quartz rock, and we have also seen that the calcareous beds themselves alternate with beds equally continuous of quartz rock and of schist. We have seen that the great mass of quartz rock is followed by a small bed of limestone, and that this again is succeeded by micaceous and clay slate, terminating the series of the bedded rocks in this direction. Here then is an order of rocks different from that which we are taught to believe universal, since the micaceous schist is far removed from the granite, and only follows a succession of limestone and quartz rock. It is the limestone which immediately follows the granite, and that granite is probably a portion of the great mass which forms the central granite of Scotland.
This contact of the limestone and granite is too well marked to admit of dispute, however, like many of the other remarkable circumstances attending on Glen Tilt it has been overlooked.
But there are other important phenomena which accompany the junction of the limestone with the granite. Recurring to the alternations between the limestone and the beds of schist and quartz rock with which it is continuous, we find that these alternations are regular, even, and defined. But if we now trace downwards to the granite, we do not find any one of these beds continuously in contact with the granite; on the contrary it is sometimes the schist, sometimes the quartz rock, sometimes the limestone, or there is a want of conformity between the granite and the rocks which lie above it. This is not the appearance which we ought to expect had the superincumbent strata been deposited on the previous basis of granite. If the granite had been the lowest of a series of deposited rocks and the basis on which the incumbent ones were precipitated or crystallized, all the strata which lie on it should have followed upwards from it in a regular order of succession. That rock which was contiguous to the granite in one place
