376 SEE— THE CAUSE OF EARTHQUAKES. Octobe 



which have had two, three, four or five cycles. Volcanoes are not local 

 phenomena, nor yet are they strictly universal. But they come very near 

 being universal. I think that Charles Darwin's observation that they are 

 associated with regions of elevation is very generally sustained, even in the 

 depths of the ocean." 



These remarks of Major Button, communicated to the writer in 

 a private letter, are of unusual interest. At the present time we 

 have no active volcano in the world more than lOO miles from the 

 sea or equivalent large body of water. It has been remarked that 

 Mt. Demavend is about 320 miles from the Mediterranean, but only 

 about 50 miles from the Caspian Sea, which is a deep body of salt 

 water. In the same way Jorullo in Mexico is about 80 miles from 

 the Pacific coast, but it has never been active since the first out- 

 break in 1759. Some of the volcanoes in the eastern range of the 

 Andes of Bolivia may be over 100 miles from the sea, but they are 

 much nearer Lake Titicaca and the terrible tropical rains which 

 constantly drench the eastern slopes of the Andes. 



Thus all active volcanoes, to the number of about 400, are very 

 near the sea or equivalent large lakes. In the interior of continents 

 they die out for lack of adequate ^water supply. Unfortunately, 

 we do not know the contours of the sea in past geological ages very 

 accurately, but from Major Button's remarks, quoted above, it seems 

 probable that volcanoes have always developed in the neighborhood 

 of the sea and died out when the water receded to a considerable 

 distance from them. This is well illustrated by the extinct volcanoes 

 now found in the western part of the United States. Thus volcanoes 

 of former ages seem to follow the same law as those now active. 



The present distribution of volcanoes proves conclusively that 

 they depend upon the sea. The erupting force is shown to be steam 

 by the great preponderance (999 parts in 1,000) which that vapor 

 has over all others. 



The progressive extinction of volcanoes in the interior of 

 continents is, therefore, clearly intelligible. Not only do the vol- 

 canoes die out for lack of motive power to keep open the orifices, 

 but the earthquakes also famish in the same way, though to a lesser 

 degree, because their explosive force is distributed over a wider 

 area and does not require to be so concentrated. Unless a volcano 

 keeps moderately active it becomes permanently closed by lava 



