igoS.] THE PHYSICS OF THE EARTH. 163 



eminent of living physicists. While disclaiming especial authority 

 to pass upon such a question, they expressed the opinion that it was 

 very improbable that the ocean bottom could be water-tight, unless 

 the nature of the rock was greatly modified by pressure, which could 

 hardly be the case in the first twenty miles of the earth's crust, where 

 the pressure does not exceed 8,600 atmospheres. 



Whatever doubt might attach to this solution of the problem, 

 from an experimental standpoint, where positive knowledge is greatly 

 lacking, seems to be dispelled by the phenomena noticed in the 

 sea bottom in various places, which show that lava is expelled from 

 beneath the sea and pushed under the adjacent land. The phe- 

 nomena noticed in the laboratory of nature thus prove the leakage 

 of the ocean from an observational standpoint, because they admit 

 of no other interpretation. 



§ 3. The Theory of Water-tightness of the Ocean Bottoms Dis- 

 proved by the Expulsion of Lava from under the Sea. — Just south 

 of the Aleutian Islands, a long, narrow and deep trench just parallel 

 to this chain has been dug out by the expulsion of lava from beneath 

 the Sea. The nature of this trough is illustrated by the accompanying 

 Map. 



It will be seen that the island chain adjacent to the trough dug 

 out in the sea bottom is really a mountain range under water, with 

 only occasional peaks projecting above the water as islands. In 

 fact the Aleutian Islands are a continuation of the Alaskan Moun- 

 tains which are part of the Rocky Mountain System, and the range 

 here continues into the sea. If therefore the Aleutian Islands are 

 mountains now in process of formation in the sea, it would seem to 

 follow logically that the Rocky Mountains and Andes, from Alaska 

 to the straits of Magellan, were formed in the same way. What 

 then is the process at work forming the Aleutian Islands ? 



It is evident that the deep trench south of the islands has been 

 dug out by the expulsion of lava from under the sea and its injec- 

 tion under the Aleutian ridge; this is accomplished by earthquakes, 

 and the process is still in full operation at the present time. This 

 region is a well-known breeding-ground for world-shaking earth- 

 quakes and seismic sea waves. Several islands have been uplifted 

 since 1783, and one or more new volcanoes have broken out within 



