1.24 TRANSACTIONS iSgg-'oO 



more than fifty miles in length which carried mountain ranges 

 several thousands of feet in height was suddenly fissured alcng its 

 length ; accompanying this there was a back spring of strata re- 

 leased from strain and a collapse by falling of a valley bottom and 

 its bounding ridges. The magnitude of this impulse, received 

 almost simultaneously over a large area, caused Central Japan to 

 shake so violently that forests slipped down from mountain sides 

 to block up valleys, while earth waves were created which travell- 

 ed round the globe." 



It is undoubtedly true that earthquake disturbances are not 

 generally accompanied by any visible fracturing on the surface of 

 the ground; but that they may be the result of such fracturing is 

 rendered probable by the fact that they occur in regions where 

 secular movements are in progress, or at least where geological ex- 

 perience has demonstrated that dislocations are numerous. 



Professor Milne remarks that throughout the world 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, and where we have 

 no reason for supposing that Brady seismic movements have yet 

 ceased. 



As examples of the flexures to which reference is made, tak- 

 ing sections running at right angles to the coast lines of the var- 

 ious continents, it is found that, taking 120 geographical miles as 

 the unit of distance, on the west coast of South America they 

 slope I in 20.2 



The Kuriles from Urup i in 22.1 



Japan, W coast of Nipon i in. 30.4 



Sandwich Islands, northwards i in 23.5 



Australia generally i in 91 



Scotland from Ben Nevis i in 158 



South Norway i in 73 • 



South America, eastward i in 243 



The conclusion he arrives at from this is, that if we find slopes 

 of considerable length extending downwards beneath the ocean, 

 »teeper than i in 35, in such places sub-marine earthquakes with 

 their accompanying landslips may be expected. On the summit 

 of these slopes, whether they terminate in a plateau or as a range 



