Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/175

 usual place in the one case as the graywacké is in the other. But the island of Sky is very often unsystematical: that which follows perhaps still more so than that which has preceded.

In attempting to trace the red sandstone below, or rather beyond the white quartz rock, it is not found to terminate on the north-western shore of Sleat, at the place where, according to the line of direction prolonged from Isle Oransa, it should end. Instead of that, the alternations of sandstone and schist continue. Gradually however they increase in frequency, and becoming at length undulated and contorted, they cannot at a distance be distinguished from gneiss in their general aspect and disposition. In examining the substances, the first alteration perceived is the gradual induration of the sandstone, which becomes first a compact quartz containing grains of red felspar. At length the felspar acquires a laminar tendency, the schist still remaining unchanged, the rock thus becoming an irregular gneiss (if it may be so called) consisting of laminæ of quartz, felspar and graywacké schist. Approaching the point of Sleat the schist gradually becomes green and glossy, thus passing into chlorite slate, and here we arrive by an insensible gradation to the variety of gneiss which I formerly described as found there. In thus pursuing the red sandstone on the western side of Sleat, the reason appears why I could not when speaking of that rock, define the boundary of the gneiss on this side of the island, and I need now scarcely repeat, that any attempt to examine rocks so constituted, in the interior country, would leave nothing but doubt and uncertainty; for which reason I have limited the description to the sea coast, where every foot of the rock through all its transitions admits of free examination.

I have no commentary to offer on these facts, which seem calculated, if not to excite disbelief, at least to set our present systems