228 EARTHQUAKES. 



boundaries of the Pacific ocean. It may be remarked 

 that these boundaries slope beneath the neighbouring 

 ocean at a much steeper angle than the boundaries of 

 countries where earthquakes occur but seldom. The 

 coasts of South America, Kamschatka, the Kuriles, Japan, 

 and the Sandwich Islands, for example, have slopes beneath 

 the Pacific from one in twenty to one in thirty. The 

 coasts of Australia, Scandinavia, and the eastern parts of 

 South America, where earthquakes are practically un- 

 known, have slopes from one in fifty to one in two 

 hundred and fifty. Many earthquakes have taken place 

 in mid-ocean. In the Atlantic Ocean M. Perrey has 

 given about 140 instances of such occurrences. 



The majority of the earthquakes which shake Japan 

 appear to have their origin in the neighbouring ocean. 

 If we could draw a map of earthquake origins, it is prob- 

 able that the greater number of the marks indicating 

 these origins would be found to be suboceanic and along 

 lines parallel to the shores of continents and islands 

 which rise steeply from the bed of deep oceans. In 

 countries like Switzerland and India, our marks would 

 hold a relationship to the mountains of these countries.^ 

 liOoking at the broad features of the globe, we see on its 

 surface many vast depressions. Some of these saucer-like 

 hollows form land surfaces, as in central Asia. The 

 majority of these, however, are occupied by the oceans. 

 Active volcanoes chiefly occur near the rim of the hollows 

 which have the steepest slopes. The majority of earth- 

 quakes probably have their origin on or near the bottom 

 of these slopes. To these, however, there are exceptions, 

 as for instance the earthquakes in the Alps, in the hills of 



* David Milne says that 'out of 110 shocks recorded in England, 

 thirty-one originated in Wales, thirty-one along the south coast of 

 England, fourteen on the borders of Yorkshire and Derbyshire, and five 

 or six in Cumberland.' 



