 192).

Mr. Barlow’s electro-magnetic globe was exhibited by Dr. Birkbeck in his lectures on “Electro-Magnetism” at the London Institution, May 26, 1824. (Its construction is fully described, more particularly, at p. 65 of the English “Encycl. Brit.” (Magnetism); p. 91 of the “Lib. of Useful Knowledge” (Electro-Magnetism); pp. 139–140, Vol. I of the Edin. Jour. of Science, London, 1826, and pp. 120–122, Part III of Harris’ “Rud. Mag.”) Its purpose was to show that what had hitherto been considered as the magnetism of the earth might be only modified electricity, and it was also intended to illustrate the theory advanced by M. Ampère, who, as is well known, attributed all magnetic phenomena to electric currents. In the words of Dr. Brewster:

“Barlow considers it as probable that magnetism as a distinct quality has no existence in Nature. As all the phenomena of terrestrial magnetism can be explained on the supposition that the magnetic power resides on its surface, it occurred to Mr. Barlow that if he could distribute over the surface of an artificial globe a series of galvanic currents in such a way that their tangential power should everywhere give a corresponding direction to the needle, this globe would exhibit, while under electrical induction, all the magnetic phenomena of the earth upon a needle freely suspended above it. Mr. Barlow says ‘he has proved the existence of a force competent to produce all the phenomena without the aid of any body usually called magnetic,’ yet he acknowledges that ‘we have no idea how such a system of currents can have existence on the earth, because, to produce them, we have been obliged to employ a particular arrangement of metals, acids, and conductors.’”

Barlow was the first to test the practicability of Ampère’s suggestion that by sending the galvanic current through long wires connecting two distant stations, the deflections of enclosed magnetic needles would constitute very simple and efficient signals for an instantaneous telegraph (Ann. de Chimie et de Phys., 1820, Vol. XV. pp. 72, 73). He has thus stated the result: “In a very early stage of electro-magnetic experiments, it had been suggested (by Laplace, Ampère and others) that an instantaneous telegraph might be established by means of conducting wires and compasses. The details of this contrivance are so obvious, and the principle on which it is founded so well understood, that there was only one question which could render the result doubtful; and this was, is there any diminution of effect by lengthening the conducting wires? It had been said that the electric fluid from a common (tinfoil) electric battery had been transmitted through a wire four miles in length without any sensible diminution of effect, and, to every appearance, instantaneously; and if this should be found to be the case with the galvanic circuit, then no question could be entertained of the practicability and utility of the suggestion above adverted to. I was therefore induced to make the trial; but I found such a sensible diminution with only 200 feet of wire, as at once to convince me of the impracticability of the scheme. It led me, however, to an inquiry as to the cause of the diminution, and the laws by which it is governed.” This passage is quoted in “Smithsonian Report” for 1878, p. 279; Fahie, “Hist. El. Tel.,” p. 306; “Memor. of Jos. Henry,” 1880, pp. 223, 224, the last named containing the following footnote: “On the Laws of Electro-Magnetic Action,” Edinburgh Philosophical Journal, Jan., 1825, Vol. XII. pp. 105–113:

“In explanation and justification of this discouraging judgment from so high an authority in magnetics, it must be remembered that both in the galvanometer and in the electro-magnet, the coil best calculated to produce large effects was that of least resistance; which unfortunately was not that best adapted to a long circuit. On the other hand the most efficient magnet or galvanometer was not found to be improved in result by increasing the number of galvanic elements. Barlow in his inquiry as to the law of diminution was led (erroneously) to regard the resistance of the conducting wire as increasing in the ratio of the square root of its length” (pp. 110, 111 of the last-cited “Journal.)”]

Mr. Taylor justly adds that subsequent experiments have proved Ohm’s law (announced three years after Barlow’s) of a simple ratio of resistance to length as approximately correct.

References.—G. B. Prescott, “The Speaking Telephone,” 1879, II; Sci. Am. Supp., Nos. 405, p. 6466; 453, p. 7235; 547, p. 8735: “Mem. of Jos. Henry,” 1880, pp. 83, 94, 144, 485, 487. See also, Poggendorff, Vol. I. pp. 102, 103; Whewell, “Hist. Ind. Sciences,” 1859, Vol. II. pp. 223, 224, 245, 254, 616; “Lib. Useful Knowledge” (Magnetism), p. 86 and (El. Mag.), pp. 7, 18, 22, 28; Sturgeon’s “Sci. Researches,” Bury, 1850, pp. 26, 29, 31, 298; Humboldt, “Cosmos,” 1849, Vol. I. p. 183; Mrs. Somerville, “On the Earth not a Real Magnet,” in the “Conn. of the Phys. Sci.,”; Phil. Mag., Vols. LV. p. 446; LX. pp. 241, 343; LXII. p. 321; Harris, “Rud. Mag.,” Part III. pp. 114–116; “Encycl. Metropol.,” Vol. IV (Elect. Mag.), pp. 1–40; “Abstracts of papers ... Roy. Soc.,” Vol. II. pp. 164, 197, 241, 318; “Cat. Sc. Papers ... Roy. Soc.,” Vol. I. pp. 182–184; “Bibl. Britan.,” Vol. XX, N.S. p. 127; “Edin. Phil. Journal,” 1824, Vol. X. p. 184 (alludes to papers of Barlow and Christie in Phil. Trans. for 1823, Part II).

Mr. Wm. Henry Barlow, second son of Peter Barlow, is the author of a treatise, “On the spontaneous electrical currents observed in the wires of the electric telegraph,” which was published in London during 1849 and appeared in Part I of the Phil. Trans., for that year. He is also the inventor of a new electrical machine alluded to herein at Hare (A.D. 1819), also at p. 130 of the “Annual of Sc. Disc.,” at pp. 76–77 of Noad’s “Manual,” and at p. 428, Vol. XXXVII of the “Philosophical Magazine.”

A.D. 1820.—Laplace (Pierre Simon, Marquis de) (1749–1827), a very distinguished French astronomer and mathematician, suggests for telegraphic purposes the employment of magnetic needles suspended in multipliers of wire, in place of the voltameters of Sömmering, and on the 2nd of October 1820 his theory is thus explained by Ampère in a paper read before the French Academy of Sciences:

“According to the success of the experiment to which Laplace drew my attention, one could, by means of as many pairs of live wires and magnetic needles as there are letters of the alphabet, and by placing each letter on a separate needle, establish, by the aid of a distant pile, and which could be made to communicate by its two extremities with those of each pair of conductors, a sort of telegraph, which would be capable of indicating all the details that one would wish to transmit through any number of obstacles to a distant observer. By adapting to the battery a keyboard whose keys were each marked with the same letters and establishing connection (with the various wires) by their depression, this means of correspondence could be established with great facility, and would only occupy the time necessary for pressing down the keys at the one station and to read off the letters from the deflected needles at the other.”

Laplace is, perhaps, best known by his “Traité de Mécanique Céleste,” the sixteen books and supplements to which are by many considered, next to Newton’s “Principia,” the greatest of astronomical works; a book which has been truly said to have had no predecessor and which has been called the crowning glory of Laplace’s scientific career. His next important work was the “Théorie Analytique des Probabilités,” the most mathematically profound treatise on the subject which had yet appeared, while his “Système du Monde” was called by Arago “one of the most perfect monuments of the French language.” By Prof. Nichols, Laplace is called “the titanic geometer”; by Mr. Airy “the greatest mathematician of the past age”; by Prof. Forbes “a sort of exemplar or type of the highest class of mathematical natural philosophers of this, or rather the immediately preceding age.”

Laplace also wrote, in conjunction with Lavoisier, a treatise “On the Electricity which Bodies Absorb when Reduced to Vapor” (Mém. de Paris for 1781). Prof. Denison Olmstead, treating of the origin of atmospherical electricity (“Introd. to Nat. Phil.,” 1835, pp. 158, 159), says: “Among the known sources of this agent none seems so probable as the evaporation and condensation of watery vapor. We have the authority of two of the most able and accurate philosophers, Lavoisier and Laplace, for stating that bodies in passing from the solid or liquid state to that of vapor, and, conversely, in returning from the aeriform condition to the liquid or solid state, give unequivocal signs of either positive or negative electricity,” and he adds, in a footnote:

“M. Pouillet has lately published a set of experiments, which seems to overturn Volta’s theory of the evolution of electricity by evaporation. He has shown that no electricity is evolved by evaporation unless some chemical combination takes place at the same time ...” (Thomson, “Outlines,” p. 440) ... “But we shall be slow to reject the results of experiments performed by such experimenters as Lavoisier and Laplace, especially when confirmed by the testimony of Volta and Saussure.”

With regard to the origin of meteorites, Laplace has advanced the very bold theory that they may be products of Lunar volcanoes, and Prof. Lockhart Muirhead stated that he would “present the reasoning upon which this extraordinary hypothesis is founded in the popular and perspicuous language of Dr. Hutton, of Woolwich: the respect due to the name of Laplace justifying the length of the extract,” which he gives at pp. 633–635, Vol. XIV of the 1857 “Britannica.”

References.—Humboldt, “Cosmos,” London, 1849, Vol. I. pp. 108–109; Young, “Course of Lectures,” London, 1807, Vol. II. p. 501, alluding to “Zach. Mon. Corr.,” VI. p. 276, also to Gilbert, XIII. p. 353, 108, and stating that Olbers had suggested Laplace’s idea in 1795. See “Mem. of the Astronom. Soc. of London,” Vol. III. p. 395: Laplace, “Mem. de l’Institut” for 1809, p. 332; Dr. Young’s “Course of Lectures,” 1807, Vol. I. pp. 249, 250, 522; Vol. II. p. 466; Humboldt, “Cosmos,” London, 1849, Vol. I. pp. 28, 76, 130; Vol. II. p. 712; Lavoisier at A.D. 1781: Biot at A.D. 1803; Annal. de Ch. et Phys., Vol. XV. pp. 72, 73, and for Laplace and Lavoisier, see Delaunay, “Manuel ...” 1809, p. 178; “Mem. de l’Acad. des Sc.,” for 1781; “Journal des Savants,” for Feb. 1850 and Nov. 1887; Houzeau et Lancaster, “Bibl. Gén.,” Vol. II. p. 184; “Cat. Sc. Pap. Roy. Soc.,” Vol. III. pp. 845–848; Johnson’s “Cyclopædia,” pp. 1647–1650 and the “First Supplement,” p. 62.

For Laplace and Joseph Louis Lagrange, see “Mémoires de l’Institut,” Vol. III. p. 22; also “Pioneers of Science,” by Sir Oliver Lodge, London, 1905, Lecture XI, and for Lagrange, consult “Journal des Savants,” Sept. 1844, May 1869, August 1878, Sept. 1879, Sept. 1888 and Oct. 1892.

M. Cyrille Pierre Théodore Laplace, captain in the French navy, is the author of the “Voyage Autour du Monde ... sur la Corvette Favorite ...” and of “Campagne de Circumnavigation de la Frégate l’Artémise ...” published in Paris during the years 1833, 1839 and 1841.

Baron Jean Baptiste Fourier, celebrated French physicist (1768–1830) who, in 1827, succeeded Laplace as head of the Council of the Ecole Polytechnique (“Biog. Gén.,” Vol. XVIII. p. 346) says of his predecessor:

“Posterity, which has so many particulars to forget, will little care whether Laplace was for a short time minister of a great state. The eternal truths which he has discovered, the immutable laws of the stability of the world, are of importance, and not the rank which he occupied” (C. R. Weld, “Hist. Roy. Soc.,” Vol. II. p. 465). Fourier is the author of “Expériences thermo-électriques” (“Encycl. Brit.,” ninth ed., Vol. IX. p. 490; “Eng. Cycl.,” Biography, Vol. II. p. 977).

A.D. 1820.—Dutrochet (René Joachim Henri) (1776–1847) a distinguished French natural philosopher, and likewise medical adviser to the King of Spain, Joseph Bonaparte, publishes an interesting treatise on meteors, in conjunction with Mr. Nathaniel Bowditch, who had already written many very able papers on astronomical subjects and who afterwards translated the “Mécanique Céleste” of Laplace. Eight years later (1828) appeared Dutrochet’s “Nouvelles Recherches ...” wherein he attributes to electricity the direction taken by fluids through animal and vegetable membranes. The passage of a fluid from without inwardly he called endosmosis, and the passage of the fluid from within outwardly he termed exosmosis.

Of Dutrochet, Dr. John Hutton Balfour, of Edinburgh, makes mention when treating of the temperature of plants. He thus expresses himself: “While the nutritive processes are going on in the plant, there is a certain amount of heat produced. This, however, is speedily carried away by evaporation and other causes, and it is not easily rendered evident. Dutrochet, by means of Becquerel’s thermo-electric needle, showed an evolution of heat in plants. In doing this, he prevented evaporation by putting the plant in a moist atmosphere. In these circumstances the temperature of the active vegetating parts, the roots, the leaves, and the young shoots, indicated a temperature above the air of ½ to ¾ of a degree Fahrenheit. Van Beek and Bergsma, in their experiments on the Hyacinthus Orientalis and the Entelea Arborescens, found the proper heat of the active parts of plants about 1·8° F. above that of the air. The vital or proper heat of plants, according to Dutrochet, is found chiefly in the green plants, and it undergoes a quotidian paroxysm, reaching the maximum during the day, and the minimum during the night. When stems become hard and ligneous, they lose this vital heat. Large green cotyledons gave indications of a proper heat. The hour of quotidian maximum varied from 10 a. m. to 3 p. m. in different plants.”

It is stated by Becquerel that in the act of vegetation, the earth acquires continually an excess of positive electricity, while the bark and part of the wood receive an excess of negative electricity. The leaves act like the green part of the parenchyma of the bark—that is to say, the sap which circulates in their tissues is negative with relation to the wood, to the pith, and to the earth, and positive with regard to the cambium. The electric effects observed in vegetables are due to chemico-vital action, and he asserts that the opposite electric states of vegetables and of the earth give reason to think that, from the enormous vegetation in certain parts of the globe, they must exert some influence on the electric phenomena of the atmosphere.

References.—Gmelin’s “Chemistry,” Vol. I. p. 447; “Biog. Gén.,” Vol. XV. p. 506; Poggendorff, “Annalen,” Vol. I. p. 663; Larousse, “Dict. Univ.,” Vol. VI. p. 1448; J. W. Ritter, in “Denkschr. d. Münch. Acad.” for 1814, and the eighth ed. of the “Ency. Brit.” Vol. XXI. p. 635, for observations concerning the mimosa pudica and the mimosa sensitiva; “Cat. Sc. Papers Roy. Soc.,” Vol. II. pp. 422–425; Vol. VI. p. 646; Vol. VII. p. 584; Poggendorff, Vol. I. p. 633; “Observations on the diurnal variation of the magnetic needle,” in Sturgeon’s “Annals,” Vol. VII. pp. 369–370, and in the Comptes Rendus, Vol. XII. p. 298, of Feb. 8, 1841; Burnet, “On the motion of sap in plants. Researches of Dutrochet on Endosmose and Exosmose ...” London, 1829 (“Phil. Mag. or Annals,” Vol. V. p. 389).

A.D. 1820.—Fresnel (Augustin Jean) (1788–1827), one of the most distinguished French mathematicians and natural philosophers, communicates a paper detailing his experiments for decomposing water by means of a magnet. He produced a current in an electro-magnetic helix enclosing a bar-magnet covered with silk, and on plunging the ends of the wire in water he observed some very remarkable effects which are set forth in the Annales de Chimie et de Phys., series 2, Vol. XV. p. 219.

References.—“Eloge de Fresnel,” by Arago, in his “Œuvres,” Vol. I; Account of Fresnel’s life in the “Biog. Univ.;” Whewell, “Hist. of Induc. Sci.,” 1859, Vol. II. pp. 96, 102, 114–117; “Œuvres complètes d’Augustin Fresnel, publiées par les soins du Ministre de l’Instruction Publique,” Paris, 1870, in three vols.

A.D. 1820.—Sir Richard Phillips (1778–1851), communicates, July 11, to the Philosophical Magazine (Vol. LVI. pp. 195–200) a very interesting paper entitled “Electricity and Galvanism Explained on the Mechanical Theory of Matter and Motion.” After reviewing the then existing theories, he concludes by saying:

“Electricity is no exception to the mechanical principles of matter and motion, and in regard to the kindred phenomena of galvanism, I will content myself with observing that it is merely accelerated electricity, the interposing fluid being palpably decomposed and evolving the electrical powers, each term in the series of plates being a new impulse or power added to the previous one, till the ultimate effect is accelerated, like that of a body falling by the continuous impulses of the earth’s motions, or like a nail heated red-hot by accelerations of atomic motion produced by repeated percussions of a hammer.”

Consult “Bibl. Ital.,” Vol. XXVII. p. 107 for references to the “Annals of Philosophy,” in which he mentions an experiment upon a young poplar, “whereby it would seem that copper was imbibed in the branches, etc., from a solution placed at its roots, and that it was precipitated on a knife used to cut off a branch.”

A.D. 1820.—Brewster (Sir David) (1781–1868), a very distinguished English natural philosopher and writer, who had just founded the “Edinburgh Philosophical Journal” in conjunction with Prof. Robert Jameson, announces his discovery of the existence of two poles of greatest cold on opposite sides of the northern pole of the earth. By this he was, like other authors, led to the belief that there might be some connection between the magnetic poles and those of maximum cold, and he remarks (Noad “Manual,” London, 1859, p. 545, and article “Magnetism” in “Encycl. Brit.”): “Imperfect as the analogy is between the isothermal and magnetic centres, it is yet too important to be passed over without notice. Their local coincidence is sufficiently remarkable, and it would be to overstep the limits of philosophical caution to maintain that they have no other connection but that of accidental locality; and if we had as many measures of the mean temperature as we have of the variation of the needle, we might determine whether the isothermal poles were fixed or movable.” Similar opinions entertained by Dr. Dalton, Dr. Traill and Mr. Christie are also mentioned by Noad, who quotes from Oersted’s treatise on “Thermo-Electricity” the statement of the Danish philosopher “that the most efficacious excitation of electricity upon the earth appears to be produced by the sun, causing daily evaporation, deoxidation and heat, all of which excite electrical currents.”

From his able paper in the Edinburgh Philosophical Transactions for 1820, one is led to share Sir David Brewster’s belief “that two meridians of greatest heat and two of greatest cold are called into play, and that the magnetism of our globe depends in great measure upon electro or rather thermo-magnetic currents.” The electro-magnetic hypothesis was, he says, ably supported by Prof. Barlow in his paper “On the probable electric origin of all the phenomena of terrestrial magnetism,” communicated to the Phil. Trans. for 1831. Brewster thus locates the two poles of maximum cold: The American pole in N. Lat. 73, and W. Long. 100 from Greenwich, a little to the East of Cape Walker; the Asiatic pole in N. Lat. 73 and E. Long. 80, between Siberia and Cape Matzol, on the Gulf of Oby. Hence the two warm meridians will be in W. Long. 10 and E. Long. 170, and the two cold meridians in W. Long. 100 and E. Long. 80.

As has already been indicated (under A.D. 1717, Leméry), Sir David Brewster was the discoverer of the pyro-electrical condition of the diamond, the garnet, the amethyst, etc. His development of some of Haüy’s experiments led to a similar discovery, attaching to several mineral salts as well as to the plates and powders of the tourmaline, of the scolezite and the melozite; and he likewise experimented with the boracite, mesotype and with the several minerals and artificial crystals detailed at pp. 208–215, Vol. I of the Edin. Jour. of Science, London, 1826; and in Chap. II. s. 1, vol. viii of the eighth “Encycl. Brit.,” article on “Electricity.”

At Part I. chap. i. s. 6 of the last-named article will be found Brewster’s observations on the nature and origin of electrical light, his latest researches having been made, like those of Joseph von Fraunhofer (see A.D. 1814–1815), on the dark and on the luminous lines which appear in the spectrum formed from it by a prism.

During the year 1831 appeared Brewster’s “Treatise on Optics,” his “Life of Sir Isaac Newton,” and his “Letters on Natural Magic.” It is in one of the chapters of the last-named work that he treats of automatic talking machines and remarks: “We have no doubt that before another century is completed a talking and a singing machine will be numbered among the conquests of science.”

Brewster’s other scientific treatises are too numerous and cover too wide a range to be enumerated here. The “Catal. of Sci. Papers of the Roy. Soc.” (Vol. I. pp. 612–623) gives the titles of as many as 299 contributions made by him on important subjects, and he has had no less than 76 papers in the first 39 parts of the North British Review, 30 in the Phil. Trans. and 28 in the Edin. Review. They appear, in fact, in all the prominent publications of his time, and have won for him leading honours, more especially from the Edinburgh and Aberdeen Universities and the Scotch, Irish, English and French Societies, the French Academy of Sciences doing him the signal honour of selecting him as one of its eight foreign associates in place of Berzelius, deceased. Conjointly with Davy, Herschel and Charles Babbage, he originated the British Association during 1831, and it was in this same year that he was knighted and decorated by King William IV. He had been made a Fellow of the Royal Society of Edinburgh in 1808, and had during the same year undertaken the editorship of the “Edinburgh Encyclopædia of Sci., Lit. and Art.” This he continued for twenty-two years, after which he edited the Edin. Jour. of Sci., and also entered with Taylor and Phillips upon the editorship of the London and Edin. Phil. Mag. and Journal. Many of our readers will doubtless be glad to know that the last named was a continuation of the well-known Philosophical Magazine so often quoted in this “Bibliographical History.”

References.—The obituary notice contributed by Dr. J. H. Gladstone to the proceedings of the Royal Society; Chemical News, Amer. reprint, Vol. II. pp. 198, 233; also p. 293 for accounts given by Sir J. Simpson and Prof. Fraser; J. Robison and Brewster, “A System of Mechan. Phil.,” London and Edin., 1822; Ferguson and Brewster’s “Essays and Treatises on Astr. Elect.,” etc., Edinburgh, 1823; Brewster’s several articles in the “Encycl. Britannica,” 7th and 8th editions, on “Electricity and Magnetism”; Transactions of the Roy. Soc. of Edinburgh, Vols. IX. 1821; XX. Part IV; Edin. Jour. of Sci., Oct. 1824, No. 2, p. 213; Noad, “Manual,” London, 1859, pp. 31, 32, 636–638; Harris, “Magnetism,” Part III. p. 119; Whewell, “Hist. of Induc. Sci.,” 1859, Vol. II. pp. 75, 81, 331, 332; the lectures delivered by Wm. A. Miller during 1867 before the Royal Institution of Great Britain.

Charles Babbage (1792–1871), a prominent English scientist who is mentioned above and who besides being one of the founders of the Royal Astronomical Society, as has already been stated, was also a founder of the British Association and the originator of the Statistical Society, is the author of valuable papers, exhibiting a wide range of learning and research—mainly on mathematical subjects and relating to magnetical and electrical phenomena—which have been published in the Reports of the Royal and other Societies (“English Cycl.,” Vol. I. p. 457; “Encyl. Brit.,” ninth ed., Vol. III. p. 178; Larousse, “Dict.,” Vol. II. pp. 5–6; account of Babbage’s work in C. R. Weld’s “Hist. Roy. Soc.,” Vol. II. pp. 369–391).

A.D. 1820.—Fisher (George) (1794–1873), who two years before had joined Captain David Buchan in his voyage to the Arctic regions, is the first to point out the true cause of the sudden alteration in the rates of chronometers at sea. “He observed,” says Dr. Roget, “that the chronometers on board the ‘Dorothea’ and ‘Trent’ had a different rate of going from that they had on shore, even when these vessels had been frozen in, and therefore when their motion could not have contributed to that variation; ... this effect could be attributed only to the magnetic action exerted by the iron in the ships upon the inner rim of the balance of the chronometers, which is made of steel. A similar influence was perceptible on placing magnets in the neighbourhood of the chronometers. This conclusion was confirmed by experiments made for this purpose by Mr. Barlow, who ascertained that masses of iron devoid of all permanent magnetism occasioned an alteration in the rates of chronometers placed in different positions in their vicinity.”

References.—Fisher’s article “On the Errors in Longitude as Determined by Chronometers at Sea, Arising from the Action of the Iron in the Ships upon the Chronometers,” communicated by John Barrow, F.R.S., to the Phil. Mag., Vol. LVII. pp. 249–257. See besides, Edinburgh Jour. Sci., London, 1826, Vol. V. p. 224; Phil. Trans. for 1820, Part. II. p. 196, and the volume for 1833, relative to magnetical experiments; also the “Lib. U. K.” (Magn.), p. 63. For Capt. Buchan, consult Barrow’s “Chronological History of Voyages into the Arctic Regions.”

Mr. George Thomas Fischer (1722–1848) is the author of “A Practical Treatise on Medical Electricity” (Poggendorff, Vol. I. p. 756).

A.D. 1820.—Bonnycastle (Charles), Professor of Mathematics in the University of Virginia, treats of the distribution of the magnetic fluids in masses of iron, as well as of the deviations which they produce in compasses placed within their influence, at pp. 446–456, Vol. LV of Tilloch’s Philosophical Magazine.

He refers to the then recent publication of Peter Barlow’s “Essay on Magnetic Attractions,” containing the results of many experiments, made principally upon spheres of iron, as well as to Dr. Young’s views of the subject, which were printed by order of the Board of Longitude, and he says that the principle upon which he intends establishing his inquiry “is an extension of the law that regulates the action of electrified bodies upon conductors; which was first given by M. Poisson in the Memoirs of the Institute for 1811, and employed by him to determine the development of the electric fluids in spheres that mutually act on each other.”

The afore-named dissertation, at the time, called forth a rejoinder from a correspondent and a further communication from Mr. Bonnycastle, both of which appear at pp. 346–350, Vol. LVI of the same publication.

References.—Silliman’s Journal, Vol. XL. p. 32; “Sketch of the Life of Chas. Bonnycastle,” by Thomas Thomson; Poggendorff, Vol. I. pp. 234, 235; article “Magnetism,” p. 9, Vol. XIV of the eighth “Britannica.”

A.D. 1820.—Harris (Wm. Snow), member of the College of Surgeons, and a very distinguished English scientist (1791–1867), proposes to the Board of the Admiralty his system of lightning conductors, of which an account appears at p. 231, Vol. LX of the Phil. Mag., as well as in a separate work published at London during 1822. This is followed by his “Observations on the Effects of Lightning ...” 1823, and by papers relative to the defence of ships and buildings from lightning, which were published, more particularly, in several numbers of the Nautical Magazine, the Phil. Mag., the Annals of Electricity, and in the Proc. Lond. Elec. Soc. for 1842, as well as in his “Record of Phil. Papers,” and under separate heads during many years between 1827 and 1854. One of his biographers remarks:

“His researches have gone far to remove certain popular errors as to what have been called ‘conductors’ and ‘non-conductors’ of electricity, and to show the inutility of the old form of lightning rod in the majority of cases; it being necessary, in place of such rod form, to link into one great chain all the metallic bodies employed in the construction of a building, thus providing a connection with these conductors between the highest parts and the ground, the single conductor, in one highest part, being possibly insufficient to divert the course of the fluid and protect the whole fabric. These general principles have been largely applied to the protection of the ships of the Royal Navy during the last five and twenty years, under his advice and direction; and, laying aside the opinions which had been commonly received, the masts themselves of a ship have all been rendered perfectly conducting by incorporating with the spars capacious plates of copper, whilst all the large metallic masses in the hull have been tied, as it were, into a general conducting chain, communicating with the great conducting channels in the masts, and with the sea. This may be considered as the greatest experiment ever made by any country in the employment of metallic conductors for ships, and the result has been to secure the navy from a destructive agent, and to throw new light upon an interesting department of science” (Whewell, “Hist. of Induc. Sci.,” Vol. II. pp. 199, 200; Phil. Mag. for March 1841; eighth “Encycl. Britannica,” Vols. VIII. pp. 535, 610, 611, and XX. p. 24; “Edin. Review” for Oct. 1844, Vol. LXXX. pp. 444–473).

Harris was the first, says Brewster, who introduced accurate quantitative measures into the investigation of the laws of statical electricity—the unit measure by which quantity is minutely estimated—and also the hydro-electrometer and scale-beam balance by which its intensity and the laws of attractive forces at all distances are demonstrated. Of not less value is the thermo-electrometer, by which the heating effects of given quantities of electricity are measured and rendered comparable with the varying conditions of quantity and intensity. Besides these instruments, we owe to Harris the discovery of a new reactive force, through which repulsion and other small physical forces are investigated and determined by means of his bifilar balance, founded upon the reactive force of two vertically suspended parallel threads when twined upon each other at a given angle, and acted upon by a suspended weight. With the aid of these instruments he has carried on a variety of important inquiries into the laws of electrical forces, and the laws and operations of electrical accumulation (eighth “Brit.,” Vol. VIII. p. 535). His papers on the subject appeared in 1825 and 1828, and a résumé of them is given by Noad (“Manual” 1859, pp. 35, 137–140), as well as in the “Electricity” article of the “Britannica,” both of which contain descriptions and illustrations of Harris’ unit jar and electro-thermometer.

During the year 1827 Mr. Harris published in the Trans. Roy. Soc. of Edinburgh his memoir entitled “Experimental Inquiries Concerning the Laws of Magnetic Forces,” which experiments were made by means of a new and very accurate apparatus invented by him for examining the phenomena of induced magnetism. The above was followed by two other memoirs, published in the Phil. Trans. for 1831, “On the Influence of Screens in Arresting the Progress of Magnetic Action ...” and “On the Power of Masses of Iron to Control the Attractive Force of a Magnet,” which are discoursed of in the “Britannica” article on “Magnetism,” wherein special treatment is also given more particularly to Mr. Harris’ researches concerning artificial magnets as well as the magnetic charge, the development of magnetism by rotation and the phenomena of periodical variations (“Rudim. Mag.,” Part III. p. 60; Fahie’s “Hist, of Elec. Tel.,” pp. 283, 284).

Besides additional apparatus named in the subjoined references Mr. Harris invented a very effective steering compass, of which an account is given in Part III. pp. 148–153, of his “Rudimentary Magnetism,” as well as at p. 594 of Noad’s “Manual,” at p. 105 of the “English Cyclopædia” (Arts and Sciences), Vol. III, and at p. 80, Vol. VIII, 1857, “Encycl. Britannica,” and he has also devised a magnetometer for the measurement of electric forces, of which the description and illustrations appear in the last-named publication as transcribed from Mr. Harris’ work already mentioned.

Mr. Harris was made a F. R. S. in 1831, and received the Copley medal four years later. It was in 1843 he published his well-known work “On the Nature of Thunderstorms,” the plans he advocated being adopted in 1847, when he received the order of knighthood as well as a large money grant from the English Government in acknowledgment of his scientific services. The following appears in the obituary notice of Sir Wm. Snow Harris, contributed by Mr. Charles Tomlinson to the Proceedings of the Roy. Soc. (XVI, 1868):

“Harris’ sympathies were with the Bennetts, the Cavendishes, the Singers, the Voltas of a past age. Frictional electricity was his forte and the source of his triumphs. He was bewildered and dazzled by the electrical development of the present day, and almost shut his eyes to it. He was attached too closely and exclusively to the old school of science to recognize the broad and sweeping advance of the new. He was not conscious even of being behind his age when he presented to the Royal Society in 1861 an elaborate paper on an improved form of Bennett’s discharger, and still less in 1864, when he discussed the laws of electrical distribution, and yet relied upon the Leyden jar and the unit jar.”

References.—Trans. of the Plymouth Institution, also Trans. of the Roy. Soc. for 1834, 1836, 1839; “Eng. Encycl.” (“Common Electricity”), Vol. III. p. 801; W. A. Miller, “Elem. of Chem.,” 1864, p. 32. For descriptions of his bifilar balance see the eighth “Britannica,” Vol. VIII. p. 623; Harris, “Rud. Elec.,” p. 99, and “Rud. Magn.,” pp. 119, 120; Noad, “Manual,” pp. 26, 27, 37, 40, 41, 63, 580; C. Stahelin, “Die Lehre ...” 1852; P. Volpicelli, “Ricerche analitiche ...” Roma, 1865, while, for his balance electroscope and electrometers, see “Edin. Phil. Trans.,” Dec. 1831; eighth “Britannica,” Vol. VIII. pp. 540, 590, 620 622, 624; Harris, “Rud. Elec.,” pp. 99, etc.; the “Bakerian Lecture”; the “Report of British Association,” Dundee, 1867, for an able account of electrometers by Sir William Thomson. His electrical machine is described at pp. 74–76 of Noad’s “Manual,” as well as at p. 604, Vol. VIII of the 8th “Britannica,” the latter also giving, at p. 550, Harris’ experiments on the electrical attraction of spheres and planes. “Catal. Sc. Papers Roy. Soc.,” Vol. III. pp. 191–192; Lippincott’s “Biog. Dict.,” 1886, p. 1230; Biography in Harris’ “Frictional Electricity”; “Abstracts of Papers ... Phil. Trans., 1800–1830,” Vol. II. p. 298; Lumière Electrique for Oct. 3, 1891, p. 49; reprint of Sir Wm. Thomson’s “Mathematical Papers,” 1872; “Brit. Asso. Reports” for 1832, 1835, 1836; Edin. Phil. Trans. for 1834; Fahie’s “History,” p. 321; Edin. and London and Edin. Phil. Mag. for 1840; Phil. Trans., 1842; Phil. Mag. for 1856–1857, and Harris’ “Manuals of Electricity, Galvanism and Magnetism,” published in John Weale’s Rudimentary Series.

A.D. 1820.—Mitscherlich (Eilardt—Eilhert), Professor of Chemistry at the Berlin University, discovers what is called Isomorphism (isos, equal; morphe, form), showing that bodies containing very different electro-positive elements could not well be distinguished from each other; it was impossible therefore to put them in distant portions of the classification, and thus, remarks Whewell, the first system of Berzelius crumbled to pieces.

In other words, Mitscherlich was the first to draw attention to the fact that two bodies having the same composition could assume different forms; to this law Berzelius gave the name of Isomerism (isos, equal; meros, part).

Sir John Herschel makes particular mention (“Treatise on Light,” s. 1, 113) of Mitscherlich’s remarkable experiment with sulphate of lime—the alteration in the tints of which by heat, it is said, was first observed by Fresnel. This experiment was repeated by Sir David Brewster, and he discovered still more curious properties in glauberite, all of which are detailed in Vol. I. p. 417 of the London and Edinburgh Phil. Mag. for Dec. 1832.

References.—“Cat. Sci. Papers Roy. Soc.,” Vol. IV. pp. 413–416; “Library Useful Knowledge” (Pol. of Light), p. 63; Poggendorff, Vol. II. pp. 160, 161; the very able treatise of Mr. J. Beete Jukes on “Mineralogical Science”; also Poggendorff’s Annalen, Vol. XV. p. 630, for Mitscherlich on the chemical origin of iron glance in volcanic masses.

A.D. 1820.—Ampère (André Marie) (1775–1836), one of the most distinguished philosophers of the century, Professor of Mathematical Analysis in the French Ecole Polytechnique (1809), afterwards Professor of Physics at the Collège de France, reads before the Académie Royale des Sciences, Sept. 18, 25, Oct. 9, 13, and Nov. 6, 1820, papers containing a complete exposition of the phenomena of electro-dynamics. His investigations were subsequently embodied in the “Recueil d’Observations ...” Paris, 1822, and were still further developed during 1824 and 1826, as shown through both his “Précis de la théorie ...” and “Théorie des Phénomènes Electro-Dynamiques.”

The news of Oersted’s discovery of the relation existing between the electric current and the magnet—the fundamental fact of electro-magnetism—was made known in July 1820, and the inquiry was at once taken up more particularly by Ampère, Arago, Biot, and Félix Savary in France, as well as by Berzelius, Davy, De la Rive, Cumming, Faraday, Joseph Henry, Schweigger, Seebeck, Sturgeon, Nobili and others throughout Europe and elsewhere. Of all these scientists, Ampère proved the most energetic, and, within three months of the announcement of Oersted’s discovery, his first memoir on the subject was publicly read in Paris.

In this first paper, Sept. 18, he explains the law determining the position of the magnetic needle in relation to the electric current, and he also makes known his intended experiments with spiral or helical wires, which he predicts will acquire and retain the properties of magnets so long as the electrical current flows through them. He likewise explains his theory of magnets, saying that if we assume a magnet to consist of an assemblage of minute currents of electricity whirling all with the same direction of rotation around the steel molecules and in planes at right angles to the axis of the bar, we will have an hypothesis which will account for all the known properties of a magnet. He constructed his spirals and helices, and to the astonishment of all, he produced magnets formed only of spools of copper wire traversed by electric currents. We can readily imagine, adds Prof. A. M. Mayer, the intense interest awakened by this discovery, a discovery which caused Arago to exclaim, “What would Newton, Halley, Dufay, Æpinus, Franklin and Coulomb have said if one had told them that the day would come when a navigator would be able to lay the course of his vessel without a magnetic needle and solely by means of electric currents?” “The vast field of physical science,” says Arago, “perhaps never presented so brilliant a discovery, conceived, verified and completed with such rapidity.” Thus Ampère became the author of a beautiful generalization, which not only included the phenomena exhibited by the new combinations of Oersted, but also disclosed forces existing in arrangements already familiar, although they were never detected till it was thus pointed out how they were to be looked for. His electro-dynamic theory of the action of currents and of magnets has been thought worthy of a place near the Principia of Newton ... it deservedly gained for him the title of the Newton of electro-dynamics, as he did for this branch of science even more than Coulomb had previously done for electro-statics (Profs. A. M. Mayer and W. B. Rogers, “Memorial of Jos. Henry,” 1880, pp. 81, 476; Lardner, “Lectures,” 1859, Vol. II. p. 120; Fahie, “Hist. Tel.,” p. 276).

The experiments of Oersted and Ampère were at once greatly extended by many scientists, among whom may be especially mentioned MM. Yelin, Bœckmann, Van Beek, De la Rive, Moll, Nobili, Barlow and Cumming. The last named apparently gave the earliest notice of the increased effects of a convolution of wire around the magnetic needle, and constructed the first astatic needle galvanometer (Trans. Camb. Soc., Vol. I. p. 279). The Chevalier Julius Konrad Yelin (1771–1826), German mathematician, ascertained that the electricity of an ordinary machine when passed along a helix, either in simple electrical sparks or by discharges from a battery, has the effect of rendering an included needle magnetic. According to Dr. Henry, M. Bœckmann found in varying these experiments that no modification of the effect is produced by altering the diameter of the helix from half an inch to thirteen inches. With a helix of thirty-four inches diameter, and a coated surface of 300 square inches, much less magnetism was, however, imparted; and with one of eighty-four inches it was scarcely perceptible. It was found that a needle outside of the helix was magnetized as much as one within; that after being once fully magnetized a continuation of the discharges diminished its power; and that five jars, each of 300 square inches, did not produce, by repeated discharges, much more effect than one of them (Poggendorff, Vol. II. p. 1382; Gilbert’s Annalen for 1820–1823).

In his second paper, Sept. 25 (Ann. de Chim. et de Phys., Vol. XV. pp. 59–170), Ampère makes known the results of his experiments on the mutual attractions and repulsions of electrical currents, showing conclusively that when the voltaic current is passed in the same direction through two parallel wires, so placed as to move freely, they attract each other, and that they are repelled if the currents are passed in opposite directions. Thus he establishes the second fundamental law of electro-magnetism, the first law, instituted as we have seen by Oersted, being that the magnetical effect of the electrical current is a circular motion around the current. In the last-named paper he also proposes the hypothesis of currents of electricity circulating from east to west around the terrestrial globe in planes at right angles to the direction of the dipping needle, to account for the phenomena of terrestrial magnetism (Roget, “Electro-Magn.,” p. 47).

In his third paper, Oct. 9, Ampère investigates the properties of currents transmitted through wires forming closed curves (courbes fermées) or complete geometrical figures, an inquiry also alluded to in another memoir read Oct. 30, 1820.

These papers were immediately followed by others, which engaged nearly all the sittings of the Academy between Dec. 4, 1820, and Jan. 15, 1821. In these he brings forth new confirmations of his theories, and reduces the phenomena of electro-magnetism to mathematical analysis.

Mr. Samuel Prime remarks (“Life of Morse,” 1875, p. 266) that the discovery of the action of the spiral coil upon the magnetic needle seems to have been independently made by Ampère in 1821:

“I showed that the current which is in the pile acts on the magnetic needle by the conjunctive wire. I described the instrument, which I proposed to construct, and, among others, the galvanic spiral. I read a note upon the electro-chemical effects of a spiral of iron wire, subjected to the action of the earth, directing an electric current as well as a magnet. I announced the new fact of the attraction and repulsion of two electric currents, without the intermediation of any magnet, a fact which I had observed in conductors twisted spirally (Tilloch’s Journal of Science, Vol. LVII. p. 47, 1821).

One of his biographers, Professor Chrystal says: “Scarcely had the news of Oersted’s discovery reached France, when a French philosopher, Ampère, set to work to develop the important consequences which it involved. Physicists had long been looking for the connection between magnetism and electricity, and had, perhaps, inclined to the view that electricity was somehow to be explained as a magnetic phenomenon. It was, in fact, under the influence of such ideas, that Oersted was led to his discovery. Ampère showed that the explanation was to be found in an opposite direction. He discovered the ponderomotive action of one electric current on another, and, by a series of well-chosen experiments, he established the elementary laws of electro-dynamic action, starting from which, by a brilliant train of mathematical analysis, he not only evolved the complete explanation of all the electro-magnetic phenomena observed before him, but predicted many hitherto unknown. The results of his researches may be summarized in the statement that an electric current, in a linear circuit of any form, is equivalent in its action, whether on magnets or other circuits, to a magnetic shell bounded by the circuit, whose strength at every point is constant and proportional to the strength of the current. By his beautiful theory of molecular currents, he gave a theoretical explanation of that connection between electricity and magnetism which had been the dream of previous investigators. If we except the discovery of the laws of the induction of electric currents, made about ten years later by Faraday, no advance in the science of electricity can compare for completeness and brilliancy with the work of Ampère. Our admiration is equally great, whether we contemplate the clearness and power of his mathematical investigations, the aptness and skill of his experiments, or the wonderful rapidity with which he elucidated his discovery when he had once found the clew.”

“Oersted,” remarks M. Babinet, “was the Christopher Columbus of magnetism; Ampère became its Pizarro and its Fernand Cortez.”

Of Ampère’s astatic needles, a description, taken from one of his memoirs (Ann. de Ch. et de Ph., Vol. XVIII. p. 320), appears at pp. 280–281 of Fahie’s “History” (Knight’s “Mech. Dict.,” 1874, Vol. I. p. 171, and Vol. II. p. 1181). For this greatly perfected form of galvanometer the credit has erroneously been given to Prof. Cumming, who first suggested the idea of neutralizing the directive force of the needle arising from the earth’s magnetism, which he did by placing a magnetized needle immediately beneath the movable or index needle. Fahie adds, in a footnote: “In Prof. Cumming’s paper ‘On the Connection of Galvanism and Magnetism,’ read before the Cambridge Philosophical Society, April 2, 1821, he described a near approach to the astatic needle. In order to neutralize the terrestrial magnetism he placed a small magnetized needle under the galvanometer needle” (Trans. Cam. Phil. Soc., Vol. I. p. 279). The credit of Ampère’s discovery is sometimes given to Nobili, as in Noad’s “Manual of Electricity,” London, 1859, p. 327; also Roget’s “Electro-Magnetism” in “Library of Useful Knowledge,” London, 1832, p. 42.

As has been already shown (Laplace, A.D. 1820), the first proposal to apply Oersted’s discovery to telegraphic purposes by substituting the deflection of the magnetic needle through electric currents for the divergence of the pith balls of the electroscope, was made by Ampère, in his Memoir of Oct. 2, 1820, which appears in the Comptes Rendus, and at p. 72, Vol. XV of the Annales de Chimie et de Physique. His plan, remarks Sabine, was, however, doomed to the same fate as that of Sömmering, of never coming into practice, and for the same reasons, principally the number of line wires. Had Ampère combined his system, or rather the one of Laplace, with that which Schweigger proposed of reducing Sömmering’s telegraph to two wires, or with any other using a code of signals, the problem of the electric telegraph would have been solved from the year 1820. Ampère makes no mention of surrounding the needles with coils of wire, as is so frequently stated by writers on the telegraph. Indeed he could not then have even heard of the galvanometer; for, although Schweigger’s paper on the subject was read at Halle on the 16th of September 1820, it was not published until the November following.

M. Jean Jacques Antoine Ampère (1800–1864), son of André Marie Ampère, was an accomplished scholar who succeeded François Andrieux as professor at the Collège de France and became a member of the French Academy in 1847.

References.—For accounts of Ampère’s rotary magnet, electro-dynamic cylinders, revolving battery, and of his electripeter employed to alter rapidly the direction of the electric current in voltaic batteries, consult pp. 639, 640, 643, Vol. VIII of the eighth “Britannica.” Fahie, “Hist. of El. Tel.,” p. 303. See “Catal. Sci. Papers Roy. Soc.,” Vol. I. pp. 58, 61; Messrs. Sainte-Beuve et Littré’s account of his life and labours in the Revue des Deux Mondes for Feb. 15, 1837; “Notice sur M. Ampère,” par M. E. Littré, Paris, 1843; Arago’s “Eulogy on Ampère,” translated, at pp. 111–171 of the “Report of the Smithsonian Institution” for 1872. Consult also “Report Smiths. Instit.” for 1857, pp. 100–107; Ampère’s biography in the Sci. Am. Suppl., No. 674, p. 10760; also Ampère’s “Journal et Correspondance,” Poggendorff, Vol. I. pp. 39, 40; Address of His Royal Highness the Duke of Sussex to the Eng. Roy. Soc., 1836; Barlow on “Magnetic Attractions”: Comptes Rendus for 1838, Vol. VII. p. 81; Bibl. Univ., XX; Phil. Mag., Vols. LVI. p. 308; LVII. pp. 40–47, “On the Electro-Magnetic Experiments of Oersted and Ampère,” by Mr. Hatchett, and pp. 47–49; Ann. de Phys. de Bruxelles, Vol. VII; Ann. de Ch. et de Phys., XXIX; Du Moncel, Vol. III. p. 7; “Acad. de Paris,” Sept. 12, 1825; La Lum. Elect. for Oct. 31, 1891, p. 202; Roch, in “Zeitschr. f. Mathém.” 1859, p. 295; Roget on Ampère’s theory of Mag.; K. W. Knochenhauer, Pogg. Annal., XXXIV. p. 481; J. Marsh, “On a Particular Construction of M. Ampère’s Rotating Cylinder,” Phil. Mag., LIX. p. 433, 1822; Henn, “De Amperi principiis ...”; “Memorial of Joseph Henry,” 1880, pp. 59, 81; “Lib. of Use. Know.” (El. Mag.), pp. 24, 28, 83–92; Harris, “Rud. Elec.,” pp. 170, 171, and “Rud. Mag.,” p. 130; Noad, “Manual,” pp. 661–662, 861–864; “Encycl. Metrop.” (El. Mag.), Vol. IV. pp. 5–8; Highton, “Elec. Teleg.,” p. 39; Gmelin’s “Chemistry,” Vol. I. p. 317; Mrs. Somerville, “Conn. Phys. Sci.,” 1846, pp. 320, 321; Dr. Lardner, “Lectures,” Vol. II. p. 125; J. F. W. Herschel, “Prelim. Dis. Nat. Phil.,” 1855, p. 243; Whewell, “Hist. Induc. Sc.,” 1859, Vol. II. pp. 242, 246, 619; “Ann. of Sc. Disc.” for 1850, p. 129, and for 1865, p. 125; “Smithsonian Report” for 1878, p. 273; Sturgeon, “Sci. Researches,” Bury, 1850, pp. 12, 16, 29; Jour. Frankl. Inst. for 1851, Vol. XXII. p. 59; Turnbull, “El. Mag. Tel.,” 1853, pp. 55 and 221; (Vail’s “History,” pp. 133, 134; Prof. Henry’s Evid., 85a, record; Doct. Channing’s Ev., 47a, record; Hibbard, Ev., 31a. ...) See also Humboldt’s “Cosmos,” articles “Aurora Borealis,” “Volcanoes,” “Earthquakes”; Ampère et Babinet, “Exposé des Nouv. Déc. ... de Oersted, Arago, Ampère, Davy, Biot, Erman, Schweigger, De la Rive,” etc., Paris, 1822, translated into German “Darstellung der neuen ... dem Französischen,” Leipzig, 1822, and alluded to in Lumière Electrique for July 18, 1891, pp. 148, 149; Hachette et Ampère, “Sur les Expériences de Oersted et Ampère”: Journal de Physique for September 1820. Annales de Chimie for 1825; “Journal des Savants,” for June 1872; “Dict. Génér. de Biogr. et d’Histoire,” Paris, 2^e ed., pp. 85–86; “Collection de Mémoires relatifs à la Physique,” Paris 1885, 1887, Vols. II and III passim, as per indexes; “Amer. Journ. of Psychology,” Vol. IV. pp. 6–7.

For William Ritchie (1790–1837), the author of an able paper, “On electro-magnetism, and Ampère’s proposal of telegraphic communication by means of this power,” consult Phil. Trans. for 1833, p. 313; “Abstracts of Papers ... Roy. Soc.,” Vol. II. pp. 350, 382; Phil. Mag. or Annals, Vol. VII, 1830, p. 212; Phil. Mag. and Journal of Science, Vol. III, 1833, pp. 37, 122, 124, 145.

For Leopoldo Nobili (1784–1835), frequently mentioned above, consult “Bibl. Univ.,” Bruxelles, 1834 (Sc. et Arts), Tome LVI. pp. 82–89, 150–168; “Edin. Trans.” Vol. XII and Phil. Mag. Vol. XI, 1832, p. 359, for the account of experiments made by James David Forbes, similar to those of Nobili, wherein an electric spark was elicited from a natural magnet. For J. D. Forbes, see also Phil. Mag., 1832, Vol. XI. p. 359. For Nobili and Antinori, consult Phil. Mag., Vol. XI, 1832, pp. 401, 466; “Bibl. Britan.,” Vol. XXV, 1824, N.S. p. 38; Vol. XXIX, 1825, N.S. p. 119. For Antinori and Marchese Cosimo Ridolfi, consult “Bibl. Britan.” Vol. XVI, N.S., 1821, pp. 72–75, 101–118.

For Prof. James Cumming (1777–1861), also frequently named in above article, consult Phil. Mag., Vol. LX, 1822, p. 253; “Bibl. Britan.,” Vol. XXV, N.S., 1824, p. 104, for experiments of Cumming, Trail and Marsh; the investigations in the same line of Mr. Thos. Stuart being especially reported on in “Bibl. Britan.,” Vol. XXVII, N.S., 1824, pp. 199–206; “Dict. of Nat. Biog.,” Vol XIII. p. 296; “Edin. Phil. Journal,” 1824, Vol. X. p. 185; “Cat. Sc. Papers Roy. Soc.,” Vol. I. pp. 58–61; Vol. VI. p. 565; Vol. VII. p. 29; “Bibl. Britan.,” Vol. XVI, N.S. p. 309; Vol. XVII, N.S. p. 16; Vol. XIX. p. 244; Vol. XX. pp. 173, 258; Vol. XXIV. p. 109.

For Le Chevalier Julius Konrad von Yelin (1771–1826), consult “Bibl. Britan.,” Vol. XXIII, N.S., 1823, p. 38; Vol. XXIV, N.S., 1823, p. 253, and, especially, the important tract on the discovery of thermo-magnetism at p. 31 of his “Die Akademie der Wissenschaften und ihre Gegner,” Munich, 1822.

A.D. 1820.—Arago (Dominique François Jean), famous French astronomer, physicist and statesman (1786–1853), who at the early age of twenty-three had, besides being Assistant Astronomer to the Observatory, become the successor both of Lalande in the Academy of Sciences and of Monge in the chair of analytical mathematics at the Polytechnic School, and who, conjointly with Gay-Lussac, had founded the highly valued Annales de Chimie et de Physique in 1816, communicates to the French Institute, on the 25th of September 1820, his discovery that the electric current has the power of developing magnetism in iron and steel. Into the axis of a galvanic conductor made in the form of a coil, or helix, he placed a needle, the extremities of the wire coil being connected to the poles of a battery, and with this he proved that the wire not only acted on bodies already magnetized, but that it could develop magnetism in such as did not already possess the power. When soft iron was used, the magnetism given was only temporary, but on repeating the experiment, M. Arago succeeded completely in permanently magnetizing small steel needles. Arago’s paper on the subject appears at p. 94, Vol. XV of the Ann. de Ch. et de Ph., and it is said that at about the same time Dr. Thos. J. Seebeck (1770–1831), and Georg Friedrich Pohl (1788–1849) laid similar results before the Berlin Academy, also that Sir Humphry Davy independently made a like discovery, of which he advised Dr. Wollaston, Nov. 12, 1820. Reference to this fact has already been made at Davy, under date A.D. 1801, wherein it was stated that the latter had found iron filings to so adhere to the connecting wire as to form a mass ten or twelve times the thickness of the wire. This was also the case in the experiments of M. Arago, who, upon observing that the filings rose before coming in contact with the conjugate wire, drew the conclusion that each small piece of iron was converted into a temporary magnet. Thus was Arago led to the discovery of what is called magnetic induction by electric currents, or, in other words, that an electrical current passing through a conductor will induce magnetic action in such bodies near it as are capable of being magnetized (Phil. Trans. for 1821, p. 9; Tilloch’s Jour. of Sci., Vol. LVII. p. 42, 1821; eighth “Britannica,” Vol. VIII. p. 532 and Vol. XIV. p. 640; Thomas Thomson, “Outline of the Sciences,” p. 563).

A fact worth noting in connection with the development of Oersted’s discovery by both Arago and Ampère, is that in order “to prevent the communication of the electricity laterally in the folds of the coil, the wire was insulated by varnish in the first instance and afterward by winding silk or cotton around it” (F. C. Bakewell, “Elec. Sci.,” London, 1853, p. 37).

On the 22nd of November 1824, Arago announced to the French Academy of Sciences the remarkable discovery made by him of a new source of magnetism in rotatory motion. He was led to this by observing that when a magnetic needle was oscillating above or close by any body, such as water or a plate of metal, it gradually oscillated in arcs of less and less amplitude, as if it were standing in a resisting medium, and, besides, that the oscillations performed in a given time were the same in number (Humboldt’s “Cosmos,” “Magnetic Observations,” 1825). He caused a circular copper plate to revolve immediately beneath a magnetic needle or magnet, freely suspended so that the latter might rotate in a plane parallel to that of the copper plate, and he found that the needle tends to follow the circumvolution of the plate; that it will deviate from its true direction, and that by increasing the velocity of the plate the deviation will increase till the needle passes the opposite point, when it will continue to revolve, and at last with such rapidity that the eye will be unable to distinguish it. This, says Mrs. Somerville, is quite independent of the motion of the air, since it is the same if a pane of glass be interposed between the magnet and the copper. When the magnet and the plate are at rest, not the smallest effect, attractive, repulsive, or of any kind, can be perceived between them. In describing this phenomenon Arago states that it takes place not only with metals, but with all substances, although the intensity depends upon the kind of substance in motion.

Arago’s experiments were repeated in London, March 7, 1825. His valuable discovery, which obtained for him the Copley medal, and which confirms the doctrine of the universal prevalence of magnetism in all bodies, is recorded in Arago’s “Sur les Déviations ... aiguille aimantée” (An. de Ch. et de Ph., Vol. XXXIII, and Phil. Trans., p. 467 for 1825), and a solution of the phenomena is given by Faraday in Phil. Trans. for 1832, p. 146, by Sir John Leslie in the Fifth Dissertation of the eighth “Britannica,” p. 746, as well as in the article “Magnetism” of the latter publication, and in Mrs. Somerville’s “Conn. of Phys. Sc.,” pp. 325–327. (See also the observations recorded in Humboldt’s “Cosmos,” 1849, Vol. I. pp. 172, 173; in Dr. Thomson’s “Outline of the Sciences,” pp. 556–558; Fahie, pp. 282, 283, 321; Dr. Whewell, Vol. II. pp. 254–256; Brewster’s Edin. Jour. of Sci., 1826, Vol. III. p. 179; “Dict. Gén. de Biogr. et d’Histoire,” Paris, 2^e ed. p. 126.)

In Brewster’s Edinburgh Journal of Science (Vol. V. p. 325), notice is given of Arago’s then recent researches on the influence which bodies considered not magnetic have on the motions of the magnetic needle, and reference is made to a new communication transmitted by Arago to the Académie des Sciences, as well as to a report of additional experiments in the same line given at meetings held July 3 and 10, 1826. Arago satisfactorily meets the denials made by Leopoldo Nobili and another Italian natural philosopher (Liberato Giovanni Bacelli) that substances not metallic have any influence on the magnetic oscillations, and he announces as a result of his investigations that, for certain positions of a vertical needle, and for velocities of rotation sufficiently rapid, the repulsive force which is exerted in the direction of the radius is as great as the force perpendicular to the radius, of which the effects are observed upon a horizontal needle.

Poisson having stated in his memoir “On the Theory of Magnetism” in motion (see Poisson at A.D. 1811) that Coulomb had recognized the magnetic virtue in all bodies, independently of the iron which they contain, Arago remarked that the idea of Coulomb was quite different from his, Coulomb having been of opinion that a quantity of iron, although too small for chemical analysis even to appreciate, was sufficient to produce in bodies which contained it appreciable magnetic effects. MM. Thénard and La Place confirmed this remark. Brewster adds that, in justice to Coulomb, it is necessary to state that he is the undoubted author of the discovery that all bodies, whether organic or inorganic, are sensible to the influence of magnetism. M. Biot has remarked that there are two ways of explaining this, either all substances in nature are susceptible of magnetism, or they all contain portions of iron, or other magnetic metals, which communicate to them this property. This last explanation, though adopted by Coulomb, by no means affects his claim to the discovery of the general fact that all bodies, whether organic or inorganic, are susceptible of becoming magnetic. Prof. Hansteen has drawn from numerous experiments and observations the important conclusion that every vertical object, of whatever material it is composed, has a magnetic south pole above, and a north pole below (Edin. Phil. Journal for January-April 1821).

M. Arago made many valuable investigations concerning the influence of the aurora borealis on the needle, on the variations of the latter, upon the nature of meteors, lightning, the zodiacal light, magnetic storms, etc. etc., which are admirably recorded more particularly in the great work of Alex. von Humboldt. The latter remarks that Arago has left behind him a treasury of magnetical observations (upward of 52,600 in number) carried on from 1818 to 1835, which have been carefully edited by M. Fédor Thoman, and published in the “Œuvres Complètes de François Arago” (Vol. IV. p. 493). Much could be said, especially regarding Arago’s paper, presented by him to the Academy of Sciences in 1811, which is considered to have established the foundation of chromatic polarization. Mention must at any rate be made of the fact that in Humboldt’s estimation the discovery of the two kinds of polarization of light may be considered the most brilliant of the century. They, unquestionably, rank among the most splendid of optical phenomena.

Etienne Louis Malus, a distinguished French philosopher (Fifth Dissert. of “Encycl. Brit.”), discovered in 1808 polarization by reflection from polished surfaces, and Arago, during 1811, made the discovery of coloured polarization. A world of wonder, remarks Humboldt, composed of manifold modified waves of light having new properties was now revealed. A ray of light which reaches our eyes, after traversing millions of miles from the remotest regions of heaven, announces of itself in Arago’s polariscope (consisting of a plate of quartz cut across the axis placed in one end of a tube, at the other end of which is a doubly refracting prism) whether it is reflected or refracted, whether it emanates from a solid or fluid, or gaseous body, even announcing the degree of its intensity (Delambre, “Histoire de l’Astronomie,” p. 652; Humboldt, “Cosmos,” 1849, Vol. I. p. 33; Vol. II. p. 715).

In 1818, Arago was elected a F.R.S.; he became a member of the Royal Astronomical Society and also member of the Bureau des Longitudes during 1822, was made Perpetual Secretary of the Academy and Director of the Paris Observatory eight years later, and received the Rumford medal in 1850. The Copley medal given him in 1825 had never before been conferred upon a Frenchman of science. It was upon his urgent request that the “Annuaire du Bureau des Longitudes” and “Les Comptes Rendus hebdomadaires” were commenced by the Academy, 1828–1835.

In a letter to Schumacher, Humboldt speaks of Arago as “one gifted with the noblest of natures, equally distinguished for intellectual power and for moral excellence.” In conjunction with Gay-Lussac, Arago was, for almost half a century, Humboldt’s most intimate friend, and their ever-increasing intimacy became such as to lead to a perfect unity of thought on scientific subjects. It cannot, therefore, be considered an exaggerated expression of feeling when, in a letter to Geoffroy St. Hilaire, dated Berlin, June 24, 1829, Humboldt should conclude with the words: “Pray remember me to MM. Valenciennes, Deleuze and Cuvier, but especially to him whom I hold dearest in this life, to M. Arago.”

References.—Poggendorff, Vol. I. pp. 53, 54, and the several biographies named at p. 202, Vol. I of “Johnson’s New Univ. Cycl.,” 1877; J. A. Barral, “Œuvres de F. Arago,” 1854–1855; Faria E. De e Arago, “Breve compendio ...” Lisbon, 1800; Arago’s “Notices Scientifiques,” “Cat. Sc. Papers Roy. Soc.,” Vol. I. pp. 80–84; Vol. IV. pp. 697–701; Vol. VI. pp. 567, 736–737; Vol. VIII. p. 537; “Encycl. Metropol.,” Vol IV (Magnetism), pp. 6, 7; J. F. W. Herschel, “Nat. Phil.,” 1855, pp. 117, 244, and his account of the repetition of M. Arago’s experiments on rotatory magnetism in Phil. Trans. for 1825; Whewell, “Hist. Induc. Sci.,” 1859, Vol. II. p. 226; Phil. Mag., Vols. LIX. p. 233; LVII. pp. 40–49; LVIII. p. 50; LXI, p. 134; “Lib. Useful Knowledge’” (Magnetism), p. 91; Noad, “Manual,” pp. 204, 534; “Ann. of Sci. Disc.” for 1850, p. 124; Harris, “Rud. Magn.,” Parts I, II. pp. 58–61 and Phil. Trans. for 1831, Part I; Prime’s “Life of Morse,” pp. 168, 265, 266; Gmelin’s “Chemistry,” Vol. I. p. 317; Comptes Rendus for 1836, Vol. II. p. 212; Dredge, “Electr. Illum.,” Vol. II. p. 122; Sturgeon, “Scient. Res.,” Bury, 1850, pp. 13, 37, 216, etc.; Appleton, “New Am. Cycl.,” Vol. XI. p. 71; Sci. Am. Suppl., No. 204, p. 3254; La Lumière Electrique for Oct. 31, p. 202; “Reports of the Smithsonian Institution” for 1857, pp. 102, 107; for 1862, pp. 132–143, and p. 127 of last named for Malus’ discovery. Houzeau et Lancaster, “Bibl. Générale,” Vol. I. part. i. pp. 676–677 detailing the contents of Arago’s “Œuvres Complètes,” published in thirteen volumes under the direction of J. A. Barral, also Vol. II. p. 76; Cornhill Magazine, Vol. XVII. p. 727; Pierre Prévost, “Tentative,” Genève, 1822 (Poggendorff, Vol. II. p. 525); Phil. Mag., Vol. LVIII. p. 50; Vol. LXI. p. 134; “Abstracts of Papers ... Roy. Soc.,” Vol. II. p. 249.

A.D. 1821.—Ridolfi (Marquis Cosimo di), an Italian agriculturist, is the author of several treatises on fenomeni elettro-magnetici, published in Florence, wherein he expresses the belief that “because electricity produces both magnetic and calorific phenomena, the elements giving these separately may possibly be so compounded together as to produce electricity; which infers that electricity is a compound of magnetism and caloric.”

References.—“Antologia di Firenze,” 1824, p. 159, and “Biblio. Ital.,” Vol. LXIII. p. 268 for Ridolfi’s description of the electric plate machine of Novellucci; also “Annales de Chimie et de Physique,” Vol. X. p. 287; Sturgeon, “Scientific Researches,” 1850, Sec. I. p. 29; “Bibliothèque Universelle” for Feb. 1821.

A.D. 1821.—Scoresby (Dr. William) (1789–1857), English master-mariner, and author of numerous scientific and other treatises, first publishes, in the “Trans. of the Edinburgh Society,” accounts of his magnetometer—magnetimeter—and of his electro-magnetic experiments. These were duly followed up by full reports of his many interesting investigations relative, more particularly, to the development of magnetic properties of metals by percussion, as well as to magnetic induction, and regarding the uniform permeability of all known substances to the magnet’s influence.

References.—“Abstracts of Papers ... Roy. Soc.,” London 1832–1833, Vol. II. pp. 108, 168, 210; “Dict. of Nat. Biog.,” London, 1897, Vol. LI. p. 6; Phil. Trans. for 1822–1824; “Trans. Edin. Soc.,” Vol. IX. pp. 243–258, 353, 465; Vol. XI for 1824; Vol. XII for 1831; Vol. XIII for 1832, and Vol. XIV for 1833; “Brewster’s Jour. of Sc.,” Vol. VIII for 1828; “Bibliothèque Britannique,” Genève, 1796, N.S., Vol. XXIX for 1825, p. 185; “Edin. Phil. Jour.” for 1823, Vol. IX. p. 45.

A.D. 1821.—Babinet (Jacques) (1794–1872), French scientist, is the author of a very valuable treatise, published in Paris, upon the magnetical discoveries of Oersted, Ampère, Arago, Davy and others. This was followed by his “Résumé complet de la physique,” etc., and by a companion work treating of the relations of ponderable and imponderable bodies to the phenomena of magnetism and electricity, also, during the year 1829, by his Memoir upon the determination of terrestrial magnetism.

He succeeded Savary as Professor at the Collège de France in 1838, and, two years later, took the place of Dulong in the section of General Physics at the Académie des Sciences, becoming not long after the Assistant Astronomer at the Paris Observatory for Meteorology.

His numerous scientific treatises are to be found throughout the “Mémoires de la Société Philomathique,” the “Annales de Physique,” the “Comptes Rendus,” the “Revue des Deux-Mondes” and other prominent publications of the day.

References.—Larousse, “Dict. Univ.,” Vol. II. p. 10; “Eng. Cycl.,” London, 1872, Supplement, p. 143; “Biog. Gén.,” Vol. IV. p. 21; Mme. Blavatsky, “Isis Unveiled,” Vol. I. p. 202; and Ronalds’ “Catalogue,” pp. 10–11, for the joint works of Ampère and Babinet.

A.D. 1821.—Pfaff (Christian Heinrich) (1773–1852), who became Professor of Medicine, Physics, etc., at the Kiel University, and was one of the most energetic followers of Volta, sends an unusually interesting communication to Gilbert’s “Annalen der Physik” and to Schweigger’s “Journal für Chemie und Physik,” wherein he very ably supports the views of the Pavia physicist.

Pfaff had, long before that, become favourably known through numerous scientific papers, which were translated into the leading foreign journals, the ones entitled “Dissertatio inauguralis ...” published at Stuttgart, and “Über thierische Elektricität,” published at Leipzig, having brought him special distinction. He had also written, more particularly, upon the experiments made by Alex. von Humboldt as well as relative to Pacchiani’s “Formation of Muriatic Acid by Galvanism,” alluded to at the A.D. 1805 entry, and it was by reason of the investigations made by Pfaff and Van Marum that the use of the voltaic column was generally abandoned. These scientists had constructed very strong piles consisting, in some instances, of as many as seventy large separate discs, when they found that the lower layers of wet cloth or of pasteboard were so seriously compressed by the discs above them as to neutralize their effect.

References.—Johann Samuel T. Gehler’s “Phys. Wörterbuch,” Vol. VI. pp. 507, 517–518; “Roy. Soc. Cat. Sc. Papers,” Vol. IV. pp. 866–871; “Ann. der Chemie,” Vol. XXXIV. p. 307; Vol. LX. p. 314; “Annales de Chimie et de Physique,” Vol. XLI. pp. 236–247; Sturgeon, “Annals,” Vol. VIII. pp. 80, 146; Noad, “Manual,” p. 558; Wilkinson, “Elements,” Vol. I. pp. 1–8, 18, 22, 196, 326, 407; Vol. II. p. 106; “Encycl. Brit.” ninth ed., Vol. XVIII. p. 725; “Soc. Philom.,” Vol. II. p. 181; Phil. Mag., Vol. XXVII. p. 338.

A.D. 1821.—Faraday (Michael), a very distinguished English chemist and natural philosopher (1791–1867), who probably did more for the development of the study of electrical science than any other investigator, publishes his “History of the Progress of Electro-Magnetism” and succeeds, on the morning of Christmas (December 25), 1821, both in causing a magnetic needle to rotate round a wire carrying an electric current and in making the wire rotate around the needle, thus rendering possible the production of continuous mechanical motion by electricity.

The apparatus with which he produced this result is described in nearly all works treating of natural philosophy. Premising his reference to this discovery of Mr. Faraday, whose original papers thereon appear in the Quarterly Journal of Sciences and the Arts, Vol. XII. pp. 75, 186, 283 and 416 (the first bearing date September 11, 1821), Dr. Whewell says that on attempting to analyze the electro-magnetic phenomena observed by Oersted and others into their simplest forms, they appeared, at least at first sight, to be different from any mechanical actions which had yet been observed. It seemed as if the conducting wire exerted on the pole of the magnet a force which was not attractive or repulsive, but transverse; not tending to draw the point acted on nearer, or to push it further off, in the line which reached from the acting point, but urging it to move at right angles to this line. The forces appeared to be such as Kepler had dreamt of in the infancy of mechanical conceptions, rather than such as those of which Newton had established the presence in the solar system, and such as he, and all his successors, had supposed to be the only kinds of force which exist in nature. The north pole of the needle moved as if it were impelled by a vortex revolving round the wire in one direction, while the south pole seemed to be driven by an opposite vortex (called by Wollaston vertiginous magnetism and considered by Mr. Barlow as the result of tangential action). The case seemed novel, and almost paradoxical. It was soon established by experiments, made in a great variety of forms, that the mechanical action was really of this transverse kind. And a curious result was obtained, which a little while before would have been considered as altogether incredible: that this force would cause a constant and rapid revolution of either of the bodies about the other—of the conducting wire about the magnet, or of the magnet about the conducting wire (Vol. XII of the “Journal of the Royal Institution”; Watkins, “Popular Sketch of Electro-Magnetism; or Electro-Dynamics,” London, 1828; Mrs. Somerville, “Connection of Phys. Sciences,” 1846, p. 315).

Passing over many of Faraday’s important scientific investigations in other lines, we come to his second great discovery, that of magneto-electric induction, which is the converse of Oersted’s (developed by Ampère and Arago), the production of electricity by magnetism. This is recorded in the first series of “Experimental Researches in Electricity,” read November 24, 1831 before the Royal Society, of which body Faraday had become a Fellow during 1824, and it is published at p. 125 of the Phil. Trans. for 1832.

It appears that upon observing certain phenomena, which he described as Volta-electric, he concluded before long that magnetism in motion ought to produce an electric current just as electricity was made to imitate all the effects of magnetism. He carried on many experiments, and after the announcements made by Arago to the French Academy, November 22, 1824, he endeavoured to make the conducting wire of the voltaic circuit excite electricity in a neighbouring wire by induction, just as the conductor charged with common electricity would have done, but he obtained no satisfactory results until August 29, 1831 (Annales de Chimie, Vol. XLVIII. p. 402). He remarks: “Certain effects of the induction of electrical currents have already been recognized and described; as those of magnetism; Ampère’s experiments of bringing a copper disc near to a flat spiral; his repetition, with electro-magnets, of Arago’s extraordinary experiments, and perhaps a few others. Still it appeared unlikely that these could be all the effects which induction by currents could produce.... These considerations, with their consequence, the hope of obtaining electricity from ordinary magnetism, have stimulated me at various times to investigate experimentally the inductive effects of electric currents. I lately arrived at positive results, and not only had my hopes fulfilled, but obtained a theory which appeared to me to open out a full explanation of Arago’s magnetic phenomena, and also to discover a new state which may probably have great influence in some of the most important effects of electric currents.” His very important conclusion was finally verified, October 1–17, in the following manner. He had taken a helix, or spool of copper wire, which latter, Prof. Brande tells us, was covered with silk as in his former experiments and which was connected by its extremities with a galvanometer, the deflection of which would of course announce a current of electricity in the spiral and wires connected with it, and he found that while in the act of introducing the pole of a powerful bar-magnet within the coils of the spiral, a deflection of the galvanometer took place in one direction, and that when in the act of withdrawing, it took place in the opposite direction; so that each time the conducting wire cut the magnetic curves, a current of electricity was, for the moment, produced in it. Dr. Whewell’s account of the discovery is so well interspersed with references that it deserves repetition here:

“In 1831, Faraday again sought for electro-dynamical induction, and, after some futile trials, at last found it in a form different from that in which he had looked for it. It was then seen, that at the precise time of making or breaking the contact which closed the galvanic circuit, a momentary effect was induced in a neighbouring wire, but disappeared instantly (Phil Trans., 1832, p. 127, 1st ser., Art. 10). Once in possession of this fact, Mr. Faraday ran rapidly up the ladder of discovery, to the general point of view. Instead of suddenly making or breaking the contact of the inducing circuit, a similar effect was produced by removing the inducible wire nearer to or further from the circuit (Art. 18)—the effects were increased by the proximity of soft iron (Art. 28)—when the soft iron was affected by an ordinary magnet, instead of the voltaic wire, the same effect still recurred (Art. 37)—and thus it appeared, that by making and breaking magnetic contact, a momentary electric current was produced. It was produced also by moving the magnet (Art. 39)—or by moving the wire with reference to the magnet (Art. 53). Finally, it was found that the earth might supply the place of a magnet in this as in other experiments (2nd ser., Phil. Trans., p. 163) and the mere motion of a wire, under proper circumstances, produced in it, it appeared, a momentary electric current (Art. 141). These facts were curiously confirmed by the results in special cases. They explained Arago’s experiments: for the momentary effect became permanent by the revolution of the plate. And without using the magnet, a revolving plate became an electrical machine (Art. 150), a revolving globe exhibited electro-magnetic action (Art. 164), the circuit being complete in the globe itself without the addition of any wire; and a mere motion of the wire of a galvanometer produced an electro-dynamic effect upon its needle (Art. 171).... And thus he was enabled, at the end of his second series of ‘Researches’ (December 1831), to give, in general terms, the law of nature to which may be referred the extraordinary number of new and curious experiments which he has stated (Arts. 256–264), namely, that if a wire move so as to cut a magnetic curve, a power is called into action which tends to urge a magnetic current through the wire; and that if a mass move so that its parts do not move in the same direction across the magnetic curves, and with the same angular velocity, electrical currents are called into play in the mass. And here might properly be added the experimental distinction between a helix and a magnet, which Faraday subsequently pointed out (‘Exper. Res.,’ Art. 3273): ‘Whereas an unchangeable magnet can never raise up a piece of soft iron to a state more than equal to its own, as measured by the moving wire, a helix carrying a current can develop in an iron core magnetic lines of force of a hundred or more times as much power as that possessed by itself when measured by the same means.’”

An article on the reduction of Mr. Faraday’s discoveries in magneto-electric induction to a general law appeared in the “Philosophical Transactions of the Royal Society” Vol. III. p. 37, and at Vol. IV. p. 11, new series, of the Philosophical Magazine (see Faraday’s first two Memoirs in the Phil. Trans., Book XIII. chaps. v and viii; letter to Gay-Lussac in Annales de Chimie, Vol. LI. 1832, pp. 404–434; Phil. Mag., Vol. XVII. pp. 281, 356); while, in the Phil. Trans. for 1832, p. 132, is the Report of his production of the electric spark through a modified arrangement in which the electric current was induced by an electro-magnet, as shown in his subsequent work published in London during 1834. This is alluded to in Vol. V. pp. 349–354 of the Phil. Mag. for latter year, and in Poggendorff’s Annalen, Vol. XXXIV. pp. 292–301 for 1835. (See also Bakewell, “Elect. Science,” pp. 39, 140, 144.)

“Around the magnet, Faraday

Is sure that Volta’s lightnings play;

But how to draw them from the wire?

He took a lesson from the heart

’Tis when we meet—’tis when we part,

Breaks forth the electric fire.”

Herbert Mayo, in Blackwood.

In Prof. Alfred M. Mayer’s address, delivered before the American Association at Boston, August 26, 1880, we read: “It is not generally known or appreciated that Henry and Faraday independently discovered the means of producing the electric current and the electric spark from a magnet. Tyndall, in speaking of this great discovery of Faraday, says: ‘I cannot help thinking while I dwell upon them, that this discovery of magneto-electricity is the greatest experimental result ever obtained by an investigator. It is the Mont Blanc of Faraday’s own achievements. He always worked at great elevations, but higher than this he never subsequently attained.’ And it is this same physicist who further remarks (‘Johnson’s Cycl.,’ Vol. II. pp. 26–27) that all our induction coils, our medical machines, and the electric light so far as it has been applied to lighthouses, are the direct progeny of Faraday’s discovery. In the paper here referred to (Nov. 24, 1831) he for the first time calls the ‘magnetic curves,’ formed when iron-filings are strewn around a magnet, ‘lines of magnetic force.’ All his subsequent researches upon magnetism were made with reference to those lines. They enabled him to play like a magician with the magnetic force, guiding him securely through mazes of phenomena which would have been perfectly bewildering without their aid. The spark of the extra current, which I believe was noticed for the first time by Prof. Joseph Henry, had been noticed independently by Mr. William Jenkin. Faraday at once brought this observation under the yoke of his discovery, proving that the augmented spark was the product of a secondary current evoked by the reaction of the primary upon its own wire.” The phenomenon of the spark from the extra current here alluded to was first announced by Henry in July 1832. He had observed that when the poles of a battery are united by means of a short wire of low resistance, no spark or at least a very faint one is produced, but when the poles of the battery are connected by a long copper wire and mercury cups, a brilliant spark is obtained at the moment the circuit is broken by raising one end of the wire out of its cup of mercury and also that the longer the wire and the greater the number of its helical convolutions, the more powerful would be the effect (Silliman, “Am. Jour. of Sc.,” Vol. XXII). The results of Faraday’s investigation of the extra current first appeared in the Phil. Mag. for November 1834.

The references already named give an account of many other important results attained by Faraday during 1831 and up to the date of the publication of the third series of his “Experimental Researches” (p. 76), wherein he recognizes the “Identity of Electricities derived from different sources”[60] (Vol. I. par. 265 and 360), after investigating the electricities of the machine, the pile, and of the electrical fishes, and after employing as conductors the entire plant of the metallic gas pipes and water pipes of the city of London (Phil. Trans. for 1833, p. 23; Poggendorff, Annalen, Vol. XXIX, 1833, pp. 274, 365).

In the fourth series, relating to “A New law of electric conduction” (Vol. I. par. 380, 381, 394, 410), he demonstrates the influence of what is called “the state of aggregation” upon the transmission of the current. He found that although the latter was conveyed through water it did not pass through ice. This he subsequently explained by saying that the liquid condition enables the molecule of water to turn round so as to place itself in the proper line of polarization, which the rigidity of ice prevents. This polar arrangement must precede decomposition, and decomposition is an accompaniment of conduction (Phil. Trans. for 1833, p. 507; Poggendorff, Annalen, Vol. XXXI, 1834, p. 225; also Phil. Mag., Vol. X. p. 98; “Royal Inst. Proc.,” Vol. II. p. 123; Silliman’s Journal, Vol. XXI. p. 368).

Other series (pars. 309, 450, 453–454, 472, 477, 661–662, 669, etc.) treat of “Electro-chemical or electrolytic decomposition.” The experiments of Wollaston in this line have been given under the A.D. 1801 date, where Prof. Faraday’s opinion of them is also expressed. Faraday was successful in the employment of Wollaston’s apparatus for the decomposition of water, and he afterwards devised an arrangement enabling him to effect true electro-chemical decompositions by common electricity as well as by the voltaic pile. For this, it is said, he used an electric battery consisting of fifteen jars and a plate machine having two sets of rubbers and a glass disc fifty inches in diameter, the whole presenting a surface of 1422 inches. One revolution of the plate could be made to give ten or twelve sparks, each one inch long, while the conductors afforded sparks ten to fourteen inches in length. He also devised a discharging train, to instantaneously carry off electricity of the feeblest tension by connecting a thick wire as he had previously done with the London gas and water pipes. A good description of the methods by which he succeeded with the latter apparatus in establishing the analogy between ordinary and voltaic electricity is given in the eighth “Britannica,” Vol. VIII. pp. 596–597. He had shown, at paragraph 371 and p. 105 of his “Researches,” that as a measure of quantity, a voltaic group of two small wires of platinum and zinc, placed near each other, and immersed in dilute acid for three seconds, yields as much electricity as the electrical battery, charged by thirty turns of a large machine; a fact that was established both by its momentary electro-magnetic effect, and by the amount of its chemical action, but, in order to enable him to establish a principle of definite measurement, he devised a voltameter or volta-electrometer as mentioned at paragraph No. 739 (Noad, “Manual,” p. 365). By means of this apparatus he calculated that a single grain of water in a voltaic cell will require for its decomposition a quantity of electricity equal to that liberated in 800,000 discharges of the great Leyden battery of the Royal Institution (“Researches,” par. 861). Also, that the decomposition of a single grain of water by four grains of zinc in the active cell of the voltaic circle, produces as great an amount of polarization and decomposition in the cell of decomposition, as 950,000 charges of a large Leyden battery, of several square feet of coated surface; an enormous quantity of power, equal to a most destructive thunderstorm. Tyndall remarks (“Notes on Electricity,” No. 118, also “Faraday as a Discoverer,” 1868, p. 44) that Weber and Kohlrausch ascertained that the quantity of electricity associated with one milligramme of hydrogen in water, if diffused over a cloud 1000 metres above the earth, would exert, upon an equal quantity of the opposite electricity at the earth’s surface, an attractive force of 2,268,000 kilogrammes.[61]

Faraday introduced new terms to express more specifically the circumstances attending electro-chemical decomposition. Objections had long been made to the designation poles—one positive, the other negative—on the ground that such did not convey a correct idea of the effects produced. These designations had been given under erroneous supposition that the poles exerted an attractive and repulsive energy towards the elements of the decomposing liquid, much as the poles of the magnet act towards iron. When connecting the extremities of a battery, the electricity simply makes a circuit; the current passes through the substance to be decomposed and the elements remain in operation until the connection is broken. Since the poles merely act as a path to the current he calls them electrodes (electron, electricity, odos, a way); that part of the surface of the decomposing matter which the current enters—immediately touching the positive pole—he designates as anode (ana, upward) and the part of the matter which the current leaves—next to the negative pole—cathode (kata, downward). He names electrolyte (luo, to set free) the fluid decomposed directly by electricity passing through it; the term electrolyzed meaning electro-chemically decomposed. The elements of an electrolyte are named ions (ion, going), the anion being the body (in sulphate of copper solution, the acid) which goes up to the positive pole, to the anode of the decomposing body, whilst the cation is that (in sulphate of copper solution, the metal) which goes down to the negative pole, to the cathode of the decomposing body.

The many tests which he made with his voltameter led him to the conclusion “that under every variety of circumstance, the decompositions of the voltaic current are as definite in their character as those chemical combinations which gave birth to the atomic theory” (Phil. Trans. for 1833, p. 675; for 1834, p. 77; Poggendorff, Annalen, Vols. XXXII. p. 401; XXXIII. pp. 301, 433, 481; Bakewell, “Electric Science,” p. 124; “Brit. Assoc. Report” for 1833, p. 393; Henry’s “Memoirs of Dalton,” p. 106).

The eighth series of his “Researches” (Vol. I. pars. 875, etc.) treats of the “electricity of the voltaic pile,” a further investigation of which is shown through the papers constituting his sixteenth and seventeenth series as per Index of Vol. II. p. 302. Faraday establishes by very simple experiments the most powerful known refutation of Volta’s contact theory and shows conclusively that the current in the pile results from the mutual chemical action of its elements, just as Fabbroni and Wollaston had stated before him. An extract from the conclusion of his very elaborate defence of the chemical theory reads as follows: “... the contact theory assumes, that a force which is able to overcome powerful resistance ... can arise out of nothing: that, without any change in the acting matter, or the consumption of any generating force, a current can be produced, which shall go on for ever against a constant resistance, or only be stopped as in the voltaic trough, by the ruins which its exertion has heaped upon its own course.... The chemical theory sets out with a power, the existence of which is pre-proved, and then follows its variations, rarely assuming anything which is not supported by some corresponding simple chemical fact. The contact theory sets out with an assumption to which it adds others, as the cases require, until at last the contact force, instead of being the firm unchangeable thing at first supposed by Volta, is as variable as chemical force itself. Were it otherwise than it is, and were the contact theory true, the equality of cause and effect must be denied. Then would perpetual motion also be true; and it would not be at all difficult, upon the first given case of an electric current by contact alone, to produce an electro-magnetic arrangement, which, as to its principle, would go on producing mechanical effects for ever” (“Exp. Res.,” pars. 2071–2073, Vol. II. pp. 103–104; Phil. Trans. for 1834, p. 425; for 1840, pp. 61, 93; Poggendorff, Annalen, Vols. XXXV. pp. 1, 222; LII. pp. 149, 547; LIII. pp. 316, 479, 548. Auguste Arthur De la Rive, “Archives de l’Elect.,” Genève, 1841–1845, Vol. I. pp. 93, 342; Graham, “Elem. of Chem.,” London, 1850, Vol. I. pp. 242, etc.; Faraday and Sturgeon, “Ann. of Elec.,” Vol. IV. pp. 229, 231; Daniell, “Intro. to Study of Chem. Phil.”; Liebig, Annal., Vol. XXXVI. p. 137; Figuier, “Expos. et Hist.,” 1857, Vol. IV. p. 434. Also De la Rive’s “Treatise,” Vol. I. pp. 393–402; “Exper. Researches,” Vol. I. pp. 322–323—induction of galvanic current upon itself).

Faraday’s theory of induction offers nothing new as to the nature of the electric forces—it simply indicates the manner of their distribution and the laws by which they are affected. His experiments show that electrization by influence is possible only by means of continuous particles of air or other non-conducting medium (dielectric), that no electric action occurs at a distance greater than the interval existing between two adjacent molecules of such medium, in which latter a true polarization of the particles takes place, and that it is by means of this polarization that electric force is transferred to a distance. Induction only takes place through insulators: induction is insulation, it being the action of a charged body upon insulating matter, of which latter the particles communicate to each other in a very minute degree the electric forces whereby they become polarized and are enabled to transmit an equal amount of the opposite force to a distance. The latter property is termed inductive force or specific inductive capacity, and Faraday discovered that the intensity of electric induction varies in different insulating media; for instance, the induction through shell-lac (the first substance he experimented with) being twice as great as through a like thickness of air. It was while experimenting with shell-lac that he first observed the singular phenomenon of the return or residual charge, i. e. the charge which would of itself gradually reappear in the apparatus after the latter had been suddenly and perfectly discharged. This, he considered due to the penetration, into the substance of the dielectric, of a portion of the charge by conduction. The inductive capacity of all gases he found to be the same as that of air, and this property does not alter with variations in their density.

His discovery of the specific inductive capacity of various substances has been already alluded to (A.D. 1772, Cavendish). Faraday’s biographer in the ninth “Britannica” says: “It appears, from hitherto unpublished papers, that Henry Cavendish had, before 1773, not only discovered that glass, wax, rosin and shell-lac have higher specific inductive capacities than air but had actually determined the numerical ratios of these capacities. This, of course, was not known to Faraday or other electricians of his time.” It was on the 30th of November, 1837, Faraday communicated to the Royal Society the paper on Induction wherein he announces the re-discovery of specific inductive capacity. One of its most important results to-day, remarks John Tyndall, “is the establishment of the specific inductive capacity of insulators—a subject of supreme importance in connection with submarine cables. As a striking illustration of Faraday’s insight, it may be mentioned that as early as 1838 he had virtually foreseen and predicted the retardation produced by the inductive action between the wires of submarine cables and the surrounding sea-water” (Tyndall’s “Notes on Electricity,” 1871, pp. 160–161; “Exper. Researches,” Index Vol. I.; “Faraday as a Discoverer,” new edition, p. 89). Consult, also, the references entered at Cavendish, A.D. 1772; J. E. H. Gordon, “Phys. Treatise on Elect. ...” London, 1883, Vol. I. chap. xi. par. 81–83, which alludes to “Exper. Researches,” 1161, Vol. I. p. 360 as well as to the investigations of specific inductive capacities made by Boltzmann, Romich and Fajdiga, Romich and Nomak, Schiller, Silow, Wüllner, Dr. Hopkinson, J. E. H. Gordon, Ayrton and Perry, and gives the “General Table of Specific Inductive Capacities,” detailing the observations of Cavendish, Faraday and all the others named above. See, besides, “Reprint of Papers ...” Sir Wm. Thomson, 1872 to 1884, 2nd ed., paragraphs 36, 46, 50; Phil. Trans., 1838, pp. 1, 79, 83, 125; 1842, p. 170; Poggendorff, Annalen, Vols. XLVI. pp. 1, 537; XLVII. pp. 33, 271, 529; XLVIII. pp. 269, 424, 513; XCVI. p. 488; XCVII. p. 415; Phil. Mag., Vols. IX. p. 61; XI. p. 10; XIII. pp. 281, 355, 412; “Bibl. Univ.,” Vol. XVII. p. 178 and “Archives des Sc. Phys.,” Vol. XXXI. p. 48; “Journal de Pharm.,” Vol. XXVII. p. 60; W. S. Harris, “Specific Inductive Capacities ...” (Phil. Trans., 1842).

In the fifteenth series of his “Exper. Researches” (Vol. II. pars. 1749–1795), Faraday gives the results of his experiments proving the identity of the power of the gymnotus or the torpedo with common electricity. He concludes that “a single medium discharge of the fish is at least equal to the electricity of a Leyden battery of fifteen jars, containing 3500 square inches of glass coated on both sides, charged to its highest degree” (p. 8); “all the water and all the conducting matter around the fish, through which a discharge circuit can in any way be completed, is filled at the moment with circulating electric power and this state might be easily represented generally in a diagram by drawing the lines of inductive action upon it. In the case of a gymnotus surrounded equally in all directions by water, these would resemble generally in disposition the magnetic curves of a magnet having the same straight or curved shape as the animal, that is, provided he in such cases employed, as may be expected, his four electric organs at once” (p. 12) (C. Matteucci, “Traité des phénom. ...” Paris, 1844, pp. 188–192).

Then follow in due course, Faraday’s remarkable papers relating to the magnetization of light and the illumination of magnetic lines of force, the polar and other condition of diamagnetic bodies, etc. These communications, which he made to the Royal Society in November and December 1845, contain the particulars of what many consider to be his most brilliant discoveries. He first shows that when a ray of polarized light passes through a piece of silicated borate of lead glass placed between the poles of a natural (or preferably an electro-) magnet, so that the line of magnetic force shall pass through its length, the polarized ray will experience a rotation. The law is thus expressed: “If a magnetic line of force be going from a North pole or coming from a South pole, along the path of a polarized ray, coming to the observer, it will rotate that ray to the right hand, or if such a line of force be coming from a North pole or going from a South pole it will rotate such a ray to the left hand” (Phil. Trans. for 1846 and 1856; Poggendorff, Annalen, Vol. C. pp. 111, 439; Noad, “Manual,” pp. 804–805; Harris, “Rud. Mag.,” Parts I and II. p. 71; Whewell, “Hist. of the Inductive Sciences,” Vol. II. pp. III, 133; Gmelin’s “Chemistry,” Vol. I. pp. 168–169). At the Faraday Centenary Celebration held in London, June 18, 1891, Lord Rayleigh observed that “the full significance of the last-named discovery was not yet realized. A large step towards realizing it, however, was contained in the observation of Sir William Thomson, that the rotation of the plane of polarization proved that something in the nature of rotation must be going on within the medium when subjected to the magnetizing force, but the precise nature of the rotation was a matter for further speculation, and perhaps might not be known for some time to come.”

Through Faraday’s other communication, is made known the discovery of diamagnetism. Therein he shows, as the result of his customary careful experimental explorations that the magnetism of every known substance (even tissues of the human frame) is manifested in one of two ways. Either the body is, like iron, attracted by the magnet, taking a position coincident with the magnetic forces which he calls paramagnetic (para beside or near, magnetes, magnes, magnet) or bodies—like bismuth, for instance—are repelled by the poles and should therefore be called diamagnetic (dia, across) for they set themselves across, equatorially, or at right angles to the magnetic lines. As far back as 1788, the repulsion by bismuth was first observed by Brugmans, while M. Becquerel, during 1827, confirmed the observation, said to have been made by Coulomb, that a needle of wood could be made to point across the magnetic curves, and stated that he had found such a needle place itself parallel to the wires of a galvanometer. Yet, neither M. Becquerel nor M. Lebaillif, who (after Saigy and Seebeck) had called attention to the repulsion of both bismuth and antimony by the magnet, made a distinction of the diamagnetic force from the paramagnetic as Faraday did. Amongst other results, this English scientist found that phosphorus is at the head of all diamagnetic substances, bismuth taking the lead amongst the metals, whilst, of many gases and vapours, oxygen proved to be the least diamagnetic, in fact, the only one which is paramagnetic (“Lond., Edin., and Dub. Phil. Mag.” for December 1850). All the facts set forth in Mr. Faraday’s paper are, according to Brande, resolvable by induction into the general law; that while every particle of a magnetic body is attracted, every particle of a diamagnetic body is repelled by either pole of a magnet: these forces continue as long as the magnetic power is sustained, and cease on the cessation of that power, standing therefore in the same general antithetical relation to each other as the positive and negative conditions of electricity, the northern and southern polarities of ordinary magnetism, or the lines of electric and magnetic force in magneto-electricity. (Phil. Trans. for 1846–1851; Phil. Mag., Vols. XXVIII. pp. 294, 396, 455; XXIX. pp. 153, 249; XXXVI. p. 88; Annales de Chimie, Vol. XVII. p. 359; Poggendorff, Annalen, Vols. LXVIII. p. 105; LXX. p. 283; LXXXII. pp. 75, 232; “Bibl. Univ. Archives,” Vols. I. p. 385; III. p. 338; XVI. p. 89; Ludwig F. von Froriep, “Notizen,” Vols. XXXVII. cols. 6–8; XXXIX. col. 257; Erdmann, “Jour. Prak. Chem.,” Vol. XXXVIII. p. 256; Liebig, Annal., Vol. LVII. p. 261; Napoli, “Rendiconto,” Vol. VI. p. 227; Silliman’s “Journal,” Vols. II. p. 233; X. p. 188; Walker, “Elect. Mag.,” Vol. II. p. 259; John Tyndall, “Researches on Diamagnetism and Magne-crystallic Action,” London, 1870, pp. 1, 38, 89, 90, 137; Whewell, “Hist. of Ind. Sc.,” 1859, Vol. II. p. 620; “Athenæum” for January 31, 1846; Plücker’s paper “On the relation of Magnetism and Diamagnetism,” dated September 8, 1847, in Poggendorff’s Annalen and in Taylor’s “Scientific Memoirs,” Vol. V. part ix. p. 376; Edmond Becquerel’s “Memoir on Diamagnetism” in An. de Ch. et de Ph., Vol. XXXII. p. 112; “Practical Mech. and Engin. Mag.,” 1846, p. 117; for “Coexistence of Paramagnetism and Diamagnetism in same Crystal,” see “Jour. of Chem. Soc.,” London, February 1906, p. 69, taken from Les Comptes Rendus).

During the course of Faraday’s experiments to ascertain the effects of magnetism on crystals some very curious results were obtained with bismuth. Having suspended four bars of the metal horizontally between the poles of the electro-magnet, the first pointed axially; the second equatorially; another equatorial in one position, and obliquely equatorial if turned round on its axis fifty or sixty degrees; the fourth equatorially and axially under the same treatment; whilst all of them were repelled by a single magnetic pole, thus showing their strong and well-marked diamagnetic character. These variations were attributed to the regularly crystalline condition of the bars. He then chose carefully selected crystals and, after describing their peculiar action between the poles, he says that “the results are altogether very different from those produced by diamagnetic action. They are equally distinct from those dependent on ordinary magnetic action. They are also distinct from those discovered and described by Plücker, in his beautiful researches into the relation of the optic axis to magnetic action; for there the force is equatorial, whereas here it is axial. So they appear to present to us a new force, or a new form of force in the molecules of matter, which, for convenience’ sake, I will conventionally designate by a new word, as the magne-crystallic force.” Prof. A. M. Mayer justly observes (“Johnson’s Cycl.,” I. 1342) that the above-named facts “received their full explanation at the hands of Tyndall, whose subtile examination or lucid explanation of these phenomena—though not popularly known—we think form his greatest claim to illustrious distinction as a man of science.” For an extract from the last-named work relative to M. Poisson’s remarkable theoretic prediction of magne-crystallic action, see the article concerning that scientist at A.D. 1811. (Consult Phil. Trans. for 1849, pp. 4, 22; Phil. Mag., Vol. XXIV. p. 77 and s. 4, Vol. II. p. 178; De la Rive, “Treatise,” Vol. I. pp. 482–497; “Athenæum,” No. 1103, p. 1266; Gmelin’s “Chemistry,” Vol. I. pp. 514–519.)

The remarkable discoveries we have named were succeeded by many others of a very high order, the references to which occupy as many as 158 separate entries through pp. 555–560, Vol. II. of the “Catal. of Sci. Papers of the Royal Society.” Among those may be singled out his additional investigations regarding the magnetism of gases and the magnetic relations of flames and gases, the lines of magnetic force, subterraneous electro-telegraphic wires (Phil. Mag. s. 4, Vol. VII. 1854), the relation of gravity to electricity, atmospheric magnetism, likewise his recorded observations on hydro-electricity, magneto-electric light for lighthouses, pyro-electricity, the electrophorus, Wheatstone’s telegraph, etc. (“Roy. Inst. Proc.” for 1854–1858, pp. 555–560). It was in 1848 he wrote of the powerful insulating properties of gutta-percha (Gmelin’s “Chemistry,” Vol. I. p. 313; “Lond. and Edin. Phil. Mag.,” Vol. XXXII. p. 165), and he not long after constructed a very singular apparatus to a Leyden jar consisting of a wire 140 miles long, perfectly insulated with gutta-percha, one end of which communicated with an insulated pile of 360 elements of zinc and copper charged with acidulated water, as described in the “Britannica.” The results of his inquiries concerning the Leyden jar charge of buried electric conducting wires were, according to Whitehouse’s pamphlet on the Atl. Tel. (p. 5) communicated to the Roy. Inst. during the year 1854.

The life of Michael Faraday is an admirable example of extraordinary successes achieved through patient endeavour and constancy of purpose over unusual obstacles of birth and education. M. Dumas, in the sixteenth volume of the London “Chemical News,” tells us he was the only man in England who raised himself to the first rank in science, whose every attribute can be fearlessly held up as a model. He had none of the “ambition, eternal pining after rank or hauteur” of Davy, nor “the secretiveness and coldness” of Wollaston. “Faraday’s intellect, while it burnt as brightly as Davy’s, was as deep searching as Wollaston’s, and as reverent as Newton’s, yet it had nothing in it which could repel us, chill us, or forbid our affection.” The son of a blacksmith, he was first placed in a bookseller’s shop, then apprenticed to a bookbinder, but his tastes were averse to the trade and he was led to seek instruction in another line, more particularly after attending the evening lectures of Mr. Tatum, yet, as already stated (see Dr. George Gregory, A.D. 1796), it was while in M. Riebau’s (the bookbinder’s) employ that chance threw in his way the works which led him to enter the channels in which he subsequently became so distinguished. To a friend, he writes:

“Your subject interested me deeply every way; for Mrs. Marcet was a good friend to me, as she must have been to many of the human race. I entered the shop of a bookseller and bookbinder at the age of thirteen, in the year 1804, remaining there eight years, and during the chief part of the time bound books. Now it was in those books, in the hours after work, that I found the beginning of my philosophy. There were two that especially helped me, the ‘Encyclopædia Britannica,’ from which I gained my first notions of electricity, and Mrs. Marcet’s ‘Conversations on Chemistry,’ which gave me my foundation in that science. Do not suppose that I was a very deep thinker, or was marked as a precocious person ... but facts were important to me and saved me. I could trust a fact and always cross-examined an assertion. So when I questioned Mrs. Marcet’s book by such little experiments as I could find means to perform, and found it true to the facts as I could understand them, I felt that I had got hold of an anchor in chemical knowledge, and clung fast to it....” (“Faraday as a Discoverer,” by John Tyndall, 1868, pp. 6–7).

Think of the startling, not to say marvellous, achievements growing out of Faraday’s subsequent first experiments with an electrical machine made out of an old bottle and by the aid of a Leyden jar constructed with a medicine phial!

In 1812, he was taken by Mr. Dance to the lectures of Sir Humphry Davy, whose chemical assistant he became the following year and in whose company, as we have already seen (A.D. 1801), he travelled on the Continent until 1815. Mr. Davies Gilbert, to whom is due Davy’s introduction to the Royal Institution, has said of the last-named illustrious philosopher that the greatest of all his discoveries was the discovery of Faraday. In 1816, Michael Faraday was placed by Mr. Brande in charge of the “Quarterly Journal of Science,” and, during 1823, he was elected corresponding Member of the French Academy, becoming F.R.S. the ensuing year through the influence of his friend Richard Phillips. It was during 1825–1826 he published in the Phil. Trans. the chemical papers wherein he announces the discovery of benzole (called by him bicarburet of hydrogen) to which, says Hoffmann, “we virtually owe our supply of aniline, with all its magnificent progeny of colours.” In 1827, Faraday succeeded Davy as lecturer at the Royal Institution, and, from 1829 to 1842, he occupied the post of chemical lecturer at the Royal Military Academy, Woolwich. The “Experimental Researches,” to which we have so often alluded, first appeared in the 1831 Phil. Trans., and were afterwards collected in three volumes, which were published respectively during 1839, 1844, 1855. Faraday was made D.C.L. in 1832 by Oxford University, and, one year later, he received the Fullerian professorship of chemistry in the Royal Institution, which he held till his death. A pension was given him by the English Government in 1835, and he also received the Royal Medal, which latter was again conferred upon him, together with the Rumford Medal, during 1846. Ten years before (1836) he had become a member of the Senate of the London University, and during the year 1858 the Queen allotted him the residence in Hampton Court where he died in 1867. “Taking him for all in all,” says Tyndall, “it will, I think, be conceded that Faraday was the greatest experimental philosopher that the world has ever seen; and I would hazard the opinion that the progress of future research will tend not to diminish but to enhance the labours of this mighty explorer.”

References.—“Life of Faraday,” by Dr. H. Bence Jones (Sec. R.I.); “Michael Faraday,” by Dr. J. H. Gladstone, 1872; “Faraday as a Discoverer,” by John Tyndall; the biographical sketch by Prof. Joseph Lovering; “Michael Faraday, his Life and Work,” by Silv. P. Thompson, New York, 1898; “The Chemical News” (Am. Rep.), Vol. I. pp. 246, 250, 276, and Vol. II. pp. 98, 202; Report of the Faraday Centenary celebration at the London Roy. Inst., June 17, 1891; Poggendorff, Vol. I. pp. 719–722; Larousse, “Dict. Univ.,” 1872, Vol. VIII. p. 99; “Biog. Gén.,” Vol. XVII. pp. 90–93; “Men of the Time,” London, 1856; Reports on Faraday’s Lectures delivered before the Roy. Inst. (taken from the “London Mining Journal,” Nos. 714, 717–722), at pp. 319–324, 387–393; Vol. XVIII for 1849 of “Jour. of Frankl. Inst.”; Gmelin’s “Chemistry,” Vol. I. pp. 424, etc., 435–436, 514–519; Poggendorff, Annalen, Vols. LXXXVIII. p. 557; Ergänz, Vol. I. pp. 1, 28, 64, 73, 108, 187, 481–545; Gustav Wiedemann, “Die Lehre von Galv.,” 1863 and “Die Lehre von der Elektricität,” 1883; W. H. Uhland, “Die Elektrische Licht,” 1884, p. 62; An. Sc. Dis. for 1850, pp. 129, 131, 132; for 1851, p. 133, and for 1852, p. 110 on “Atmospheric Magnetism,” taken from “Jameson’s Journal,” July 1851; for 1853, p. 132; for 1856, p. 161; for 1858, p. 177, Faraday, “On the Conservatism of Force”; for 1860, p. 125, Faraday on “Static Induction”; for 1863, p. 108, “Elec. Lamp in Lighthouses”; for 1868, p. 169; for 1870, p. 10; for 1874, p. 174, on “Dielectric Absorption”; Robison, “Mechan. Phil.”; Leslie, “Geomet. Anal.”; “Jour. Roy. Inst.” for February 1831, Vol. I. p. 311 (Electrif. of ray of light); eighth “Britannica,” Vols. I, sixth dissertation; VIII. pp. 532–533, 539, 542, 544, 552, 601, 607, 617; XIV. pp. 68, 663; XXI. pp. 612, 622, 628, 630; ninth “Britannica,” Vol. IX. pp. 29–31; Brockhaus, “Conversations-Lexikon,” Vol. VI. pp. 565–566; “Lond. and Edin. Ph. Mag.,” Vol. I. p. 161 for letter of Faraday of July 27, 1832, enclosing one signed P. M., “in which chemical decomposition is for the first time obtained by the induced magnetic current”; Faraday and Schönbein (“London and Edin. Mag.,” July-August 1836; “Roy. Instit. Proc.,” III. 70–71); Faraday and Riess, “On the action of non-conducting bodies in electric induction,” 1856; Sturgeon, “Sc. Res.,” 1850, pp. 20, 475; “Practical Mechanic,” Vols. II. pp. 318, 408; III. p. 197; “Libr. of Useful Knowledge” (Elec. Mag.), pp. 18, 99; Humboldt, “Cosmos,” Vol. I. pp. 182, 188; Harris, “Rud. Magn.,” 1852, I and II, pp. 61–69, etc., 199; III. 122–128 and “Rud. Elec.,” 1st ed., pp. 33–34; “Edin. Jour. Sc.,” 1826, Vol. III. p. 373; “Edin. new Ph. Jour.,” Vol. LI. p. 61; Golding Bird’s “Nat. Phil.,” p. 227; James Johnstone, “The Ether Theory of 1839,” pp. 26, 37; Noad, “Manual,” pp. 59, 236, 692, 805, 866; “Am. Jour. Sc.” for April 1871, relative to lines of magnetic force; “Ann. of Phil.” for 1832; “Bibl. Univ. Archives,” Vol. XVI. p. 129; “Roy. Instit. Proc.,” Vol. I, 1851–1854, pp. 56, 105, 216, 229; Phil. Trans., 1832, p. 163; 1851, pp. 29, 85; 1852, pp. 25, 137; Phil. Mag., Vol. III, 1852, p. 401; Dredge, “Elect. Illum.,” Vol. I. pp. 46, 91, 95; “New Eng. Mag.” for March 1891; Silliman’s Journal, Vol. XII. p. 69; “Sc. Am. Suppl.,” Nos. 198, p. 3148; 206, p. 3284; 526, p. 8404; 547, p. 8733; 652, p. 10416; La Lum. Electrique for October 31, 1891, pp. 202–203; Marcel Joubert, “Leçons,” 1882, Vol. I. pp. 495, 559; 576; Th. du Moncel, “Exposé des App. de l’Elec.,” 1872, Vols. I and II; G. B. Prescott, “Electricity,” 1885, Vol. I. pp. 105–112; “Reports of the Smithsonian Institution” for 1857, pp. 372–380; for 1862, p. 204; for 1889, p. 444; Richard Mansill, “New Syst. of Univ. Nat. Science,” 1887, pp. 180–185; “Faraday’s Researches on Electrostatical Induction,” also “Faraday’s Law of Attractions and Repulsions,” at pp. 26–30, and 647–664 of “Reprint of Papers on Electro-statics and Magnetism,” by Sir Wm. Thomson, London, 1884; “Essays in Historical Chemistry,” T. E. Thorpe, London, 1894, p. 142; “Life and Letters of Thomas Henry Huxley,” by Leonard Huxley, New York, 1901, as per Index at pp. 513–514; “Fragments of Science,” by John Tyndall, New York, 1901, Vol. I. pp. 420–443; “Jnl. of Psychological Medicine,” by Dr. William A. Hammond, New York, 1870, pp. 555–569; “Cat. Sc. Papers ... Roy. Soc.,” Vol. II. pp. 555–561; Vol. VI. p. 653; Vol. VII. p. 638; “Bibl. Britan.,” Vol. XVIII, N.S. for 1821, p. 269; “Phil. Mag. and Jour. of Science,” 1833, Vol. III. pp. 18, 37, 38, 161, 253, 353, 460, 469, and Vol. XI, 1838, pp. 206, 358, 426, 430, 538.