Now, it is not at all obvious, to what physical cause this phenomenon is to be ascribed. The earth, as it exists at present, has none of the conditions that render the assumption of the figure of equilibrium in any way necessary to it. Constituted as it is, its parts cohere with forces incomparably too great to obey the laws of statical pressure, or to assume any one figure rather than another, on account of the centrifugal tendency which results from its revolution on its axis. There is no necessity that its superficies should be every where level, or perpendicular to the direction of gravity, nor that every two columns, standing on the same base, any where within it, and reaching from thence to any two points of the surface, should be of such weights as precisely to balance one another. Neither of these, indeed, is at all conformable to fact. They are, however, the very suppositions on which the determination of the spheroid of equilibrium is founded; and as they certainly do in no degree belong to the earth, it seems strange that the result deduced from them should be in any way applicable to it. This coincidence remains, therefore, to be explained; and it must greatly enhance the merit of any geological system, if it can connect this great and enigmatical phenomenon with the other facts in the natural history of the earth. 430. To establish such a connection, has, accordingly, been a favourite object with geologists, whether they have embraced the Neptunian or Volcanic theory: both have thought that they were entitled to suppose the primeval fluidity of the globe, the one by water, and the other by fire; and in whatsoever way that fluidity was produced, the result of it could be no other than the spheroidal figure of the whole mass, agreeably to the laws of hydrostatics. If in this fluid state the earth was homogeneous, the spheroid would be accurately elliptical, and the compression at the poles would be 1/230 of the radius of the equator; if the fluid was denser toward the centre, the flattening would be less: and in either case, the body, as it acquired solidity, may be supposed to have retained its spheroidal figure with little variation. But though the fluidity of the earth will account for the phenomenon of its oblate figure, it may reasonably be questioned, whether this fluidity can be admitted, in consistency with other appearances. According to what is established above, none of the appearances in the mineral kingdom indicate more than a partial fluidity in any former condition of the earth. The present strata, made up as they are of the ruins of former strata, though softened by heat, have not been rendered fluid by it, and have even possessed their softness in parts, and in succession, not altogether, nor at the same time.