Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/42

 rock of Jura; yet there are evident marks of stratification, which in many places are sufficiently regular and extensive to justify the belief that it has once possessed a greater degree of regularity and extent, which have been disturbed by subsequent changes. The predominant colour is a bluish or greenish grey, and its most general aspect that of a compact splintery quartz, often obscurely granular, and every where traversed by veins of ordinary white quartz. At Kyleaken it has a brown colour and a flat appearance, but becomes white and harsh on exposure to the weather, in consequence of the decomposition of the felspar which it contains. The great thickness of the mass here, compared with the thinness of the similar rock at Loch Eishort, is no proof of non-identity, since in so many other cases we find strata differing, in perhaps as great a degree, in thickness where we have the most satisfactory evidence of their continuity. I have not observed this rock in any other part of Sky, and it will presently appear that it could not be expected any where but beneath the sandstone near Loch Scavig. I shall not be surprised if it exists at the southern side of Soa under the sandstone beds, since that is its place, but this part of that island was unfortunately the only one which I could not reach. That it is a bed of great extent in this country, although so little visible, is confirmed by its being found in Rum, and in the same position, as I have ascertained.

The rock next in order to this is the red sandstone, and the connection between the two is equally distinct at Loch Eishort, where they are found following each other in a regular order and in intimate contact, there being indeed a gradual passage from the blue quartz rock into the red sandstone by a series of intermediate changes both in point of hardness and colour. The same transition will be found near Kyleaken on the eastern side, although I cannot