the depth of some hundreds of yards ; 

 but in all these, a very few only excepted, 

 the whole of each is not one continued 

 mass, but is again subdivided into a great 

 number of thin laminae, that seldom are 

 more than one, two or three feet thick, 

 and frequently not so much " (Art. 38). 

 This careful observer next describes 

 with minute precision the system of per- 

 pendicular fissures (or what are known as 

 joints) by which the stratified rocks are 

 so abundantly traversed. He notices the 

 frequent bent position of the strata, and 

 shows that their inclination increases as 

 they are traced towards the mountains, 

 which are generally, if not always, formed 

 out of the lower, and therefore older rocks. 

 He illustrates the subject by the follow- 

 ing experiment. "Let a number of 

 leaves of paper, of several different sorts 

 or colours, be pasted upon one another : 

 then bending them up together into a 

 ridge in the middle, conceive them to be 

 reduced again to a level surface by a plane 

 42 



