Page:Great Neapolitan Earthquake of 1857.djvu/189

Rh In accordance with the theory of Leibnitz, we therefore have $$\mathrm{M} = $$ being the mass of the detached portion; $$V = $$ the velocity of the wave in its path (normal), $$f = $$ the perpendicular height of the centre of gravity above the base of fracture; $$\mathrm{F} = $$ the coefficient of dynamic cohesion, or the force upon the unit of surface of the material fractured, which, when suddenly applied, is sufficient to produce fracture; $$\mathrm{A} = $$ the area of the base of fracture in such units; $$k = $$ the radius of gyration of the plane of fracture with respect to the axis $$\mathrm{A}$$ or $$\mathrm{B}$$. $$\beta = $$ the width of $$\mathrm{AB}$$.

If $$\mathrm{W} = $$ the weight of the mass broken off, $$g = $$ the velocity due to gravity in one second, then and if the detached mass be any regular prism or right