CONTORTIONS OF ROCKS. l2i 



the facts that relate to their situation or connexions^ 

 are likely to bear on this question. 



It may be remarked in the first place, that the chief 

 curvatures take place in the most antient strata; and, 

 in these, it is observed that their positions are not 

 those which they must have originally possessed, if, 

 as is supposed, they have been deposited at first from 

 water. Yet we must be cautious not to make a rule 

 from this observation ; as has been done for the sup- 

 port of a theory, by writers who ought to have been 

 well aware of the injury done to a cause by an inap- 

 plicable argument. The secondary strata are some- 

 times elevated to the vertical angle without curvature. 



It is next well known, that curvatures of the strata, 

 and even considerable contortions, occur in the vicinity 

 of trap and granite; while the phenomena by which 

 they are attended, prove that the derangement of the 

 one corresponds to the position of the other. What- 

 ever value may attach to this well known-fact, in the 

 following arguments, it must at the same time be 

 added, that innumerable instances of curvature occur, 

 where the presence of these intruding rocks cannot be 

 discovered. 



Of the Causes of Flexures and Contortions. 



It remains now to inquire into the causes of these 

 phenomena, which, it must be very apparent, are of 

 high importance in every investigation that has for its 

 object a legitimate theory of the earth. 



In the first place, it is proper to ascertain whether 

 the strata may not originally have possessed this form, 

 whatever theory may be received respecting their 

 origin. It may be admitted without much hesitation, 



