374 MINERALOGICAL OBSERVATIONS 



those decayed and half- rotten trees, with which 

 we now find them to abound. 



Something, therefore, it was necessary to de^ 

 vise, in order to afford at least a plausible expla- 

 nation of the above and other similar phenomena. 

 Theories in abundance, have been from time to 

 time proposed, and have all had their day of vogue 

 and admiration. But how few of them have been 

 any thing else than mere fancies, or hypotheses pro- 

 ceeding on by far too narrow an induction of parti- 

 culars. Indeed, it would not be going too far to 

 say, that the greater part of them have been purely 

 gratuitous suppositions. What else can well be 

 affirmed of the celebrated theories of Burnet, 

 Buff ON, and many others ? 



The subject is abstruse and difficult, and the 

 theorists have been adventurous. We are still 

 probably very far from a true theory of the 

 earth, or a knowledge of the real cause or causes 

 of geological phenomena. Nor is it very un- 

 likely, that this knowledge may for ever elude 

 our research, and that we may seek in vain for 

 the actual manner in which the internal structure 

 of our planet was produced. The bodies about 

 which we reason, are in most cases concealed from 

 our view ; and it is only incidental glimpses of 

 them, as it were, that we are able to obtain. It 

 is only where the sea, or rivers, or mines, or quar- 

 ries, have laid bare the rocks ; or where they are 

 naturally exposed on the brows of mountains,, in 



