RHYTHM IN EARTHQUAKES.

Evening Star, Issue 12843, 19 June 1906, Page 3

RHYTHM IN EARTHQUAKES.

Japan is a country which affords frequent opportunities for the study of earthquakes, and it is therefore quite in accordance with the fitness of things that the University of Tokio should contain a chair of seismology, and that the Mikado s Government should encourage the scientific observation of seismic phenomena. How this is done by means of stations dotted up and down the country was dcscntiea bv Professor John Milne, F.R.S., in the course of a lecture on ‘ Recent Advances in Seismology,’ delivered before the Royal (Society. Characteristically Japanese is one of the methods adopted—vis., that of carefully noting the habits and erica of pheasants, doer, and other animals kept m cages, these creatures being, it seems, susceptible to many influences which fail to affect human beings. Earthquakes, though due to comparatively small fractures of the earth’s crust, frequently displace masses of earth over largo areas—sometimes as much as half a million square miles in extent—and in the bod of the ocean differences in depth of 300 fathoms have been effected. Needless to say, they are often responsible for breakage of cables. On January 31 an earthquake originating I in South America was felt the same day in I the Antilles, where nine cables were broken. In Japan it is no unusual thing to experience a return shock from four to six minutes after the first, disturbance, the earthquake dying away with rhythmical vibrations like music. It is 'interesting to know that the speed at which earthquakes travel varies, according, to Professor Milne, from 11 kilometres per second in the first phase of the disturbance to 6 kilometres up to a distance of 120deg from the surface, and finally from 3.3 to 3.1 kilometres, the former being the maximum velocity on the surface of the earth.