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



distribution of active volcanoes about the seashores and by the 

 innumerable eruptions which occur in the depths of the ocean, 

 whereas such vents always die out inland ; and moreover by the fact 

 that of the vapors emitted from volcanoes 999 parts in 1,000 is 

 estimated to be steam, the remaining one-thousandth part being by- 

 products incidental to the moisture and high temperature. 



6. The vera causa of volcanic action and of certain earthquakes 

 thus established for some particular cases must be held to be the 

 universal cause in all cases whatsoever, according to Newton's rule 

 of philosophy. 



7. The heaving of steam accumulating within or just beneath 

 the earth's crust is therefore the true cause of all world-shaking 

 earthquakes, and volcanic outbreaks occur only when an outlet is 

 forced through to the surface, which usually happens in mountains, 

 where the earth's crust is already badly fractured and upheaved. 



8. When the subterranean steam pressure becomes great enough 

 to shake the earth's crust, it naturally moves at the nearest fault line, 

 where the rocks are broken, hut the movement observed is the result, 

 not the cause of the earthquake. 



9. Volcanoes are particular mountains blown open by steam 

 pressure under the throes of earthquakes (cracks in the rocks appear 

 to be the beginning of some few volcanoes), and since all volcanoes 

 blow out pumice and ashes, these materials must be held to exist 

 in all mountains, and are made by the inflation of molten rock with 

 steam and other vapors. 



10. Any mountain peak, therefore, is capable of becoming a 

 volcano if the subterranean steam pressure be sufficiently powerful 

 to break open an orifice. But orifices close up and volcanoes die 

 out inland and elsewhere if the supply of steam is inadequate to 

 keep open the vents upon which the activity depends. Even if 

 stopped up for a time later heaving of the earth may give the vol- 

 cano renewed activity, and when the mountain has been dormant 

 for a long time it is found that the violence of the eruption is greatly 

 increased. The violence of the subterranean pressure in such a case 

 approaches that of a region which has no vent at all, and hence we 

 see why earthquakes in non-volcanic regions frequently become so 

 terrible, because the forces accumulate to frightful fury before any 



