Detrital Theory of Geology. 309 



of supply. If, furthermore, it is maintained, that the ocean 

 has within it springs of carbonate of lime, yet those springs 

 cannot have their source where granite is the bed ; for what 

 it contains in a very small proportion, it cannot supply in a 

 very large one. Hence, from whatever side it is viewed, 

 the lime contained in coral-reef, etc., cannot have its source 

 in or from granite. 



Another source of lime must not remain unnoticed 

 namely, the eruptive rocks that are not granite, for M. de 

 Beaumont has shown that these latter rocks have protruded 

 themselves through strata even later than the secondary, 

 upheaving, dislocating, and displacing their previously hori- 

 zontal beds or plains. 



As far as the eruptive rocks stand related to lime and 

 stratification generally, there is much difficulty in deciphering 

 their origin and effects, and they are closely connected with 

 the internal heat of the earth. The seething waves of liquid 

 fire, which, on approaching the crater of an active volcano, 

 can be distinctly heard, and which, after being long pent up, 

 pour forth their fiery streams as a devastating scourge upon 

 all around, bespeak the potency of the element at work, but, 

 like their own clouded light, leave us in ignorance as to the 

 extent of the hidden caldron, or its location in the bowels of 

 the earth. 



Though the heat beneath our feet increases by regular 

 increments, after a certain depth from the surface say, in 

 temperate regions, from 60 to 90 feet, and by calculation the 

 earth is proved to be in a state of fusion at a comparatively 

 short distance from the surface, yet the mean density of the 

 earth, as proved by the oscillations of the pendulum, forbids 

 the notion that the interior can be lighter than the crust, or 

 that the liquid lava poured out from a volcano can have the 

 same specific gravity within as on the surface, if it be liquid 

 at one fourth the semi-diameter of the earth, and that 



