﻿1861.] 



MT7KCHIS0N AND GEIKIE— HIGnLANDS. 



177 



call special attention, not only to the N.W. strike of the beds of this 

 fundamental rock, as contrasted with the north-easterly strike of the 

 eastern rocks, but also to the marked distinctions in lithological com- 

 position between it and any of the overlying masses. 



The older gneiss which ranges along the north-eastern side of 

 Loch Maree, and rises in some places to several hundred feet above 

 the water, is unmistakeably the same hard, massive, and highly 

 crystalline rock as elsewhere in the outer Hebrides and the coast of 

 Sutherland. At several places it exhibits subordinate layers of fine 

 schistose limestone, which above the House of Letter-Ewe is encased 

 in dark-grey gneiss (fig. 1), occasionally schistose, with white quartz- 

 Fig. 1. — Section across Loch Maree at Letter- Ewe. 

 s.w. N.E. 



a 



a. Gneiss. a*. Schistose limestone. 



b. Cambrian sandstone and conglomerate. 



c. Quartz-rock. 



veins. This limestone, which has been quarried by the proprietor on 

 both sides of the torrent Fuolish, is for the most part a whitish or 

 cream-coloured, scaly, fracturing rock, and, though here and there 

 mixed with earthy greenish schist and gneiss, it is in parts a bril- 

 liant snow-white saccharoid marble. "Whether, therefore, we look 

 to its composition, or to that of the enveloping gneiss, this limestone 

 is as distinct as possible from the dull grey-and- white limestone, 

 which, subordinate to the quartz-rock and overlying series of strata, 

 has also a totally discordant direction. The one rock must therefore 

 have been formed long ages before the other. 



In the sequel we will endeavour to show, when explaining the 

 details of another section, that it is physically impossible that this 

 Laurentian gneiss of Loch Maree should, by any great upheaval, be 

 so placed as to lie conformably upon Lower Silurian limestone and 

 quartz-rock to the west of Krnloch Ewe. In the mean time we 

 would point to the geological map of Professor Nicol, to indicate a 

 serions erratum as to the direction of this limestone, which occurs in 

 the gneiss of Loch Maree. It is therein represented as directed from 

 N.E. to S.W., and therefore as passing across to the S.W. side of the 

 loch*. If this were correct, some persons, who have not visited the 



* Prof. Nicol has here, and in many other portions of his map, followed 

 Macculloch. 



