Humboldt, that the dry continental parts of the crust of the earth have a mean density of from 2·4 to 2·6, and the dry and oceanic parts of 1·5, and accept Reich's later estimate of the mean total density at 5·58, then the inaccessible, internal parts of the earth must have a
Fig. 4.
mean specific weight of 9·66. Only the metals among the bodies in the accessible parts of the earth possess so great a density; we have a right, then, to believe that the nucleus of the earth possesses a metallic constitution.
The density of the other heavenly bodies is deduced from that of the earth, by observing the amount of attraction which two bodies exert upon each other, and upon a third, and, having ascertained the distances apart of the three bodies, calculating their mutual densities by approved mathematical formulas.—Die Natur.
