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XIX. On the mean density of the Earth

1821; Royal Society; Volume: 111; Linguagem: Inglês

10.1098/rstl.1821.0020

2053-9223

History and Developments in Astronomy

Although the determination of the mean density of the whole terraqueous globe of our planet, is admitted to be a problem of the utmost importance to several branches of philosophy, particularly to physical astronomy, and the figure and constitution of the earth; it would seem, from the dis­cordancy of the declared opinions of some eminent philoso­phers, that the problem is still in an uncertain state. Since the first notice of this subject by Newton, in his admirable Principia, it has often been incidentally alluded to, without receiving a precise determination; with the exception of two instances only, in which it has been stated to be, certainly or approximately, determined by experiment; namely, in the case of the Schehallien experiment, by Dr. Maskelyne and myself, and by the Honorable Henry Cavendish, by a method invented by Mr. Michell. The former of these experiments was made by Dr. Maskelyne, in the years 1774, 1775, and 1776, by means of that large mountain in Scotland, in measuring its dimensions, and in comparing its attraction on a plummet, with that of the whole earth on the same; the calculations on it having been made by myself, and first published in the Philoso­phical Transactions of the year 1778; and since more correctly in the second volume of my Mathematical Tracts. The other experiment, by Mr. Cavendish, was by observing the attraction on small pendulous balls, of two inches di­ameter, by larger ones of ten inches diameter, as compared with the attraction of the earth on the same.