SKY. GEOLOGY. RED SANDSTONE. SOI 



schists and other substances share largely with it in the 

 tract to be described, but the adoption of either of these 

 would have been still more objectionable. 



It was already shown that the boundary of the gneiss 

 at Loch Oransa is definite, and from this point it will 

 be most convenient to commence the present examination. 

 But. it is impossible even thus- to pursue this investigation 

 in the usual regular order from the lowest to the highest 

 of the entire series, even if the lowest could actually be 

 ascertained throughout the whole line. The causes of this 

 will be found to consist in the varying composition of 

 the beds, taken longitudinally, or according to their direc- 

 tion. Hence it happens, that although certain portions 

 are regularly prolonged in the rectilinear direction, they 

 will be found to present different substances throughout 

 their course, just as they do when examined transversely, 

 or according to the order of their succession. It will 

 therefore be necessary to select certain portions of the 

 whole in a transverse order ; noting the chief differences 

 that occur, and connecting them as much as possible by 

 those features which are common to all, namely, their dips, 

 bearings, and connexions with the rocks above and below. 



With trifling exceptions, which will be noticed in their 

 proper places, the bearing of the whole series corresponds 

 to that of the gneiss, and is therefore north-easterly. But 

 the dip is so various and uncertain that the record of 

 the particulars must be referred to the details of parts, 

 since it is in different places both easterly and westerly 

 under various angles; while the strata often assume the 

 vertical position also. As the most systematic regularity 

 of the gneiss is found near Loch Oransa, so the position 

 of the red sandstone is there also most uniform. 



The gneiss at this place is of a decided character, and 

 is followed towards the north-west by a few thin beds 

 of micaceous schist ; unless the presence of occasional 

 grains of felspar only distinguishable by the lens, should 

 induce mineralogists to consider this rock as a variety 



