Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/222

 The first calculation of the force of the drift from the poles was carried out by P. S. Epstein. He found the expression for the force K in the geographic latitude 𝜑 to be

where m is the mass of the continental block, d half the difference in altitude between the floor of the ocean and the surface of the continental block (or, equal to the difference in level of the centres of gravity of the block and of the displaced sima), and 𝜔 is the angular velocity of the earth.

He used this equation in order to calculate the coefficient of viscosity 𝜇 of the simasphere from the velocity of displacement of the continental blocks (according to the general formula K = 𝜇 $3⁄2$, where M is the thickness of the viscous layer), and obtained

where 𝜚 is the specific gravity of the block and s its thickness. Using now the following numerical values, which are certainly very extreme,

he found the coefficient of viscosity of the sima to be

thus being three times as great as that of steel at room-temperature. He concludes from this that “we can summarize the results thereof in the