Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/89

 durable and compact basalt. I have given a sketch of it. (Pl. 2. fig. 3.) I may finish the description by saying that the continuations of these veins are to be seen between Swenish and Kilbride, at least, veins similar in appearance and equally numerous, but that there is no trace of them on the opposite shore of Sleat in the places which their prolongations would cut: they are not therefore extensive in their courses.



It has been so general an observation that the courses of trap veins are attended with disturbances of the accompanying strata, that it seems almost to have passed into a rule among geologists. The present instance is a most remarkable one to the contrary. Although they are here so numerous, not the slightest disturbance takes place in the evenness and the horizontality of the strata of sandstone which they intersect. There is neither contortion, bending, fracture, or displacement, nor do they appear to have affected the texture of the rock, since it is the same both at the place of contact and at a distance from it. Of exceptions to general rules it is rare to meet with any so pointed and so strong; and though there is no room for any long commentary on it, I cannot entirely quit this very remarkable place without pointing out one extraordinary effect which must have resulted from the intrusion of these veins. If the lateral dimension of the collective veins is assumed at one tenth of that of the stratified rock, (and I have reason to think this estimate not excessive) it is plain that the stratified rock of Strathaird must have undergone a lateral extension equal to that quantity; a motion so great that it is extremely difficult to reconcile it with the present apparent repose and regularity of the whole.