ill 



CHAP. IX. 



On the Flexures and Contortions of Rocks. 



As THE fractures and dislocations of strata give rise 

 to important deductions with regard to the changes 

 which have taken place in the superficial portions of 

 the earth since their deposition, so, hy their flexures 

 and contortions, we are led to form interesting con- 

 clusions respecting the original condition of these 

 deposits, or the changes which they may have expe- 

 rienced after their formation. 



Instances of the contortion and flexure of strata 

 have been observed in every part of the world, and 

 they will be found recorded in the writings of nume- 

 rous authors ; of those who have had a theory to 

 support, and of those who profess to be alike indif- 

 ferent to all. I have without scruple associated toge- 

 ther both these modifications of curvature ; not how- 

 ever without being aware that some writers have made 

 distinctions, and have deduced separate arguments for 

 their particular purposes, from each. It appears to 

 me that some of these have been warped by the par- 

 ticular bias of the writers ; but such distinctions as 

 seem to be essential, or to involve interesting cir- 

 cumstances, will be pointed out wherever it is thought 

 necessary. 



Of Flexures. 



The simplest species of flexure is that which re- 

 sembles the marks left by the retiring sea on sandy 



