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



Moreover, the cause of the great sea waves was now perfectly 

 clear. It was impossible to doubt that these phenomena, of the 

 class in which the water recedes from the shore in the first few 

 minutes following an earthquake, generally arise from a subsidence 

 of the sea bottom after the expulsion of porous lava in the natural 

 process of elevating the mountains and coasts. 



After these ideas had been worked out in such a way as to es- 

 tablish harmony among the widely diversified phenomena it was 

 gratifying to find that such views were not inconsistent with the 

 thoughtful remarks of Humboldt, and that Charles Darwin seventy 

 years before had reached conclusions in most respects remarkably 

 similar. It seemed, therefore, justifiable to suppose that the process 

 of mountain formation thus outlined and verified was in all proba- 

 bility the correct one. Such was the order of the writer's thought, 

 which he records with reluctance and hesitation, but chiefly in the 

 hope that it may not be wholly without value to others. 



In the final arrangement of the paper it was deemed best to intro- 

 duce the citations from Humboldt and Darwin under the discussion 

 of the several topics rather than as extremely long foot-notes. And 

 this arrangement was the more agreeable on account of the great 

 esteem in which the writer has always held these illustrious investi- 

 gators. As Professor Milne is justly recognized to be the most 

 eminent living authority on earthquakes, to whom we owe extensive 

 international cooperation and the present widespread interest in the 

 subject, which has contributed so greatly to the advancement of our 

 knowledge, the same principle has naturally been employed in the 

 exposition of the results of his researches. 



While it is impossible to estimate too highly the great strides 

 recently made in seismology under the leadership of Professor 

 Milne, Dr. Davidson, Montessus de Ballore, Major Dutton, Von 

 Rebeur-Paschwitz, Dr. Agamennone, Dr. Rudolph, Professor 

 Omori, and others, who have reduced seismology to a science of 

 precise observation and measurement, it is perhaps unfortunate that 

 the views of Humboldt and Charles Darwin as to the causes involved 

 in earthquakes were ever abandoned by modern investigators, though 

 this probably has not retarded the progress of observation and 

 experimentation on the constitution of the globe. 



