276 SEE— THE CAUSE OF EARTHQUAKES. [October 19, 



completely bewildered by a multitude of unsatisfactory theories that 

 the progress of discovery itself is seriously embarrassed. 



There will naturally be those who doubt the existence of one 

 common and universal cause of earthquake and volcanic phenomena. 

 Nevertheless, difficult as the subject is, we believe that such a 

 cause exists, and that it is capable of demonstration, if not with 

 mathematical rigor at least with such high degree of probability^ 

 as to render the resulting theory practically useful, and we ask 

 nothing of the reader except a careful examination of the facts 

 as interpreted in the light of the cause assigned in this paper. 

 If such a view, associating the varied phenomena of earthquakes 

 and volcanoes, with mountain formation and the development of 

 great sea waves, under one common cause, renders them more intel- 

 ligible, and enables us to see the relations of all the observed phe- 

 nomena in a clearer and simpler light, there will be presumptive 

 evidence of the truth of the proposed theory ; and the probability of 

 its correctness will increase with the harmony existing among all 

 the known facts, and the effectiveness with which contradictions 

 of other theories may be established. The final test of the theory 

 will depend upon its usefulness in the advancement of discovery, 

 so as to harmonize the whole body of earthquake and volcanic 

 phenomena, including those associated with the origin and structure 

 of mountains, the observations of geodesy, and of great sea waves, 

 in their mutual relations, and in respect to the undisturbed parts 

 of our globe. If the theory shall meet this test satisfactorily, we may 

 feel confident that it assigns the true cause of the phenomena, and 

 within certain limits the resulting laws of nature may be used to 

 foretell events which will contribute to the repose and safety of 

 mankind, and to the progress and usefulness of discovery in this 

 interesting branch of natural philosophy. 



§ 2. The dynamical cause of earthquakes and volcanoes probably 



^ The unequivocal proof of the elevation of the coast at Yakutat Bay, 

 Alaska, Sept. 10-15, 1899, seems to remove the last trace of uncertainty re- 

 garding the chief function of earthquakes, and makes the demonstration as 

 rigorous as that of any theorem in geometry. See the important memoir of 

 Tarr and Martin, Bulletin of the Geological Society of America, vol. 17, May, 

 1906. Professor Georsre Davidson, President of the Seismological Society 

 of America, kindly called my attention to this classic work after the present 

 investigation was finished. Note added December 12, 1906. 



