Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/284

 unintelligible. I may only say that schist, granite, and quartz rock of different aspects, with occasional masses of porphyry, succeed each other so frequently that the whole might be considered by those who are prepossessed respecting systems of alternation, as a demonstrable instance of this disposition. I hope to give a more correct view of their connections hereafter. On the left bank I may also generally remark that a succession of dark blue limestone, rarely interrupted by schist, quartz rock, and granite, is seen on the left bank from Poll Tarff down to this place, and even beyond it as far as Gow's bridge.

An alluvial blank of about 800 yards follows this marble rock, which is succeeded by 100 yards or thereabouts of granite; and after 150 yards more of an alluvial space, a large mass of rock for the space of 200 yards and upwards is found traversing and obstructing the stream, so as to form a cascade. This very irregular mass of rock consists of granite and quartz rock united. The quartz rock is of a peculiar aspect, being of a bluish colour, very uniform and compact and approaching near to common quartz in character, but still shewing evident marks of foliation. It is disturbed and intersected by the granite in a way which I need, not now repeat. A thin stripe of limestone and schist may also be seen interwoven in the granite. Below the cascade there is once more a blank alluvial space of 100 yards, which is succeeded by quartz rock for about the same space; immediately after which occur about fifteen yards of a yellowish and greyish limestone or marble, very hard, and disturbed and traversed by granite in the way already described. This is followed by a series of limestone beds for about 200 yards, the first of which is blue and the last five or six of a yellowish aspect: these are almost the first limestone beds observed in descending the river which have the same general dip and position with the beds of the mountain on the