308 SEE- THE CAUSE OF EARTHQUAKES. [October 19, 



the Cordilleras. And it is natural that in this upheaval of the 

 crust, release of strain due to subterranean steam pressure should 

 occasionally come by the throwing up of cross ridges, sometimes 

 enclosing undrained areas, and thus lakes like Titicaca are formed. 

 Proceeding upon this simple and natural principle, we may easily 

 explain all the chief characteristics of the Andes. It is impossible 

 to doubt that these mountains have been formed by the very forces 

 which we see still at work there. The upheavals have been step by 

 step, and earthquakes forcing up the mountains have at the same 

 time caused the ejection, by the pushing along of a column or rather 

 a layer, of the necessary matter from under the sea, thus sinking the 

 bottom into a permanent trough, while the subsidences accompany- 

 ing some of the earthquakes have produced enormous sea waves. 

 Countless thousands and perhaps millions of these earthquakes and 

 sea waves have occurred throughout past geological ages. 



The trough parallel to the coast and the upheavals and sea 

 waves now observed are a survival to show us just how the moun- 

 tains have been formed, and where the next mountain range will 

 form in the sea. We can predict the formation of the new Andes as 

 confidently as we can an eclipse, though it will be a much longer time 

 before the new mountains develop ; for we recognize the cause to be 

 a true one, and see just how it works by a kind of self-regulating 

 automatic process. The working of the cause has been observed 

 near Mt. Pelee, and the operation of the same process along the 

 South American coast is proved by the observations of Charles Dar- 

 win and by the great sea waves frequently observed within historical 

 times. 



§ 15. Investigation of the significance of the observed lay of 

 mountain chains by means of the theory of probability. 



In their new work on ''Geology," Vol. I (p. 543), Chamberlin 

 and Salisbury remark that the relationship between the direction of 

 folded ranges of mountains and the adjacent seacoast is '' a coinci- 

 dence that is only in part causal/' There are, doubtless, many ways 

 in which this problem could be treated by the methods employed in 

 theory of probability. Without claiming to exhaust the various lines 

 along which the discussion might be developed, we believe the fol- 

 lowing method rests on equitable considerations. 



