i9o6.] ' SEE— THE CAUSE OF EARTHQUAKES. 391 



rocks is a fairly obvious indication of imprisoned vapors seeking 

 release from contact with molten rock. 



In fact nearly all the recent important earthquakes of great 

 violence, and inappropriately classed as tectonic, present strong 

 indications of being due to steam power. It probably is not too 

 much to say that it is doubtful if one of them could be fairly ex- 

 plained by mere subsidence due to the slipping of rock faults. 



In almost every case it will be found that the rock slipping 

 noted at the surface is small, while it is conceded that the chief 

 effect must depend upon great forces exerted from deep down. This 

 seems to be substantially admitted by most writers, who have a sus- 

 picion that the forces are singularly deep-seated and otherwise act 

 in a strange way. The Charleston earthquake originated twelve 

 miles below the surface, while the San Francisco earthquake will 

 not prove to be of less depth. The Bengal-Assam earthquake of 

 June 12, 1897, investigated by Mr. R. D. Oldham, must have had 

 great depth, owing to the wide extent of country over which is was 

 felt and the great intensity of the shocks. The same is true of the 

 Mino-Owari earthquake of October 18, 1891, and all other earth- 

 quakes of high intensity which were widely felt. The Valparaiso 

 earthquake of August 16, 1906, was among the most terrible of 

 modern times, and it was so widely felt that the depth could hardly 

 be less than fifteen or twenty miles. 



It seems desirable to direct attention to the fact that probably 

 not one of these great earthquakes has occurred in a region where 

 seeping of water and formation of steam may not have been the 

 dynamic cause. The center of the violent Bengal-Assam earthquake 

 was under the great Bramaputra River, where it spreads to great 

 width and drains an immense volume of water from the Himalayas. 

 This region was originally a deep trough in the sea and has since 

 been filled in ; and owing to the great surface drainage is still 

 essentially an inland sea not far from the Bay of Bengal, which 

 receives also the Ganges as well as the Bramaputra. The situation 

 is very similar to that of New Madrid, but is nearer the sea, and 

 has the Himalayas on the north, from which the drainage is enor- 

 mous. Besides there is in that region a natural survival of the forces 

 which uplifted the Himalayas, and this ancient sea valley did most 

 of the work involved in the raising of these mighty mountains. 



PROC. AMER. PHIL. SOC., XLV. 184 Y, PRINTED FEBRUARY 25, I907. 



