Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/272



It is not far below this place, but at a distance which I have neglected to note, that a great portion of a limestone bed will be found crossing the river. It is much contorted, and is also reticulated with a few granite veins. Here the alternation of the limestone with the quartz rock is also visible, and they cross the river together. The limestone is in this place uncommonly hard, and in its composition very siliceous. Its external aspect where it is worn by the action of the water, is not much unlike that of a granite or porphyry, and it has in fact been sometimes mistaken for one or other of these rocks. Continuing to descend nothing remarkable occurs till we arrive within about two miles of Forest lodge, where a rock like those last mentioned, traverses the bed of the river. This rock consists of a great mass of red granite so mixed with quartz rock and hornblende schist, that neither pen nor pencil can describe their confusion. Limestone may be observed both at its upper and lower edge, and this is traversed and reticulated by small granite veins. The whole mass occupies a space of about 150 yards. It is proper to remark here, that the blanks which occur in this account of the bed of the river are such as in general arise from its course being over a bed of alluvial matter which covers and conceals the fundamental rock, while in other cases they arise from those portions of the natural bed which are visible being trivial or unimportant, or from the state of the water which prevented its bottom from being seen.

The next, and of all perhaps the most remarkable rock to be observed in the course of the Tilt, occurs at a bridge a short distance above Forest lodge. A large mass of red granite is first seen occupying the bed of the river for a considerable space both above and below that bridge. Associated with this mass of granite are various rocks, so disposed and intermingled that neither description, nor drawing,