234 



CAUSES OF PERMANENT ELEVATION [Ch. XXXIII 



mucli 



volcanic openings. That tliere shonld be so 

 cliemical action and reaction, developed in certain parts of 

 the interior of the earth, is not so wonderful as the ordinary 

 repose and inertness of the internal mass. When we con- 

 sider the combustible nature of the elements of the earth, so 



to ns — the facility with which their 



known 



compounds may be decomposed and made to enter into new 

 combinations — the quantity of heat which, they evolve 

 during these processes; when we recollect the expansive 

 power of steam, and that Avater itself is composed of two 

 gases which, by their union, produce intense heat ; when we 

 call to mind the number of explosive and detonating com- 

 pounds which have been already discovered, we may be 



ishment of Pliny, that £ 

 general conflagration : 



' Excedit 



should pass without a 



profecto omnia miracula, uUuni diem fuisse quo non cuncta 



conflagrarent.' ^ 



But the difficulties we encounter when we attempt to form 

 a chemical theory of volcanos, are almost insurmountable, in 

 consequence of our inability to test experimentally the mode 

 in which different substances, solid, fluid, or gaseous, would 

 behave under conditions of pressure and temperature wholly 

 different from those experienced at the surface. A simple 

 difference in the amount of heat may, observes Sa^mann, 



modified. Mer 



1 affinities of bodies to be essentially 

 le remarks, ^does not combine with 

 oxygen at ordinary temperatures, but combines Avith it at its 

 boiling point, and then gives it off again at an incipient red 

 heat. Here we have three different states of chemical affinity 

 within the limits of a few hundred degrees ; and Avho would 

 dare assert, that at this last phase of separation, the chemical 

 action between these two elements ceases definitely and for 



3S? But what is true of mercury and 



all higher temperatures? 



oxygen, is likewise true for all other elements.'f 



Causes of permanent elevationand subsidence of 



position of the fossiliferous and other rocks in the earth's 



The 



^ Hist. Mimdi, lib. ii. c. 107. 



t Louis Ssemann, Notes on Daubree on Meteorites, Geol. Mag. 1SG6, p. 362. 



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