Effects of Heat ynodified hy Compression^ 14S 



II. That during the action of heat all these rocks (even 

 such as now appear at the surface) lay covered by a superin- 

 cumbent mass, of great weight and strength. 



III. That in consequence of the combined action of heat 

 and pressure, effects were produced dlfi'erent from those of 

 heat on common occasions ; in particular, that the carbonate 

 of lime was reduced to a state of fusion, more or less com- 

 plete, without any calcination. 



The essential and characteristic principle of his tlieory is 

 thus comprised in the word compression ; and by one bold 

 hypothesis, founded on this principle, he undertook to meet 

 ;dl the objections to the action of fire, and to account ibr 

 those circumstances in which minerals are found to differ 

 'from the usual products of our furnaces. 



This system, however, involves so many suppositions, 

 apparently in contradiction to common experience, which 

 meet us on the very threshold, that most men have hitherto 

 been deterred from the investigation of its principles, and 

 only a few individuals have justly appreciated its merits. It 

 was long before I belonged to the latter class j for I must 

 own that, on reading Dr. button's first geological publica- 

 tion, I was induced to reject his system entirely, and should 

 probably have continued still to do so, with the great ma- 

 jority of the world, but for my habits of intimacy with the 

 author; the vivacity and perspicuity of whose conversation 

 formed a striking contrast to the obscurity of his writings. 

 1 was induced by that charm, and by the numerous original 

 facts which his system had led him to observe, to listen to 

 his arguments in favour of opinions which I then looked 

 upon as visionary. I thus derived from his conversation the 

 same advantage which the world has lately done from the 

 publication of Mr. F^layfair's Illustrations ; and experienced 

 the same influence which is now exerted by that work on the 

 minds of our most eminent men of science. 



After three years of almost daily warfare with Dr. ITutton, 

 on the subject of his theory, I began to view bis funda- 

 mental principles with less and less repugnance. There is a 

 period, I believe, in all scicfilific investigations, when the 

 conjectures of genius cease to appear extravagant, and when 

 4 ve 



