642 MEUNIER:. THEORY OF VOLCANOES 



.thrusting :just described, whereby the rock masses are super- 

 posed (often in inverted order) acquires a new meaning from the 

 very presence of water. The water-soaked zone thus forms an 

 envelope around the deeper zone which is as yet too hot to ad- 

 mit the entrance of water. At many points the orogenic com- 

 pression, taking advantage of geoclases, carries hot waterless 

 strata over less hot water-soaked strata. The latter are thus 

 subjected to reheating under circumstances which are particu- 

 larly, interesting. We know the effects that are likely to be 

 produced by such reheating under the influence of water incor- 

 porated in deeply buried rock masses having no communication 

 with the surface. On this point Senarmont has made experi- 

 ments of which I am unable for lack of space to mention more 

 than the results. He has shown that in superheated water, as 

 .he called it, that is to say, water subjected to a temperature of 

 several hundred degrees in a closed vessel, the ordinary rocks 

 take on all the characters of metamorphic and volcanic rocks. 

 The water, strongly compressed and having reached the condi- 

 tion when it assumes the mineralizing function, becomes in- 

 corporated with the rock particles, and thus in the state of occlu- 

 sion it endows them with the expansive property. 

 '. Suppose next that a mass of rocks thus charged with occluded 

 water under high pressure is put into communication with 

 the atmosphere through a fissure, for example. The occluded 

 vapor, no longer held back by a resistance equal to its expansive 

 force, will seek to attain equilibrium of pressure with the atmos- 

 phere; it will issue from its confinement and carry with it the 

 rock magma in which it is dissolved, ejecting it through the 

 vent, and thus will produce the volcanic phenomenon in all its 

 details. Without attempting any detailed proof, let us note that 

 this line of reasoning explains all the incidents of the volcanic 

 phenomenon, from the ejection of ashes, vesicular pumice, and 

 scoriae to the rise and overflow of lava and even the formation 

 and reaction of fumaroles. 



: Volcanism as a whole, as has just been found to be the case 

 <with seismism, is an epiphenomenon of the production of moun- 

 tains. This is why intrusions of igneous rocks in all their forms 

 play such a prominent part in all complete mountain ranges. 



