Dr. Mac Culloch on a Vein in Limestone. 397 



clay acquires on drying, and where the calcareous earth, resident 

 in the mass itself, or in the surrounding beds, has been gradually 

 brought into solution by water, and deposited wherever it could 

 find a cavity in which to crystallize. 



In the diagrams Nos. 3 & 4,* I have supposed a section of the 

 rock containing the vein, for the purpose of exhibiting the number 

 and extent of the slides which must have occurred to produce its 

 present position. Where similar appearances are observed on a 

 large scale, it will be apparent how much the form of the contain- 

 ing rock must change to admit of the motion of the included vein, 

 and how the subsidence of a mountain must have followed the 

 sliding of a large vein ; from which slide also the quantity of sub- 

 sidence may be easily estimated. 



* PI. 26. 



Vol. iv. 3 e 



