SKY. GEOLOGY. RED SANDSTONE. 315 



the same rock is only ascertained by its position and 

 mineral structure. In position it corresponds to the 

 strata of Sleat, having a north-easterly direction and 

 a western dip ; while, its composition resembles the 

 uppermost of these, consisting of red sandstone alter- 

 nating with the blueish rock and with graywacke schist. 

 The overlying position of the superincumbent trap is 

 distinctly visible, as well as its contact with the strata ; 

 which are also traversed by numerous veins of the 

 same substance, that do not however materially affect 

 their regularity. Gravelly and conglomerate beds occur 

 in this portion, and, like the former, it sometimes puts 

 on the schistose structure. As, from its disjointed state, 

 it presents, like that of Sligachan, no connexions that 

 admit of tracing its relation to the great mass of sand- 

 stone or to the other regular rocks, I shall defer the 

 consideration of this subject till a future time, when the 

 examination of some of the isles adjacent to Sky will 

 assist in throwing light on its history. In the meantime 

 I may remark, that the position and western dip of both 

 these detached portions, that of Scavig and that of 

 Sligachan, give them the appearance of lying above the 

 limestone, as I already hinted at the beginning of this 

 article ; a position which I shall attempt hereafter to re- 

 concile with the ordinary arrangements in nature. 



I can not yet drop the subject of the red sandstone 

 without mentioning a circumstance which, although appa- 

 rently trivial on a first view, is not unimportant in esta- 

 blishing the connexion between Sky and the neighbouring 

 islands. 



On the shores of Fladda (the small island situated in 

 Loch Staffin) there are found numerous fragments of red 

 sandstone with a few of gneiss, both of them being 

 identical with the rocks of the opposite shores of Rasay 

 and Rona. It has already been seen that in the former 

 island the order of succession, from gneiss to red sandstone, 

 and afterwards to the strata that appear on the north-east 



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