Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/239

 calcareous spar, and exactly resemble those which occur in the trap rocks themselves.



I remarked above, that the schist is often much contorted and mixed with the trap. This mixture affords a great variety of appearances, a variety so great that no limited series of specimens, nor any drawing less than that of the whole face of the hill itself, could give an adequate idea of them. The accompanying sketch exhibits one of the most general. In many parts innumerable detached fragments may be seen imbedded in the trap, the whole of the schist displaying a greater disorder and confusion than the sandstone does in any of the instances hitherto described. In a few places another singularity may be remarked. Veins of different dimensions, and ramifying in different directions, are to be found traversing considerable portions of the rock, and in some instances terminating in the schist, with which they are continuous. As the schist graduates into the vein, its laminated texture disappears, but in other respects there is an identity of composition between the vein and the laminated schist, at least for a considerable space. The same loss of the laminated texture of the schist takes place wherever, from its proximity and intermixture with the trap, it is materially perverted from its original even direction. In other respects the identity of substance is here, as in the other case, preserved, nor is any decided line drawn to determine the discontinuation of the laminated structure, either in the progress to contortion or ramification. However contradictory it may appear at first sight, that the same substance should exhibit both the character of a laminated and bedded rock and that of a vein, the state of the incurvated and contorted masses may perhaps by analogy assist in solving the difficulty. It is not an unreasonable supposition, that