PHILOSOPHICAL TRANSACTIONS.

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 later known as Lord Kelvin, a pioneer in thermodynamics and physics discussed the problem of the bodily tides tides that occur within the solid or semi-solid body of a planet, rather than just in its surface oceans of a homogeneous uniform in composition elastic sphere. From this study, he drew very important conclusions regarding the great rigidity of the Earth.

Now, it seems improbable that the Earth is perfectly elastic. The distortions seen in geological strata layers of rock show that the material constituting the Earth is somewhat plastic, at least near the surface. We also know that even the most heat-resistant metals can be made to flow under the application of sufficiently great force.

Although Sir William Thomson’s investigation has gone far to disprove the old idea that the Earth has a semi-fluid interior, geologists are still strongly impressed by the fact that enormous masses of rock are being—and have been—poured out of volcanic vents in the Earth's surface. Because of this, the belief is not yet extinct that we live on a thin shell over a sea of molten lava. Under these circumstances, it seems worthwhile to investigate the consequences of the theory that the matter making up the Earth is of a viscous viscous having a thick, sticky consistency between a solid and a liquid, like honey or tar or imperfectly elastic nature. If the interior is composed this way, then the solid crust—unless it is very thick—cannot possess enough rigidity to suppress the internal tidal surging. These hypotheses should yield results that correspond fairly well to reality. The hypothesis of imperfect elasticity will be prin—

* Sir William states that Gabriel Lamé original: "M. LAMÉ" had treated this subject at an earlier date, but in an entirely different manner. I am not aware, however, that Lamé had fully discussed the subject in its physical aspect.