BY COMPRESSION, OKJJ 



eanic streams, applies equally to that deeper and more general vations on the 

 heat by which the lavas' themselves are melted and propelled extent of the 



upwards. That they have been really so propelled, from a heat which is 



, "r . ,. . , ^ . , . known to act in 



great mternal mass or matter, m liquid fusion, seems to admit the interior of 



of no doubt, to whatever cause we ascribe the heat of volcanoes, our globe. 

 It is no less obvious, that the temperature of that liquid must 

 be of far greater intensity than the lavas, flowing from it, can 

 retain when they reach the surface. Independently of any 

 actual eruption, the body of heat contained in this vast mass of 

 liquid, must diffuse itself through the surrounding substances, the 

 intensity of the heat being diminished by slow gradations, in 

 proportion to the distance to which it penetrates. When, by 

 means of this progressive diffusion, the heat has reached an as- 

 semblage of loose marine deposites, subject to the pressure of a 

 great superincumbent weight, the whole must be agglutinated into 

 a mass, the solidity of which will vary with the chemical com- 

 position of the substance, and with the degree of heat to which, 

 each particular spot has thus been exposed. At the same time, 

 iinalogy leads us to suppose, that this deep and extensive heat 

 must be subject to vicissitudes and intermissions, like the exter- 

 nal phenomena of volcanoes. We have endeavoured to ex- 

 plain some of these irregularities, and a similar reasoning may be 

 extended to the present case. Having shewn, that small in- 

 ternal streams of lava tend successively to pervade every weak 

 part of a volcanic mountain, we are led to conceive, that the 

 great masses of heated matter just mentioned, will be successive- 

 ly directed to different parts of the earth ; so that every loose 

 assemblage of matter, lying in a submarine and subterranean 

 situation, will, in its turn, be affected by the indurating cause; 

 and the influence of internal volcanic heat will thus be circum- 

 scribed within no limits but those of the globe itself. 



A series of undoubted facts prove, that all our strata once All our strata 

 lay in a situation similar in all i-espects to that in which the jje^^j ^jj^ seaT 

 inarine deposites just mentioned have been supposed to lie. 



The inhabitant of an unbroken plain, or of a country formed 

 of horizontal strata, whose observations have been confined 

 to his native spot, can form no idea of those truths, which at 

 every step in an alpine district force thfMnselves on the mind 

 of a g;cological observer. Unfortunately for the progress of 

 geology, both London and Paris, are placed in countries of little 



interest j 



