Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/287

 granite, is that of one solitary and small vein, of a grey colour, which intersects the schist immediately above the bridge; the disturbance however produced by it is trifling. Another disturbance, although small in extent, is very remarkable, though not unique, since I have found a similar occurrence in Iona. Below the bridge on the left bank a bed of white marble is seen surmounted by a bed of hornblende schist. This is followed by a second bed of the marble about two feet in thickness, of which the greater part is suddenly cut off at right angles to the bed by a second mass of hornblende schist, while the lower part continues in the same direction, but bent, and of the breadth of only two or three inches. The lower part of the mass of hornblende schist, which thus intersects the marble, is also protracted in a thin plane continuous with the thin part of the marble and lying above it, while the upper side of the same becomes continuous with a regular and thick bed of the schist. Between these two portions of the schist there is interposed a thick bed of the marble, which is therefore included on three sides within the hornblende schist, its outer extremity being cut through at right angles by the schist. As the beds dip into the hill, the further progress of this extraordinary arrangement cannot be traced. A drawing accompanies this description, which words can scarcely render intelligible. The appearance now described is interesting, since it is connected with phenomena of no very uncommon occurrence, which have given rise to much controversy. It is evident that both the prolongation of the limestone and that of the schist bear a great resemblance to the veins, which, in the case of granite, may be traced from a mass of that substance into the neighbouring rocks: yet there is no doubt that both the limestone