CONTORTIONS OF ROCKS. 125 



That strata may be bent by fire, we have hourly 

 evidence in the phenomena that take place in furnaces 

 and limekilns, where schistose rocks have been ex- 

 posed to heat. In the vitrified forts of Scotland, the 

 micaceous schists which have been subjected, appa- 

 rently, to the long-continued action of a moderate heat, 

 and to the various pressure of the surrounding ma- 

 terials, are often bent, with little loss of their natural 

 characters, so as scarcely to be distinguished from 

 specimens naturally curved. Let the access of oxygen 

 he denied, that the iron may not be oxydated, let 

 sufficient pressure be applied to prevent the disen- 

 gagement of the gaseous matters which sometimes 

 inflate the stone, and it is probable that no difference 

 would be found between the natural and artificial 

 specimens. Thus then we have a practical proof that 

 fire is adequate to the production of flexibility in rocks, 

 and are supplied with two distinct agents capable of 

 answering the desired conditions. 



It is next necessary to inquire what facts can be 

 produced to prove that the strata, the flexibility of 

 which has thus been shown to exist, or to have exis- 

 ted, have been bent by force. 



It was shown that where quartz rock and argilla- 

 ceous schist alternated, the former was broken at the 

 points where the latter was only bent. The fracture 

 here proves the application of force, of that power 

 which bent the flexible stratum. In innumerable 

 eases, the same strata, flexible enough to yield in a 

 limited degree, but rigid beyond a certain point, have 

 submitted to the moderate curvature, but have bro- 

 ken where they could bend no longer. Facts like 

 these can leave no doubt respecting the exertion of a 

 force producing both these effects. 



