SANDSTONE PETRIFACTIONS. 163 



has been commonly thought, made up of water- 

 worn or fractured pieces agglutinated by a basis. 

 I shall only observe, that one of the strongest of 

 these arguments appears to me to be the gradual 

 passage of the apparent fragments into the basis 

 by which they appear to be cemented ; and this, I 

 think, indeed, so strong, that scarcely any thing 

 more is wanted. But as abundance of evidence 

 can ,do no harm, I would take the liberty to 

 suggest, that the occurrence of petrifactions in 

 the situation of those I have before described, 

 seems to me to form an additional proof of the 

 correctness of Mr Jameson's opinion. I have at- 

 tempted to shew, that these appearances may be 

 accounted for on the hypothesis of sandstone being 

 a chemical deposition, but that they are quite inex- 

 plicable, on the supposition of its being a mechani- 

 cal formation. Now, the argument stands thus : 

 Sandstone petrifactions do occur ; but these cannot 

 have been formed mechanically. They must, there- 

 fore, have been formed chemically ; and hence sand- 

 stone has, in them at least, had a chemical origin. 

 But if it has had a chemical origin in one instance, 

 it may have had the same in another. 



The importance of the study of petrifactions will 

 not now be disputed. For as it was owing to the 

 observation of these in the strata in which they oc- 

 cur, that people were first led to speculate on the 

 manner on which these strata must have been form- 

 ed, (and hence our different Theories of the Earth,) 



L 3 



