Abstract
A method is given to calculate tortional frequencies of an elastic sphere of variable density and elasticity. By this method, the tortional frequencies are calculated of the earth, the internal constitution of which is inferred from the study of body wave propagations within it. The period of fundamental tortional oscillation of the earth is shown to be 43.4 minutes. The phase velocity of the corresponding surface wave has a maximum value 6.90km/sec for a wavelength of about 10000km. The decrease of phase velocity for longer wave lengths may be due to the existence of the earth core at the depth of 2900km.
