CENTRAL HEAT. 



575 



tense, that such sedimentary masses should be first elevated into vertical positions, and 

 then overturned, or bent hack upon their axes ? 



The mere announcement of these grand changes gives us a full perception of the mag- 

 nitude of the scale and power of the forces employed ; and we see in them a cause fully 

 adequate to account satisfactorily for many of the results described under the head of 

 drifted materials. 



In the ensuing chapter we shah take into consideration the equally wonderful zoolo- 

 gical phenomenon of the coexistence of similar species of animals in the most distant 

 quarters of the globe. 



In concluding the first part of this volume, or that which embraces descriptive geo- 

 logy, we would observe, that abundant proofs have been adduced to show, that the forces 

 employed in dislocating the crust of the globe were of extraordinary intensity. These 

 well-registered phenomena are, we contend, absolutely inexplicable without the inter- 

 vention of paroxysms infinitely greater than any of which modern times furnish 

 examples ; — and yet we shall find, that such data, though drawn from the opposite 

 extremes of the subject, are not in collision, and will not impede the onward march of 

 our science. 



Judging from the facts before them, geologists are entitled to look to a deep-seated 

 and widely extended explanatory cause ; and hence many have been led to believe, 

 that all the ancient phenomena proving outburst and dislocation, have proceeded from 

 a central heat, of which the volcanic ebullitions of past periods and the present are 

 merely the external signs. Now, if the astronomer has correctly supposed that this 

 planet was originally a semifluid mass, which by revolving on its axis assumed a sphe- 

 roidal form ; the geologist, examining into the nature of the oldest crystalline rocks, 

 sees in them the clearest evidence of the effects of intense heat, which bursting out at 

 intervals through sedimentary deposits, evolved the sheets of matter which constitute the 

 axes and centres of many mountain chains. He infers that central heat has subsequently 

 been the source and great agent of the mutations he traces 1 , not only from the surpassing 

 grandeur of the phenomena, but also because they harmonize with the probable relative 

 conditions of such periods ; for each succeeding accumulation of fresh sedimentary 

 matter would, as before hinted, necessarily tend to repress the power of heat proceeding 

 from within, whether in the form of actual molten matter or of gas and steam. Each 

 great igneous eruption, carrying with it fresh materials for additional deposits to be 

 spread out on the bed of the ocean, would in fact be auxiliary to the repression of 

 similar eruptions in future, by adding new folds to the pre-existing crust which enveloped 

 the central and heated nucleus. 



The question therefore is, does Nature teach us, that the most violent dislocations are 

 apparent in our geological phenomena ? If (as I firmly believe) she does, and further 

 impresses on us the belief of a former state of paroxysmal turbulence and chemical 



1 See the powerful essays of Cordier and Fourrier. 



