Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/275

 the larger masses of granite with the same ease as when they traverse the schist: in others, however, they appear both to originate and end in the limestone, and present rather the aspect of detached lumps and irregular processes than of veins. So confused is this interference, that a fragment of granite is often found entangled in the limestone, and a lump of the latter will sometimes be found intruding into the former. The minuter veins of granite are generally if not always connected with the larger pieces, and they intersect and reticulated the whole limestone as they do the schist, diminishing at length to the thickness of a leaf of paper or a thread. But there is a still more remarkable arrangement of the limestone and granite. Parallel to the limestone bed or beds, and following every flexure and contortion which it undergoes with the most perfect regularity, are to be seen narrow lines rising above the general surface, and accompanying the course of the bed through its whole extent. On examining them they are found to consist of a harder substance which has resisted the action of the water, while the softer and intermediate parts, being of limestone, have been dissolved and washed away. The fracture of the rock shows that these are the edges of laminæ formed of a reddish siliceous substance precisely similar to that which constitutes the reticulations, and which from the contrast of its colour to that of the blue limestone with which it alternates, is always easily distinguished.

Having blown up a considerable portion of this rock, I am enabled to say that it is of a laminated texture throughout, being a bed of which the alternate layers are limestone and that siliceous red rock which I consider as a modification of granite. A perfect notion of such a limestone may be formed by recollecting the appearances