A Manual of Seismology

Abstract

TIME was when the meaning of seismology was clear and unmistakable; it was the study of earthquakes, and by earthquakes was meant the disturbance which could be felt, and, When severe, caused alarm and damage. It was known that there was a central area where the earthquake was most severe, fringed by zones of decreasing violence, until a region was reached where it was insensible to the unaided senses, though still recognisable by suitable instruments, and when, towards the end of last century, it was found that,, at distances far away from the region affected by the sensible shock, disturbances which were clearly connected with great earthquakes could be detected by suitable instruments, it was natural to suppose that the origin was the same for both. Only of recent years has it been recognised that the earthquake proper, caused directly by fracturing of the surface rocks, is but a secondary effect of a more deep-seated disturbance, or bathyseism, which, and not the earthquake proper, is presumably the origin of the disturbance represented in the preliminary tremors of the distant record.

A Manual of Seismology.

By Dr. Charles Davison. (Cambridge Geological Series.) Pp. xii + 256. (Cambridge: At the University Press, 1921.) 21s. net.