Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/57

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47
Dr. Berger on the Isle of Man

On the slope both of South Bor-roilva and Cronk-ne-liry-Lhaa, in the southern part of the group of mountains, occur abundant blocks of rather decayed granite, composed of yellowish and white felspar turning to a state of earth, and disseminated plates of white mica. The texture is loosened to such a degree that large fragments often yield under the pressure of the hand.

I traced blocks of the same granite in Glen-Moy, though the bed of the stream is hollowed out in the grey-wacke formation.

The central stone of a Druidical barrow[1] in Kirk Ballaugh, is a small grained granite of white felspar, quartz, mica, and a great deal of hornblende.

†† Mica-slate.

A vast number of blocks of mica-slate exist on the slope of Slieau-y-Carnane, another hill in the southern district of the group. The quartz is finely granular, and has a silky lustre, which it probably derives from a superficial covering of talc. The plates of mica are white and sparingly dispersed, sometimes crystallized.

I met at the village of Craig-neash with a large settled block of mica-slate. The quartz is of a dirty-grey colour. The plates of mica very few and falling into decay.

††† Porphyry.

Very numerous blocks of this rock occur on the beach at Aire-point. The basis is compact felspar of a flesh-red colour, turning

  1. All the Runic or Danish monuments so frequent in the Isle of Man, are (as far as my observation has gone) of greywacke, without one single exception. The inscriptions they bear are said to be written in the old Norwegian language: they are placed on the edges of the stones, whereas the carvings are on their flat surfaces. The latter appeared to me to bear some resemblance to the form of a snake.