Davison's groundbreaking work on the seismic periods revolutionized the field of seismology. This book collects his most important research and presents it in an accessible format for both experts and laymen. The book includes detailed explanations of Davison's methods as well as fascinating observations of earthquakes and seismic activity around the world. A must-read for anyone interested in the science of earthquakes.This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it.This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work.Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.