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, by 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 he 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 he pointed out wherever it is thought necessary. Of Flexures. The simplest species of flexure is that which re sembles the marks left hv the retiring sea on sandy