Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/407

 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 containing 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 subsidence may be easily estimated.