74 EFFECT'S of HEAT 



refting problems that has ever engaged the attention of men of 

 fcience. 



He fuppofed, 



I. That Heat has acted, at fome remote period, on all 

 rocks. 



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

 fiich as now appear at the furface) lay covered by a fuper in- 

 cumbent mafs, of great weight and strength. 



III. That in confequence of the combined action of Heat 

 and PrefTure, effects were produced different from thofe of heat 

 on common occasions; in particular, that the carbonate of 

 lime was reduced to a ftate of fufion, more or lefs complete, 

 without any calcination. 



The eflential and characteristic principle of his theory is thus 

 comprifed in the word Comprejfion; and by one bold hypothecs, 

 founded on this principle, he undertook to meet all the objec- 

 tions to the action of fire, and to account for thofe circum- 

 stances in which minerals are found to differ from the ufual 

 products of our furnaces. 



This fyftem, however, involves fo many fuppofitions, appa- 

 rently in contradiction to common experience, which meet us on 

 the very threfhold, that molt men have hitherto been deterred 

 from the inveftigation of its principles, and only a few indivi- 

 duals have juftly appreciated its merits. It was long before 

 I belonged to the latter clafs \ for I mufl own, that, on read- 

 ing Dr Hutton's first geological publication, I was induced to 

 reject his fyftem entirely, and mould probably have continued 

 still to do fo, with the great majority of the world, but for my 

 habits of intimacy with the author ; the vivacity and perfpicui- 

 ty of whofe converfation, formed a striking contrast to the ob- 



fcurity 



