302 SEE-THE CAUSE OF EARTHQUAKES. [October 19. 



deepest oceans; but volcanoes would develop chiefly in certain 

 regions where the rocks are already broken in the uplift of moun- 

 tains and therefore easily burst open, whereas earthquakes might 

 occur in any locality where the leakage of the sea developed suffi- 

 cient steam. It is undeniable that this is in accordance with obser- 

 vation on our actual earth ; and it shows that while both volcanoes 

 and earthquakes should surround the Pacific Ocean, earthquakes 

 are much more widely and uniformly distributed than volcanoes. 

 Also in those regions near actual volcanoes, where the imprisoned 

 steam has a vent, violent earthquakes should not occur; but if the 

 activity of the volcano ceases, the danger of earthquakes would be 

 increased. 



Humboldt remarks that this opinion was widely spread among 

 the people of the Andes, and it would be difficult to deny that this 

 result of their long experience was well founded, though confessedly 

 they did not know upon what principle the dreaded explosions 

 depended. 



If the leakage from the sea has moderate uniformity with respect 

 to the time, it is clear that the cessation of the smoke of a volcano 

 is really one of nature's danger signals, since the pressure within 

 the subterranean reservoirs of the mountain and adjacent regions 

 may then increase to such a degree as to become extremely dan- 

 gerous. Neither Krakatoa nor Pelee had been active for long 

 periods before the fearful explosions of 1883 and 1902. Krakatoa 

 had been practically dormant for two hundred years, and while 

 Pelee had experienced an eruption in 1851, it was small, and no 

 important explosion had occurred since 1762.^ In the case of Ve- 

 suvius the general experience is the same — the longer the eruptions 

 are delayed the more violent they become. For it appears that in 

 79 A. D. no eruption had occurred for about six centuries, and 

 Pliny's description of that outbreak shows that it was more violent 

 than any that has occurred since. The volcano of Conseguina in 

 Central America illustrates the same principle by the long repose 

 preceding the frightful eruption of 1835, which spread devastation 

 far and wide, and in many ways resembled the terrible outbreak of 



' Cf. Heilprin, " Mont Pelee and the Tragedy of Martinique," pp. 61-187, 

 188. 



