Note 8 — Chapter 22

"Considering that the mean density of the whole earth is only about five and a half times that of water, and that the materials of which the crust of the earth is composed are all compressible in a greater or less degree, so that even at no very great depth the density of the different substances must be greatly increased by the mere pressure of the superincumbent materials, some philosophers have supposed that the effects of pressure must be counterbalanced by the expansive force of a great heat subsisting in the interior of the earth; and others that the earth is not solid, but merely a hollow shell of inconsiderable thickness."—Brande.