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.”