﻿I860.] 



NICOL N.W. HIGHLANDS. 



101 



granite, but I could find no place where it is seen to dip below the 

 gneiss. Even in the deep ravines of the Alt-na-CaiUich, close to the 

 line of junction, where the eastern gneiss is exposed for a thickness 

 of some hundred feet, I could discover no limestone below it. This 

 is the more remarkable as, from the enormous protrusion of igneous 

 rocks on the west, some such anomalous features might have been 

 expected to occur*. 



Elphin and Craig-a-Chnockan. — Having now noticed all the sec- 

 tions adduced in proof of the eastern gneiss overlying the limestone 

 and quartzite, I shall pass more rapidly over some others in the 

 southward extension of the line of fracture, though not less in- 

 teresting and instructive. To the south of Loch Borrolan and the 

 Strath Oykill road the country is flat and obscured by moss and drift, 

 but the limestone and quartzite appear to be thrown west to the east 

 end of Loch TJrigill. The whole eastern anticlinal of Ben More and 

 Brebag has in this region been swept away, and the line of junction 

 is in the continuation of the synclinal passing through the Gillaroo 

 Loch. So extensive has been the denudation of the overlying quartz- 

 ite and limestone that the gneiss is almost continuous from west to 

 east. True granitic gneiss with syenite -veins is seen very distinctly 

 at the east end of the Camaloch, whilst, according to Mr. Cunning- 

 ham, gneiss also extends from the upper part of Loch Urigill into 

 the Cromalt Hills. 



Bound Elphin the limestone is very well seen, resting, as usual, 

 on the fucoid-beds and quartzite (dip 12°-15°, to E. or E. 10° S.). 

 These beds are very fully exposed for some miles, and their relation 

 to the eastern gneiss clearly shown in the precipitous cliff of Craig- 

 a-Chnockan, below which the Ullapool road passes. The section 



Fig. 10. — Section on the Ullapool Road, near Elphin. 



d. Limestone. c". Fucoid-beds. cK Quartzite. b. Red sandstone. 

 a. Gneiss. • x. Granitic vein. 



fig. 10 shows the structure of this place. In the west, Coulmore 

 consists of the Bed Sandstone. The valley below is quartzite, ex- 

 tending up to the cliff of Craig-a-Chnockan. In the line of section it 

 dips 12°-15°, to E. 40° S., and is covered by the limestone. Further 

 east the limestone rises up and thins out, and the quartzite comes 



* The section fig. 5 (p. 223 in Quart. Journ. Geol. Soc. vol. xvi.), though said 

 to occur to the east of Alt-Ellag (where I am not aware that any quartzite or 

 limestone is to be found), probably refers to this locality ; but I could observe 

 no place where the beds rest connectedly on each other as there represented. 

 Even m it, however, the sequence is broken by " hornstone-porphyry ;" and the 

 "gneissose limestone" is perhaps also an intrusive rock. The absence, too, of 

 the fucoid-beds and limestone idHheir normal form is opposed to any regular 

 upward succession in that section. 



