Reviews 



Earthquakes: An Introduction to Seismic Geology. By William 

 Herbert Hobbs. New York: D. Appleton and Co., 1907. 

 Recent earthquake phenomena in North America have aroused such general 

 interest in the subject that there has arisen a well-defined demand for clearly- 

 written books on earthquakes, in which one could find the latest knowledge in 

 such a form as to be intelligible even to the layman. Professor Hobbs has set 

 himself the task of supplying this demand, and has been very successful in his 

 effort. He has given us a book which, though brief, outlines the main facts, 

 theories, and conclusions in a clear, direct, and simple manner. Moreover, he 

 brings the information down to date, which is a matter of great importance in a 

 science that has felt the impulse of new methods that, within a decade, have 

 almost revolutionized certain phases of the subject. 



In the first chapter there is a'brief summary of early theories for earthquakes, 

 including the simple notions of the ancient philosophers, and a tracing of the 

 steps by which the centrum theory has been gradually abandoned. The next six 

 chapters deal with various topics, among them the cause and distribution of 

 earthquakes, the nature of the shocks, the effect of earthquakes on surface and 

 underground water, and the earthquake faults and fissures and their relation to 

 earth lineaments. 



The latter topic, which is the author's special contribution, though touched 

 upon at various points in the book, receives special treatment in chapter vi. The 

 main points in this chapter are already familiar to American geologists from the 

 special articles by Professor Hobbs, and there has been a widespread dissent from 

 his views as to the relation between what he calls earth "lineaments" and seis- 

 motectonic lines. To the reviewer it seems that, while Professor Hobbs un- 

 doubtedly has a good point here, applied in moderation, he has given it a far 

 greater application than any facts he presents will warrant. There is much reason 

 to believe that many geologists have, in large measure, overlooked the significance 

 of joint planes, faults, and other lines of earth weakness in topographic expression; 

 and the facts presented by Professor Hobbs in this chapter, and in his special 

 articles, clearly show that there is a more definite and wide-spread relation between 

 earth lineaments and seismotectonic lines than has generally been recognized. 

 At the same time, it seems equally clear that Professor Hobbs has read into earth 

 lineaments a relationship to faults and fissures which no facts so far presented 

 will warrant. 



To be specific, selecting but one of a number of instances, the city of Elmira, 

 in central southern New York, is, according to Professor Hobbs, one of the greatest 

 centers of intersection of earth lineaments in northeastern United States, no less 

 than five lines centering there. Here, as in other maps, the data upon which 



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