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



others, which are of great value for the close study of particular 

 regions, we may call attention to the conclusions of Milne, and 

 Montessus de Ballore regarding the slope of the seashores as im- 

 portant factors in the development of earthquakes. 



As a result of careful study of Japanese earthquakes covering 

 eight years. Professor Milne found that '' the central portions of 

 Japan where there are a considerable number of active volcanoes 

 are singularly free from earthquakes. The greater number of dis- 

 turbances originate along the eastern coast of the Empire and many 

 of them have a submarine origin." " Lines 120 geographical miles 

 in extent in running in an easterly or southeasterly direction from 

 the highlands of Japan into the Pacific Ocean, like similar lines 

 drawn from the Andes westwards into the same ocean, have a slope 

 of I in 20, or i in 30, and in both of these districts earthquakes are 

 frequent. On the contrary, along the faces of flexures which are 

 comparatively gentle, being less than half of these amounts, which 

 may be seen along the borders of most of the continents and islands 

 of the world, earthquakes are comparatively rare. The inference is 

 that where there is the greatest bending it is there that sudden 

 yielding is most frequent."^ 



It seems advisable to quote more at length the full line of thought 

 laid down by Professor Milne in his classic work on " Seismology " 

 (London, 1898). On page 31 Professor Milne says: 



"A very much more serious objection to the volcanic origin of the 

 majority of earthquakes is the fact that these disturbances are common in 

 the Himalaj^a, Switzerland, and other non-volcanic regions. The destructive 

 earthquake in 1891 in Mino and Owari occurred in a region of metamor- 

 phic and stratified rocks. Again, an analysis of some ten thousand earth- 

 quake observations of Japan shows that there have been but comparatively 

 few which had their origin near to the volcanoes in the country. The 

 greater number of this series originated beneath the ocean or along the 

 seaboard, and as they radiated inland they became more and more feeble, 

 until, on reaching the backbone of the country, which is drilled by numerous 

 volcanic vents, they were almost imperceptible. Beyond this central range 

 of mountains, earthquakes are only rarely experienced, and what is true of 

 Japan seems to be generally true for the coasts of North and South America." 



" Throughout the world we find that seismic energy is most marked 

 along the steeper flexures in the earth's crust, in localities where there is 

 evidence of secular movement, and in mountains which are geologically new 



^ Cf. Seismological Journal of Japan, 1895. p. xv; and Dutton, "Earth- 

 quakes in the Light of the New Seismology," chapter III. 



