Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/321

 should have been contiguous to it every where, since this law is invariably found to hold good among rocks of which the stratification is demonstrated. This observation is of importance, and I have illustrated it by two sections, the one showing the fact as it actually exists, and the other the order which should take place had the strata been regularly deposited on the granite. In addition to the irregularity of this line of contact, symptoms of confusion and disturbance are apparent, in every instance where the granite is actually visible in contact with the neighbouring rocks. These consist in a general mixture of all the stratified rocks with the granite, and a total discomposure of their regularity, being at the same time accompanied by the passage of minute veins from the mass of granite into the stratified rocks. Where on the contrary the beds lie out of the immediate vicinity of the granite, they retain their parallelism and regularity, its influence appearing to extend to a very short distance beyond the point of actual contact.

The real structure of Glen Tilt, and the true cause of the appearances which have excited so much notice, must now be seen so clearly to follow from the history of the rocks which bound it, that it is almost superfluous to give a summary view of the whole. I will however conclude this account with such a sketch, illustrating it by a map and such sections as may render the whole more obvious to those who may be inclined to follow me over the same tract. The map does not pretend to minute accuracy with respect to every rock over this large space. It would have been in fact impossible to have laid down such details on a survey of this mature, the only one which has yet been executed of this district.