I. On the bodily tides of viscous and semi-elastic spheroids, and on the ocean tides upon a yielding nucleus

In a well-known investigation Sir William Thomson has discussed the problem of the bodily tides of a homogeneous elastic sphere, and has drawn therefrom very important conclusions as to the great rigidity of the earth.' Now it appears improbable that the earth should be perfectly elastic; for the contortions of geological strata show that the matter constituting the earth is somewhat plastic, at least near the surface. W e know also that even the most refractory metals can be made to flow under the action of sufficiently great forces.