X907.] AND MOUNTAIN FORMATION. 371 



recognized by investigators that the most active region of seismic 

 disturbances is along the Aleutian, Kurile, and Japanese Islands, and 

 in the East Indies. Major Button not only speaks of the tremend- 

 ous power of the mighty earthquakes in this region, but also calls 

 attention to the prevalence of seismic sea waves following the earth- 

 quakes. " The profound depths of the ocean just off the eastern 

 part of the Aleutian chain is one of the great breeding-grounds of 

 world-shakers. A rather small basin in the ocean-bottom has here 

 a depth of nearly four thousand fathoms, and the descent to it is by a 

 long and strong gradient." (" Earthquakes in the Light of the 

 New Seismology," p. 258.) 



In the Bakerian Lecture to the Royal Society, 1906, Professor 

 Milne treats of great earthquakes and says that " the most active 

 district is at present that of the East Indies." But he also points 

 out the great activity of the region along the Japanese and Aleutian 

 Islands, where the sea is very deep. 



Let us now examine the topographic map of the sea-bottom near 

 the Aleutian Islands, as given in the Coast Survey Report for 1900, 

 Appendix No. 7 (" Manual of Tides," Part IV., A, " Outlines of 

 Tidal Theory," by Rollin A. Harris). We notice that along the 

 Aleutian Islands the sea-bottom is sunk down into a narrow trough, 

 which for a considerable distance is over 4,000 fathoms deep, and 

 exactly parallel to the chain of islands. The length of this trough 

 is found to be from thirty to thirty-three times its breadth; and 

 the deeper part is only a continuation of the depression of the 

 shallower. This is shown by the way in which the two troughs, 

 with depths of 4,000 and 3,000 fathoms respectively, fit together, as 

 if one were placed within the other. Moreover the chain of islands 

 is seen to be merely the highest peaks of a mountain range rising 

 just parallel to this deep trough. This range also is about 33 times 

 longer than it is broad, so that if the elevation were shoveled off 

 and thrown into the trough, it would just about fill up the depression, 

 and leave the surrounding sea bottom of nearly uniform depth. By 

 the same method of calculation which was employed in the paper 

 on the cause of earthquakes (p. 311), it may be shown that the 

 probability of this parallelism occurring without a physical basis is 



