Chapter XXXV: Part XV: , xxxviii; Vol. VIII, first part, p. 361; Reply to Mr. W (1)

F. Cooke’s pamphlet, “The Elec. Teleg.: Was it Invented by Prof.
Wheatstone?” London, 1855; Du Moncel, Vol. III; “Telegraphic
Tales,” 1880, p. 42; J. D. Reid, “The Telegraph in America,”
1887, p. 71; Ure’s “Dict. of Arts,” etc., London, 1878, Vol. II
(Elect. Metal.), p. 230; T. P. Schaffner, “Tel. Man.,” 1859, pp.
147–156; Silliman, “Principles of Physics,” 1869, p. 617; “Edin.
Phil. Journal,” 1823, Vol. IX. pp. 322, 395.

=A.D. 1816.=--Porret (Robert) (1783–1868) communicates to the _Annals of Philosophy_ (Vol. VIII. p. 74) a paper “On Two Curious Galvanic Experiments” (Electrovection, Voltaic Endosmose, or Electro-chemical Filtration).

He observed that when water was placed in a diaphragm apparatus, one side of which was connected with the positive and the other side with the negative electrode of the battery, that a considerable portion of the liquid was transferred from the positive toward the negative side of the arrangement. It has since been found that the same result occurs in a minor degree when saline solutions are electrolyzed, and, generally, the greater the resistance which the liquid offers to electrolysis the greater is the amount which is thus mechanically carried over.... It appears from the researches of Wiedemann (Pogg., _Ann._, Vol. LXXXVII. p. 321), which have been confirmed by those of Quincke, that the amount of liquid transferred, _cæteris paribus_, is proportioned to the strength or intensity of the current; that it is independent of the thickness of the diaphragm by which the two portions of liquid are separated; and that when different solutions are employed, the amount transferred in each case, by currents of equal intensity, is directly proportional to the specific resistance of the liquid. Miller, from whom the above is taken, says that this transfer has been minutely studied by Quincke, and gives an account of the latter’s work extracted from the _Ann. de Chimie_, LXIII. p. 479. Brewster’s allusion to Porret and Wiedemann (eighth “Britannica,” Vol. VIII. p. 630) is followed by the statement that Mr. Graham considers ordinary endosmose as produced by the electricity of chemical action.

REFERENCES.--Graham, Vol. II. p. 266; De la Rive’s
“Electricity,” Chap. IV. pp. 424–443; “Roy. Soc. Cat. of Sci.
Papers,” Vol. IV. pp. 987, 988; Wm. Henry, “Elem. of Exp. Chem.”
1823, Vol. I. p. 178; C. Matteucci, “Traité des Phénom. Elect.
Phys.,” 1844, p. 262 for Porret and Becquerel; Sturgeon’s “Sc.
Researches,” Bury, 1850, p. 544; Poggendorff, Vol. II. p. 503;
“Bibl. Britan.,” Vol. III, N.S., 1816, p. 15 (Thomson’s “Annals”
for July 1816).

=A.D. 1817.=--Mr. J. Connolly makes known through an English and French pamphlet, entitled “An Essay on Universal Telegraphic Communication,” the details of his portable telegraph.

As shown in the thirty-sixth volume of the _Transactions of the Society of Arts_ and in the twenty-fourth volume of the “Penny Cyclopædia,” his apparatus consists merely of three square boards painted with simple devices, like triangles, crescents, etc., the colours on the one side being the reverse of those on the other. Each of the six figures thus obtained is capable of producing four different distinct signals, making in all twenty-four, by successively turning each side of the board downward. In experiments made at Chatham, boards only eighteen inches square were found to answer for a distance of two miles, with a telescope having a magnifying power of twenty-five; and Mr. Connolly had also, it is said, exhibited these signals between Gros-nez and Sarque, a distance of seventeen miles, with boards twelve feet square.

At pp. 205, 208, of the _Transactions of the Society of Arts_, 1818, Vol. XXXV, and at p. 98, Vol. XXXVI for 1819, will be found Mr. Connolly’s system of telegraphing by means of flags in manner different from that of Lieut.-Col. John Macdonald alluded to at Pasley, A.D. 1808.

=A.D. 1817.=--In the “Encycl. Brit.” article treating of the influence of magnetism on chemical action, it is said that M. Muschman, Professor of Chemistry in the University of Christiania, made experiments to ascertain the effect of the earth’s magnetism on the precipitation of silver.

Desirous of explaining the chemical theory of the tree of Diana (_Arbor Dianæ_, first observed by Leméry), “he took a tube like a siphon and poured mercury into it, which accordingly occupied the lower part of the two branches; above the mercury he poured a strong solution of nitrate of silver. He then placed the two branches of the siphon so that the plane passing through them was in the magnetic meridian, and after standing a few seconds the silver began to precipitate itself with its natural lustre; but it accumulated particularly in the northern branch of the siphon, while that which was less copiously precipitated in the other branch had a less brilliant lustre, and was mixed with the mercurial salt deposited from the solution.” Muschman and Prof. Hansteen, having repeated this experiment with the same result, concluded that the magnetism of the earth had an influence on the precipitation of silver from a solution of its nitrate, and Muschman inferred from the experiment the identity of galvanism and magnetism (eighth “Britannica,” Vol. XIV. p. 42).

=A.D. 1817.=--Freycinet (Claude Louis Desaulses de) (1779–1842), captain in the French navy, is sent in command of an expedition fitted out by the French Government for the purpose of making scientific observations in a voyage round the world. The experimental stations were the Island of Rawak (near the coast of Guinea), Guam (one of the Ladrones), the Isle of France, Mowi (one of the Sandwich Islands), Rio Janeiro, Port Jackson, Cape of Good Hope, Paris and the Falkland Islands, as described in his “Voyage Autour du Monde ...” Paris, 1842.

His observations on the diurnal variations of the needle, which confirm the investigations made by Lieut.-Col. John Macdonald (A.D. 1808), are to be found at p. 54, Vol. XIV of the eighth “Britannica.”

REFERENCES.--His “Voyage de Découvertes ... 1800–1804 ...” (F.
Péron and Louis Freycinet), also his “Navigation et Géog. ...”
1815; the note at p. 158, Vol. I of Humboldt’s “Cosmos,” London,
1849; _Phil. Mag._, Vol. LVII. p. 20.

=A.D. 1817.=--In Vol. XLII. pp. 165, 166, of the _Transactions of the Society of Arts_ will be found a record of the explanation of his magnetic guard for needle pointers which Mr. Westcott made before the Committee of Mechanics during the year 1817. This is said to consist of several “bar magnets smeared over with oil placed in a frame behind the grindstone.”

=A.D. 1818.=--Bostock (John) (1774–1846), English physician, F.R.S., lecturer at Guy’s Hospital, publishes in London his “Account of the History and Present State of Galvanism,” which is scarcely more than a compilation of works treating of that branch of science.

One of the passages is, however, worth quoting, for it reflects the opinion shared by many physicists of the time that the resources of the galvanic field were already wellnigh exhausted. It thus appears at p. 102: “Although it may be somewhat hazardous to form predictions respecting the progress of science, I may remark that the impulse which was given in the first instance by Galvani’s original experiments, was revived by Volta’s discovery of the pile, and was carried to the highest pitch by Sir H. Davy’s application of it to chemical decomposition, seems to have, in a great measure, subsided. It may be conjectured that we have carried the power of the instrument to the utmost extent of which it admits; and it does not appear that we are at present in the way of making any important additions to our knowledge of its effects, or of obtaining any new light upon the theory of its action.”

Bostock is also the author of “Outline of the History of the Galvanic Apparatus”; “On the Theory of Galvanism” (_Nicholson’s Journal_ for 1802); “On the Hypothesis of Galvanism” (_Annals of Philosophy_, III, 1814), and of other works upon different scientific subjects. Reference is made by Mr. William Leithead (“Electricity,” London, 1837, Chap. VI. pp. 296, 297) to Bostock’s “Elementary System of Physiology,” 1827, Vol. II. pp. 413, etc., wherein is shown among other results, that, contrary to the views of Dr. Philip, there is no necessary connection between “the nervous influence” and the action of the glands. At p. 306 of Leithead appears another extract, from the third volume of Bostock, relative to the application of the electro-physiological theory in elucidating the phenomena of disease.

REFERENCES.--Poggendorff, Vol. I. pp. 249, 250; “Nicholson’s
Journal,” Vols. II. p. 296, and III. p. 3; Figuier, “Expos. et
Histoire,” 1857, Vol. IV. p. 425; Gilbert, Vol. XII. p. 476.

=A.D. 1819.=--Hansteen (Christoph) (1784–1873), Norwegian astronomer and physicist, embodies in his notable work, “Untersuchungen über den Magnetismus der Erde ...” (“Inquiries regarding the magnetism of the earth”), the result of his extensive researches concerning terrestrial magnetism, the account of which is accompanied by a chart indicating the magnetic direction and dip at numerous places. This work, which is said to have been practically completed in 1813 (Humboldt, “Cosmos,” 1859, Vol. V. p. 66), was translated by the celebrated Peter Andreas Hansen (Poggendorff, Vol. I. pp. 1013–1015) from the original manuscript and published in German. It attracted much attention throughout the scientific world, and so highly was it thought of that in almost all the voyages of discovery afterwards undertaken most magnetic observations were made according to its directions.

Through the “Encyclopædia Britannica” we learn that Hansteen’s able work was first made known in England by Sir David Brewster through two articles in the _Edin. Phil. Journal_ for 1820, Vol. III. p. 138, and Vol. IV. p. 114, and that an account of his subsequent researches, drawn up by Hansteen himself, appeared in the _Edin. Journal of Science_ for 1826, Vol. V. p. 65. It is also stated that the Royal Society of Denmark proposed in 1811 the prize question, “Is the supposition of one magnetical axis sufficient to account for the magnetical phenomena of the earth, or are two necessary?” Prof. Hansteen’s attention had been previously drawn to this subject by seeing a terrestrial globe, on which was drawn an elliptical line round the south pole and marked _Regio polaris magnetica_, one of the foci being called _Regio fortior_, and the other _Regio debilior_. As this figure professed to be drawn by Wilcke, from the observations of Cooke and Furneaux, Hansteen was led to compare it with the facts; and the result of his researches was favourable to that part of Halley’s theory which assumes the existence of four poles and two magnetic axes. Hansteen’s Memoir, which was crowned by the Danish Society, forms the groundwork of his larger volume published in 1819. “In his fifth chapter, on the Mathematical Theory of the Magnet, he deduces the law of magnetic action from a series of experiments similar to those of Hauksbee and Lambert.... In determining the intensity of terrestrial magnetism Professor Hansteen observed that the time of vibration of a horizontal needle varied during the day. Graham had previously suspected a change of this kind, but his methods were not accurate enough to prove it. Hansteen found that the minimum intensity took place between ten and eleven a.m., and the maximum between four and five p.m. He concluded also that there was an annual variation, the intensity being considerably greater in winter near the perihelion, and in summer near the aphelion; that the greatest monthly variation was a maximum when the earth is in its perihelion or aphelion, and a minimum near the equinoxes; and that the greatest daily variation is least in winter and greatest in summer. He found also that the aurora borealis weakened the magnetic force, and that the magnetic intensity is always weakest when the moon crosses the equator.”

According to Dr. Whewell (“History of Induc. Sciences,” 1859, Vol. II. p. 226), the conclusions reached by Hansteen respecting the position of the four magnetic “poles” excited so much interest in his own country that the Norwegian Storthing, or Parliament, by a unanimous vote provided funds for a magnetic expedition which he was to conduct along the north of Europe and Asia, and this they did at the very time when, strange to say, they refused to make a grant to the King for building a palace at Christiania. The expedition was made in 1828–1830, and verified Hansteen’s anticipations as to the existence of a region of magnetic convergence in Siberia, which he considered as indicating a “pole” to the north of that country. The results were published in Hansteen and Due’s “Resultate magnetischer ...” (“Magn., Astron. and Méteor. Obs. on Journey through Siberia”) which appeared in 1863.

In the Sixth Dissertation, Chap. VII of the “Encycl. Brit.,” it is said that, next to Prof. Hansteen, science is mainly indebted for the great extension of our knowledge of the facts and the laws of terrestrial magnetism to two illustrious German philosophers, Baron Alexander von Humboldt and Prof. Karl Friedrich Gauss (1777–1855). An account is therein given of Gauss’s individual investigations, as well as of the researches he made in conjunction with Wilhelm Eduard Weber (1804–1891), who was likewise a professor at Göttingen. Of Alex. von Humboldt, we have spoken fully under date 1799, and of Gauss and Weber, mention has already been made at Schilling (A.D. 1812).

The very valuable contributions of Gauss and Weber appear throughout all the many scientific publications of the period, notably in the “Abhandlung d. Gött. Geselsch. d. Wiss.,” their joint work being shown to advantage in the important “Resultate ... des Magnet. Vereins,” published in Leipzig, 1837–1843.[58]

REFERENCES.--For M. Hansteen’s scientific papers and for an
account of additional magnetic results obtained by himself and
others, consult the eighth “Britannica,” Vols. I. p. 745; IV.
p. 249; XIV. pp. 15, 23, 42 (experiment with M. Muschman), 50,
55, 57–64, _et seq._, for Morlet and others; Thomson’s “Outline
of the Sciences,” London, 1830, pp. 546–548; Whewell, “History
of the Induc. Sci.,” Vol. II. pp. 613, 615, also p. 219 for
Yates and Hansteen; Johnson’s new “Univer. Encycl.,” 1878, Vol.
III. pp. 231–234 for Morlet, etc.: Weld’s “Hist. of Roy. Soc.,”
Vol. II. p. 435; “Edin. Jour. of Sci.,” London, 1826, Vols. I.
pp. 87, 334; V. pp. 65–71, 218–222; “Report of Seventh Meeting
British Association,” London, 1838, Vol. VI. pp. 76, 82; J.
G. Steinhauser’s articles published between 1803 and 1821;
Harris’ “Rudimentary Magnetism,” London, 1852, Part. III. pp.
38, 39, 111; _Phil. Mag._, Vol. LIX. p. 248, and _Phil. Mag._
or _Annals_, Vol. II. p. 334; “Zeitschr. f. pop. Mitth.,” I. p.
33; Schweigger’s _Journal_, 1813–1827; Poggendorff’s _Annalen_,
1825–1855; “Académie Royale de Belgique” for 1853, 1855,
1865; C. Hansteen and C. Fearnley, “Die Univ.-Sternwarte ...”
1849; Hansteen, Lundh and Muschman, “Nyt. Mag. for Naturvid,”
1823–1856. See likewise his biography in the “English Cyclop.
Supplement,” pp. 642, 643; “Catal. Roy. Soc. Sc. Pap.,” Vol.
III. pp. 167–172; Vol. VI. p. 681, Vol. VII. p. 905; Houzeau
et Lancaster, “Bibl. Gén.,” Vol. II. p. 157; “Edin. Phil.
Journal,” 1823, Vol. IX. p. 243; “Annual Rec. Sc. Disc.,” 1873,
p. 683; 1875, p. 155; Knight’s “Amer. Mech. Dict.,” 1875, Vol.
II. p. 1374, and eighth “Britan.,” Vol. XIV. p. 49, regarding
Hansteen’s lines of no variation for 1787; Humboldt’s “Cosmos,”
1859, Vol. V. pp. 110–111, for the investigations of Hansteen,
Sir Ed. Belcher and others, those of the last named being
treated of at p. 493 of the _Phil. Trans._ for 1832; Noad,
“Manual,” pp. 529, 530, 534, 616, 617, etc.; Appleton’s “New Am.
Cycl.,” Vol. XI. p. 64.

=A.D. 1819.=--Hare (Robert) (1781–1858) who was for twenty-nine years Professor of Chemistry in the Pennsylvania University, publishes in Philadelphia “A New Theory of Galvanism, Supported by Some Experiments and Observations Made by Means of the Calorimotor ...” of which an English edition appears in London the same year. (A full review of this work is to be found more particularly at p. 206, Vol. LIV of the _Philosophical Magazine_; in the “Encycl. Metropol.,” Vol. IV (Galvanism), p. 222; in Ure’s “Dictionary of Chemistry,” Am. ed., article “Calorimotor”; at p. 187 of the _Phil. Trans._ for 1823; at pp. 409, 410, Vol. I of Gmelin’s “Chemistry,” and at pp. 413–423, Vol. I of Silliman’s _Am. Jour. of Sci._, the last named being accompanied by a very fine illustration of the Calorimotor.)

This apparatus, which has already been alluded to (Pepys, A.D. 1802), consists of sheets of zinc about 9 inches by 6, and of copper about 14 inches by 6, coiled around one another nearly half an inch apart; there being in all 80 coils, 2½ inches in diameter, which are let down by means of a lever into glass vessels containing the acid solution. Dr. Hare observes:

“Volta considered all galvanic apparatus as consisting of one or more electromotors, or movers of the electric fluid. To me it appeared that they were movers of both heat and electricity; the ratio of the quantity of the latter put in motion to the quantity of the former put in motion being as the number of the series to the superficies. Hence the word _electromotor_ can only be applicable when the caloric becomes evanescent, and electricity almost the sole product, as in De Luc’s and Zamboni’s columns; and the word _calorimotor_ ought to be used when electricity becomes evanescent and caloric appears the sole product.”

“It afterwards appeared quite natural,” remarks Mr. W. B. Taylor (Note B, “Mem. of Jos. Henry,” p. 376) “to distinguish these classes of effects by the old terms--‘intensity’ for electromotive force, and ‘quantity’ for calorimotive force. There is obviously a close analogy between these differences of condition and resultant, and the more strongly contrasted conditions of mechanical and chemical electricity; and indeed the whole may be said to lie in a continuous series, from the highest ‘intensity’ with minimum quantity, to the greatest ‘quantity’ with minimum intensity.”

Two years later (1821), Dr. Hare constructed his _galvanic deflagrator_. It consists of two pairs of troughs, each ten feet long, and containing 150 galvanic pairs, so arranged that the plates can all be simultaneously immersed into or withdrawn from the acid. Each pair turns on pivots made of iron, coated with brass or copper, and a communication is established between these and the voltaic series within by means of small strips of copper. The “Encycl. Brit.” gives a full description of the construction and working of the apparatus, as do also the “Encycl. Metropol.,” Vol. IV (Galv.), p. 176; Noad (“Manual,” pp. 266, 267); Gmelin (“Chemistry,” Vol. I. pp. 409, 410), and Silliman (“Journal of Sci. and Arts,” Vol. VII. p. 347). The first-named publication says of Dr. Hare’s _deflagrator_:

“A brilliant light, equal to that of the sun, was produced between charcoal points, and plumbago and charcoal were fused by Profs. Silliman and Griscom. By a series of 250, baryta was deflagrated, and a platina wire, three-sixteenths of an inch in thickness, ‘was made to flow like water.’ In the experiments with charcoal, the charcoal on the copper side had no appearance of fusion, but a crater-shaped cavity was formed within it, indicating that the charcoal was volatilized at this side and transferred to the other, where it was condensed and fused, the piece of charcoal at this pile being elongated considerably. This fused charcoal was four times denser than before fusion. In a letter from Prof. Silliman, which was transcribed in the _Sc. Am. Sup._ for Sept. 21, 1878, he says: ‘Undoubtedly the earliest exhibitions of electric light from the voltaic battery were those made with the deflagrators of Dr. Hare by Prof. Silliman at New Haven in 1822, and subsequently on a magnificent scale at Boston in 1834, when an arc of over five inches diameter was produced by the simultaneous immersion of 900 large-sized couples of Hare’s deflagrator. But no means had then been devised for the regulation of the electric light to render it constant, and although the writer as early as 1842 used this light successfully to produce daguerreotypes, the progress of invention had yet to make further use of the discovery of science before electrical illumination was possible.’”

The description of Dr. Hare’s electrical machine (before alluded to at Van Marum A.D. 1785), wherein the plate is mounted horizontally so as to show both negative and positive electricity, was published in London during 1823, and can be found in Vol. LXII of the _Phil. Mag._, as well as at pp. 538, 604, 605, Vol. VIII of the 1855 “Encycl. Brit.” In the last-named article mention is made of the introduction of a band (illustrated Fig. 7, Plate CCXXII) which prevents the plate from being cracked, as it frequently is, through some hasty effort to put it in motion while it adheres to the cushions. It is also therein stated that in order to offset the heavy expense attending the breakage of large cylinders and plates, M. Walkiers de St. Amand, of Brussels, among many others, made an apparatus of varnished silk 25 feet long and 5 feet wide, capable of giving sparks 15 inches long (see A.D. 1785), while Dr. Ingen-housz constructed machines with pasteboard discs four feet in diameter, soaked in copal or amber varnish dissolved in linseed oil, which gave sparks of one and even two feet in length.

In the fifth volume, new series, of the _Amer. Phil. Trans._ will be found Dr. Hare’s “Description of an Electrical Machine,” with a plate four feet in diameter, so constructed as to be above the operator; also of a battery discharger employed therewith, and some observations on the causes of the diversity in the length of the sparks erroneously distinguished by the terms positive and negative. Hare is also the inventor of a single gold-leaf electroscope of such great delicacy that it has, he says, enabled him to detect the electricity produced by one contact between a zinc and copper disc, each six inches in diameter (Noad, “Manual,” p. 29; Harris’ “Rudim. Elect.,” p. 50; Silliman’s _Journal_, Vol. XXXV). He invented several other electrical appliances, and he is likewise the author of numerous important memoirs which it would be impossible to detail in the narrow limits of this “Bibliographical History.” They will, however, be found recorded in the publications named below.

REFERENCES.--_Phil. Trans._ for 1769, Vol. LXIX. p. 659. See
also, for Walkiers de St. Amand, the entry at A.D. 1785, as
well as Lichtenberg’s _Magazin_, Vol. III, 1st, p. 118, for the
last-named year. To these might be added the machines made by
Mundt, of silken strips (Gren’s _Journal der Physik._, Vol. VII.
p. 319); by N. Rouland, “Descript. des mach, elec. à taffetas,”
Amsterdam, 1785; by Croissant and Thore; of paper by W. H.
Barlow (_Phil. Mag._, Vol. XXXVII. p. 428), of gutta percha;
as well as machines of rubber by Fabre and Kunneman, as shown
at Th. Du Moncel’s “Exposé des appl. de l’El.,” second ed., p.
399, and third ed., 1872, Vol. II. pp. 78, 122, 265, besides the
peculiarly constructed machines of Erdmann Wolfram (Ferussac,
“Bulletin des Sciences Tech.” for 1824); of G. H. Seiferheld,
“Beschreib ... elektrische mach,” 1787; of F. E. Neuman, as
modified by F. Zantedeschi (“Ann. Sci. Lom.-Ven.,” XII. p. 73),
and of those described at p. 420, Vol. II, and at p. 4, Vol.
III of _Nicholson’s Magazine_. Consult likewise, pp. 335, 340,
second Am. ed. of the “New Edin. Encycl.,” 1817. Poggendorff,
Vol. I. pp. 1018, 1019; “Cat. Sci. Papers of Roy. Soc.,” Vol.
III. pp. 177–182; Vol. VI. p. 182; Silliman’s _Am. Jour. Sci.
and Arts_, Vols. II. pp. 312, 326; III. p. 105; IV. p. 201; V.
p. 94; VII. pp. 103, 108, 351; VIII. pp. 99, 145; X. p. 67;
XII. p. 36; XIII. p. 322; XV. p. 271; XXIV. p. 253, XXV. p.
136; XXXI. p. 275; XXXII. pp. 272, 275–278, 280–285; XXXIII. p.
241; XXXV. p. 329; XXXVII. pp. 269, 383; XXXVIII. pp. 1, 336,
339; XXXIX. p. 108; XL. pp. 48, 303; XLI. p. 1, and XLIII. p.
291; _Phil. Mag._, Vols. LVII. p. 284; LXII. pp. 3, 8, etc.;
_Phil. Mag._ or _Annals_, Vol. VI. pp. 114, 171; _Journal of
the Franklin Institute_, third series. Vol. XV. pp. 188, etc.;
_Trans. of the Am. Phil. Soc._, N.S., Vol. VI. p. 297 (for Hare
and Allen) also pp. 339, 341, 343, and Vol. VII for 1841; “Mem.
Jos. Henry,” Washington, 1880, p. 82; Figuier, “Exp. et Hist.,”
1857, Vol. IV. pp. 391, 401, 402; Dr. Thomas Thomson, “Outline
of the Sc.,” London, 1830, pp. 515, 517; Appleton’s “New
Amer. Cycl.,” Vol. VII. p. 66; Appleton’s “Dict. of Machines,
Mechanics ...” 1861, pp. 432, 433; Dr. William Henry, “Elem. of
Exper. Chem.,” London, 1823, Vol. I. p. 169, and Supplement,
Chap. VII. p. 29; “Annual of Sc. Disc.” for 1862, p. 99.

=A.D. 1819.=--Gmelin (Leopold), the most distinguished member of the family of that name, publishes, at Frankfort, 1817–1819, the first edition of his celebrated “Handbuch d. theoret. Chemie,” which embodies the whole extent of chemical science as it then existed and the fourth and last edition of which, under the author’s supervision, appeared during 1843–1845. This extensive work is well known, both in its original form and through the very able translation of it made by Mr. Henry Watts. In the report of the Council of the Chemical Society for 1854, it is said that “the greatest service which Gmelin rendered to science--a service in which he surpassed all his predecessors and all his contemporaries--consists in this: that he collected and arranged in order all the facts that have been discovered in connection with chemistry. His Handbuch der theoret Chemie stands alone. Other writers on chemistry have indeed arranged large quantities of materials in systematic order, but for completeness and fidelity of collation and consecutiveness of arrangement, Gmelin’s Handbuch is unrivalled.”

Although many references have been made herein to Leopold Gmelin’s treatment of such departments of science as directly appeal to the readers of this compilation, it is well to mention some of the headings under which they are to be found. They are, “Electricity,” “Electro-chemical Theories,” “Electrolysis,” “Technical Apparatus of Electricity,” “Theory of Galvanism,” “Galvanic Batteries,” “Magnetic Condition of All Matter,” etc., etc., the whole occupying pp. 304 to 519, Vol. I of Gmelin’s English edition. The list of many of Leopold Gmelin’s valuable contributions to science is given in the “Catalogue Sc. Papers Roy. Soc.,” besides which may be mentioned his “Uber e angebl. meteorische masse” (Gilbert, _Annalen_, LXXIII for 1823), and his “Versuch einer elektro-chemisch. theorie” (Poggendorff’s _Annalen der Physik und Chemie_, Vol. XLIV for 1838, while at pp. 547–550 of Mr. J. J. Griffin’s able work, published in London during 1858, will be found the results obtained by Prof. G. Magnus and by Prof. Faraday with a summary of Gmelin’s conclusions under the heading of “The Evidence of Electrolysis in Favour of the Radical Theory.”

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.)”]