Part 2 / Book 6 — Book VI (continued 12)

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.)

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.