﻿I860.] 



NICOL N.W. HIGHLANDS. 



93 



miles to the east of the sections just described. On the east side 

 of the Kyle of Tongue several remarkable masses of red conglo- 

 merate rest on the gneiss. These have hitherto been allowed to 

 remain in the Old Red or Devonian formation, though separated 

 from the nearest undoubted Old Red strata, on the east of Strathie, 

 by an interval of eighteen miles. This summer (1860) I examined 

 these conglomerates, in the expectation that they might throw some 

 light on the history of this western region. They consist of rounded 

 or angular fragments of coarse- or fine-grained gneiss, mica-slate, 

 granite, felspar-porphyry, and vein-quartz ; but I could find no trace 

 of the red sandstone, quartzite, or limestone, which now form the 

 great ranges of mountains in the west. This entire absence of any 

 fragments of these rocks, which have formerly covered to the depth 

 of some thousand feet a tract of country forty or fifty miles wide 

 and more than a hundred miles long, and not ten miles distant, 

 seems 1 altogether inexplicable on the supposition that the two 

 deposits are of widely different age — the one Cambrian and Lower 

 Silurian, the other Old Red or Devonian. The conclusion seems 

 therefore irresistible that these Tongue conglomerates are identical 

 in age, as they are in mineral character and composition, with the 

 red conglomerates and sandstones of the west coast. This identity 

 is confirmed by the occurrence of the overlying quartzite on Cnoc 

 Craggie, near Loch Laoghal. The greater part of the hill consists 

 of the conglomerate overlain on the south side by the quartzite in 

 thick irregular beds. The preservation of these interesting frag- 

 ments seems due to the great syenite-eruption of Ben Laoghal, 

 which has at once hardened the beds and preserved them from 

 removal by denudation. In this place, therefore, there is clear evi- 

 dence that so far from underlying all the gneiss of central Suther- 

 land, the red sandstone and quartzite of the west are again found 

 resting upon it ten miles to the east of the supposed overlap. 



Loch More Section. — The next point to the south where the quartz- 

 ite is said to be overlain conformably by gneiss is near the north-west 

 end of Loch More. In Mr. Cunningham's section this relation of the 

 rocks is very distinct ; but on the ground the phenomena are quite 

 opposed to this view, as shown by the section fig. 6, the result of a 



Fig. 6. — Section on the South Side of Loch More. 



^' Ben Stack. Craig Dhu. Ben Leick. 



c 1 . Quartzite. aa. Gneiss with granite veins. a. Gneiss. 



x. Granulite (termed " gneiss " by Mr. Cunningham). 



careful examination of the locality in two separate seasons. At the 

 western extremity of Loch More, the quartzite (c 1 ) rests in a long 



