The results discussed in this paper were obtained about five years ago. Except for a brief reference in ‘B. A. Reports,' 1917 (“Seismology”) they have not been published. There were two reasons for this delay: (1) additional data were desired in a matter of somewhat critical importance in the measured properties of the earth; (2) my official duties left little spare time for the pursuit of a purely scientific branch of seismology which required a good deal of tentative numerical computation. At the present date it appears that one must abandon all hope that additional results which were expected from Russian observatories can be obtained. Moreover, it appears very doubtful if relevant data from any of the Allied countries can be expected for some years to come. Accordingly, publication of the results so far obtained now seems desirable, and may serve to show how urgent is the need for the equipment of a few seismological observatories capable of obtaining the data that are wanted.