SANDSTONE PETRIFACTIONS. 165 



first observed, — and the observation is of the utmost 

 importance, — that different petrifactions characterise 

 different Formations. 



But on this subject I shall not at present enlarge, 

 as I may, perhaps, at a future period, trouble the 

 society with some observations on it in a different 

 shape. 



Cuvieii has done much in this department, and 

 apparently without knowing what Werner had done 

 before him. He has demonstrated, not only that, 

 without the existence of petrifactions or extraneous 

 fossils, we never could have known, or in all proba- 

 bility never would have suspected, that there were 

 successive formations or depositions of the strata and 

 other enormous masses which compose the crust of 

 the Globe ; but that by observing these, we pursue 

 the track which is alone likely to conduct us to a 

 knowledge of the causes of these depositions : Or 

 rather (in more precise language, perhaps), which is 

 likely to lead us to the knowledge of the real order 

 of their succession. 



It is his opinion, however, that other causes be- 

 sides those which we at present observe to operate 

 in nature, must have then existed. But this is evi- 

 dently giving up the question ; it evidently amounts 

 to the assertion, That the laws of the physical world 

 were formerly different from what they now are. 

 And if so, then I am afraid we never can under- 

 stand how these laws operated. It is the same 

 thing as to tell us, that petrifactions were formed, we 



