meunier: theory of volcanoes 643 



Summarizing, we may say that eruption results from the collab- 

 oration of two processes, seemingly quite unrelated : 



1 . The progressive penetration of water and other volatile sub- 

 stances to a depth within the earth's crust which is strictly depend- 

 ent at every instant on the degree of spontaneous cooling; 



2. The tangential compression of the rocks, due to the contrac- 

 tion of the nucleus and also to the tendency of the crust to 

 founder into deeper and deeper regions where the horizontal 

 sp£ ce grows narrower and narrower. 



Thus the crust of our planet forms a kind of weaver's loom, 

 producing the volcanic tissue, the warp being represented by the 

 descending network of threads of water, while the woof is repre- 

 sented by the tangential network of heated material, due to the 

 orogenic superposition of intrusive masses over water-soaked 

 sediments. 



Harking back to the point from which we started, we may 

 here adopt the practice of the mathematician who devotes him- 

 self to the discussion of a given problem. We may inquire what 

 special results would follow from modifying one or the other 

 of the two factors of the eruptive phenomenon. 



Let us note, first of all, that the volcanic phenomenon could 

 only have appeared after a long evolution of the terrestrial 

 globe, because it requires a crust, and not only this but the super- 

 position of two concentric zones: the one deep down and very 

 hot, the other at less depth, impregnated with water and of 

 moderate temperature. 



However, to dwell on this point would be to enter into the 

 domain of comparative geology. Suffice it to say that from the 

 moment when the crust was formed, and long before, eruptions 

 had taken place, different no doubt from, but yet comparable in 

 certain respects and belonging to, the class now represented by 

 the majestic spectacle of the solar eruptions. 



Herve Faye recently established the synthetic theory of the 

 sunspots and of the red protuberances accompanying them, and 

 showed that these phenomena represent an incessant radial 

 circulation of the material constituting the epidermic zone of the 

 sun; we might almost say the cortical zone, for the photosphere 



