The Rigidity of the Earth's Interior

Abstract

THE letter of Dr. T. J. J. See (NATURE, April 13, p. 559) deals with a subject of profound interest to students of the larger problems connected with physical geology. But it appears that, in Dr. See's treatment of the subject, he has overlooked an important point, which I dealt with in a paper read before Section C of the British Association at Birmingham in 1886. Therein I directed attention to the fact that “gravitation” is only a special instance of the law of universal attraction, and as a corollary to this, at any considerable depth within the sphere of the earth, an appreciable factor of what I may call negative gravity must be allowed for, owing to the counter-attraction of the mass of matter situated nearer the surface of the sphere; so that a body placed at the centre of gravity of the earth, whatever its mass or density, would have no weight at all.