A.D. 1776.—Borda (Jean Charles), French mathematician and astronomer, improves upon the work of Mallet (at A.D. 1769), and is the first to establish accurately the knowledge of the third and most important element of terrestrial magnetism, viz. its intensity.
To him is exclusively due the correct determination of the difference of the intensity at different points of the earth’s surface by measuring the vibrations of a vertical needle in the magnetic meridian. This he determined during his expedition to the Canary Islands, and his observations were first confirmed through additional experiments which the companion of the unfortunate La Pérouse, Paul de Lammanon, made during the years 1785–1787, and which were by him communicated from Macao to the Secretary of the French Academy.
References.—Borda’s biography in the “Eng. Cycl.,” and in the eighth “Britannica”; Walker, “Magnetism,” p. 182; Humboldt on magnetic poles and magnetic intensity, embracing the observations of Admiral de Rossel, and “Cosmos,” Vol. V. 1859, pp. 58, 61–64, 87–100; also Vol. I. pp. 185–187, notes, for the history of the discovery of the law that the intensity of the force increases with the latitude; Norman (A.D. 1576).
A.D. 1777.—Lichtenberg (Georg Christoph), Professor of Experimental Philosophy at the University of Göttingen, reveals the condition of electrified surfaces by dusting them with powder.
The figures, which bear his name, are produced by tracing any desired lines upon a cake of resin with the knob of a Leyden jar and by dusting upon the cake a well-triturated mixture of sulphur and of red lead. These substances having been brought by friction into opposite electrical conditions, the sulphur collects upon the positive and the lead upon the negative portions of the cake: positive electricity producing an appearance resembling feathers, and negative electricity an arrangement more like stars.
References.—Harris, “Frict. Elect.,” p. 89; eighth “Britannica,” Vol. VIII. p. 606; E. Reitlinger, “Sibven Abh. ...” (Wien Acad.); illustrations in Sc. Am. Suppl., No. 207, p. 3297; Noad, “Manual,” p. 132; Erxleben’s “Physikalische Bibliotek,” s. 514; L. F. F. Crell, Chemische Annalen for 1786; “Göttingisches Magazin,” J i., S ii., pp. 216–220; Lichtenberg’s “Math. u. Phys. Schriften,” etc., Vol. I. p. 478. See also Dr. Young’s “Lectures on Nat. Phil.,” London, 1807, Vol. II. pp. 119, 419 for additional references, and p. 426 for Lichtenberg’s “Table of Excitation.”
A.D. 1777.—Pringle (Sir John), a man of great scientific attainments—who was physician to the Duke of Cumberland as well as to the Queen’s household, became a baronet in 1766, and afterward received many distinguished honours from foreign learned bodies—resigns the Presidency of the English Royal Society, which he had held since the year 1772. In this, as will be seen at a later date, he was succeeded by Sir Joseph Banks (at A.D. 1820), who continued in the office a period of over forty-two years. The cause which led to his resignation is best given in the following extract from his biography in the English Cyclopedia:
“During the year 1777 a dispute arose among the members of the Royal Society relative to the form which should be given to electrical conductors so as to render them most efficacious in protecting buildings from the destructive effects of lightning. Franklin had previously recommended the use of points, and the propriety of this recommendation had been acknowledged and sanctioned by the Society at large. But, after the breaking out of the American Revolution, Franklin was no longer regarded by many of the members in any other light than an enemy of England, and, as such, it appears to have been repugnant to their feelings to act otherwise than in disparagement of his scientific discoveries. Among this number was their patron George III, who, according to a story current at the time, and of the substantial truth of which there is no doubt, on its being proposed to substitute knobs instead of points, requested that Sir John Pringle would likewise advocate their introduction. The latter hinted that the laws and operations of nature could not be reversed at royal pleasure; whereupon it was intimated to him that a President of the Royal Society entertaining such an opinion ought to resign, and he resigned accordingly.”
In Benjamin Franklin’s letter to Dr. Ingen-housz, dated Passy, Oct. 14, 1777, occurs the following: “The King’s changing his pointed conductors for blunt ones is therefore a matter of small importance to me. If I had a wish about it, it would be that he had rejected them altogether as ineffectual.” It was shortly after the occurrence above alluded to that the following epigram was written by a friend of Dr. Franklin:
“While you Great George, for knowledge hunt,