Researches in physical geology. Part II

In this communication the author states that, having in Part I. (read to the Society in December 1846) endeavoured, by generalizing the hypothesis on which is usually founded the theory of the earth’s figure, not only to improve that theory, but also to establish a secure basis for researches into the changes which may have taken place, within and at the surface of the earth, during the epochs of its geological history, his object here is to discover relations between the interior structure of the earth and phenomena observed at its surface, and also the effects of the reaction of the fluid nucleus, described in Part I., upon the solid crust. This memoir is divided into sections, each containing a distinct investigation; and the statement of the geological results is given at the end. I. The Pressures of the Shell and Nucleus at their surface of contact . In the investigation of these pressures the earth is supposed to consist of a nucleus of fluid matter inclosed in a solid shell, the inner and outer surfaces of which are spheroidal, but nearly spherical; and both shell and nucleus are supposed to consist of strata varying in density according to some unknown inverse law of the radii. The pressure at the inner surface of the shell is conceived to be due to a constant pressure, which is the same for every point, and a variable pressure, arising from the difference in form of the surface of the nucleus and inner surface of the shell. On these suppositions, simple expressions for the pressure on any stratum of the nucleus and on the shell’s inner surface are deduced.