Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/50

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Dr. Berger on the Isle of Man.

Dauby-point, and in the intervening space between Peel-town and Kirk-michael.

Cronk-dhoo is the highest place where I have observed the grey-wacke. The shade indeed that seems to discriminate it from the clay-slate is so delicate, that were I to speak decidedly it would be rather unphilosophical. It has a grey colour inclining to a greenish hue, the joints ferruginous; it possesses a silky lustre which it seems to derive from talc intimately blended or interwoven with the basis itself, but there are besides a good many small specks of mica.

At Banks-how the grey-wacke has a much more decided character. It is rather thick slaty and of a granular texture, traversed by veins of white quartz standing out in relief. The basis has a greenish tinge approaching to grey, contains no spangles of mica and comes near to quartz sandstone. When disintegrated it forms but a meagre soil, fit for little else than oats.

Large tabular masses distinguish the grey-wacke of Clay-head. The fracture in the small is granular-scaly, the colour greenish grey, passing to ferruginous on the natural joints, it does not fuse unless where there are spangles of mica.

Near Laxey there is a grey-wacke-slate used as flags for flooring houses, it is scarcely fusible but for the mica there is in it, thin coatings of an ash-grey colour over-run the surface.

The following beds of grey-wacke-slate, alternating with each other, appear on the south quay of Douglass.

First variety. Texture earthy, of a dirty grey colour, contains spangles of mica, fuses into a whitish enamel.

Second variety. Striated, of an hard and dry aspect, infusible, or merely glazed from the mica that enters sparingly into its composition. The colour varies from greyish to olive-grey.