Page:Popular Science Monthly Volume 59.djvu/447

Rh philosophers. Blagden also made certain changes in the manuscript of Cavendish's 'Experiments on Air,' and while superintending, in his capacity of secretary of the Royal Society, the printing of the paper, and of Watt's rival essay, suffered certain typographical errors to occur, which involved himself and his principle in accusations of unfairness, in which, however, Wilson shows that with the exception of a carelessness in correcting printer's proof, Blagden was guiltless of any wrong toward Watt or of unfairness toward Lavoisier, and that to DeLuc belongs the unenviable distinction of deliberately provoking the water controversy, doing Cavendish and also Watt a great wrong by hastily deciding against the former, and filling Watt's mind with suspicions that Cavendish had borrowed from Watt's letter to Priestley the views which he published as his own, because he had in truth discovered them for himself, and that too at an earlier date (1781) than Watt (1784:) or Lavoisier (1784-86).

Remarkable as Cavendish's achievements in chemistry were, his greatest fame as a scientist will ever be based on his researches in physics; his single experiment in dynamics would place him in the first rank, and a very large part of the modern development of electrical science is based upon his work in electrostatics and electro-dynamics.

Cavendish verified the law of inverse squares for gravitational attraction, and determined the mean density of the Earth. The apparatus, devised by the Rev. John Michell, consisted of a horizontal lever six feet long, suspended by a wire forty inches in length, carrying at each end a lead ball two inches in diameter. Two large masses of lead (each about 317 lbs.) were placed near the ends of the lever and on opposite sides, so that, their attraction would produce turning moments in the same direction. The angle of rotation having been measured by means of telescopes with verniers, and the torsion of the suspending wire determined by observing the time of vibration of the rod, the force was calculated which would have been exerted by a globe of water the size of the earth on the same body on its surface, and from this the density of the earth was obtained as the mean of seventeen terminations to be 5.48 ± 0.38.

Cavendish cared more for investigation than for publication. He would undertake the most laborious researches in order to clear up a difficulty which none but himself could apprehend, or was even aware of, and we cannot doubt that the result of his enquiries gave him a certain degree of satisfaction. But it did not excite in him the desire to communicate the discovery to others which, in the case of ordinary men of science, generally ensures the publication of their results. How