One year before that (1807) Pepys constructed a new form of eudiometer, of which a description was given before the Royal Society on the 4th of June, as shown at p. 270 Vol. I of the “Abstracts of Papers,” etc., of that Institution, as well as in the 1807 volume of the Philosophical Transactions.
Of the many ingenious experiments by which Pepys distinguished himself, scarcely none attracted more attention than those which are referred to in the last-named Transactions for 1866, pp. 339–439. It is only since 1815, when he employed the electric current to heat iron wire and diamond dust together, whereby he obtained steel, that the direct carburization of iron by the diamond has been clearly established. Prior to this date, during 1798, Clouet had melted a little crucible of iron weighing 57·8 grammes containing a diamond weighing 0·907 gramme, and produced a fused mass of steel. Guyton de Morveau reported upon Clouet’s experiment in the Annales de Chimie for 1799 (Vol. XXXI. p. 328) and his investigations were repeated by many scientists, notably by Margueritte, as recently as 1865. The latter’s observations, which were communicated to the Annales de Chimie et de Physique (Tome VI), showed that, although carburization can be effected by simple contact of carbon and iron in a gaseous atmosphere, it is nevertheless true that in the ordinary process of cementation the carbonic oxide gas plays an important part, which had until then been overlooked (Translation of Prof. W. C. Roberts-Austen, F.R.S. For Mr. Children’s investigations in the same line, see the Phil. Trans. for 1815, p. 370, also A.D. 1809).
Sir Humphry Davy employed in his experiments on the decomposition and composition of the fixed alkalies two mercurial gasometers of Pepys’ design, described in No. 14 of the Phil. Trans. for 1807, in conjunction with the same apparatus used by Messrs. Allen and Pepys for the combustion of the diamond (“Bakerian Lectures,” London, 1840, pp. 84 and 93).
During the year 1822 Pepys constructed for electro-magnetic experiments a very large spiral galvanic battery, which was put together for the London Institution on the plan of the one first built by Dr. Robert Hare, Professor of Chemistry in the University of Pennsylvania. Pepys called it a calorimotor, by reason of its remarkable power of producing heat, and it is well illustrated in the 8th Edit. “Encyclopædia Britannica” article on “Voltaic Electricity.” It consisted only of two metallic sheets, copper and zinc, fifty to sixty feet long by two feet wide, coiled around a cylinder of wood and prevented from coming together by three ropes of horse-hair, the whole being suspended over a tub of acid so that, by a pulley or otherwise, it could be immersed or taken up. As stated in Vol. V of the Trans. of the Amer. Phil. Soc., this battery required nearly fifty-five gallons of fluid, and the solution used contained about one-fortieth of strong nitrous acid.
When, as Noad observes, it is stated that a piece of platinum wire may be heated to redness by a pair of plates only four inches long and two broad, the calorific power of such an arrangement as the above may be imagined to have been immense. The energy of the simple circle depends on the size of the plates, the intensity of the chemical action on the oxidizable metal, the rapidity of its oxidation, and the speedy removal of the oxide. Pouillet is said to have constructed one of these batteries with twelve couples for the Paris Faculté des Sciences, and found it very powerful in producing large quantities of electricity with low tension. The best liquid for this battery was water with one-fortieth in volume of sulphuric acid and one-sixtieth of nitric acid. With the above-described battery of Mr. Pepys, Sir Humphry Davy performed a remarkable experiment which is to be found described in the Phil. Trans. for 1823. A similar apparatus was produced independently, at about the same time, by Dr. Seebeck, of Berlin.
Another of Pepys’ inventions is the substitution, for the tinfoil coatings within the glass of Bennet’s electroscope, of two plates, forming an acute angle, which, by means of a regulating screw, can be adjusted to any required distance from the gold leaves. The angular part is secured to the bottom; the open part perpendicularly upward. By this mode of approximating the coatings to the gold leaves, the resistance being diminished, a weaker intensity of electricity suffices for their disturbance.
References.—Quarterly Journal of Science, Vol. I for 1816; Phil. Mag., Vol. XXI. p. 241; XLI. p. 15; Becquerel, Vol. I. p. 34. Mr. William H. Pepys, Jr., published descriptions of the newly invented galvanometer and of the large galvanic apparatus in the Phil. Mag., Vol. X., June 1801, p. 38, and Vol. XV for 1803, p. 94; “Cat. Sc. Papers Roy. Soc.,” Vol. II. p. 192; “Bibl. Britan.,” Vol. XVIII, 1801, p. 343, and Vol. XXII, 1803, p. 297.
A.D. 1803.—Geoffroy Saint-Hilaire (Etienne), a very eminent French naturalist, once the pupil of Haüy, whose life he was the means of saving during the massacre of September 1792, is the first to give a thoroughly complete description of the electrical organs and functions of the raia torpedo, of the gymnotus electricus, of the silurus electricus, and of other similar species of fishes. His work on the subject, entitled “Sur l’anatomie comparée,” etc., is alluded to in Vol. I. An. xi. No. 5 of the “Annales du Museum,” whence it is translated for the fifteenth volume of the Phil. Mag.
His analyzation of the fluid in the cells of the torpedo showed it to consist of albumen and gelatine; and he discovered some organs analogous to those of the torpedo in different species of the same genus raia, which, strange to say, do not appear possessed of any electrical power.
The electrical organs of the silurus electricus he found to be much less complicated than those of other electrical fishes. They lie immediately below the skin and stretch all around the body of the animal. Their substance, he says, is a reticulated mass, the meshes of which are plainly visible, and these cells are filled, like those of other electrical fishes, with an albuminous gelatinous matter. The nerves distributed over the electrical organs proceed from the brain, and the two nerves of the eighth pair have a direction and nature peculiar to this species. (Consult C. Matteucci, “Traité des Phénomènes ...” Paris, 1844, Chaps. VI and VII. pp. 301–327.)