﻿1861.] 



S1UECHIS0K AKD GEIKIE— HIGHLAKES. 



217 



the strata are highly argillaceous as well as micaceous, dipping S. 50° 

 W. at 42°. At the manse a seam of limestone Avas formerly quarried. 

 "Where the road crosses the Orchy, sandy micaceous schist dips S. 60° 

 "W. at 45° to 55°. The same south-westerly inclination continues 

 towards the head of Loch Awe. Beyond Stronmelch, the greenstone 

 dyke already described descends from the hillside and plunges below 

 a drift-covered peaty plain. The strata at the head of Loch Awe 

 seem to be greatly contorted, having in places even a north-westerly 

 dip. Another dyke of greenstone, possibly a prolongation of the second 

 ridge at the foot of Glen Orchy, which we conjectured to consist of 

 greenstone, crosses the road on the west side of the Loch Awe valley 

 a short way south of the point where the road crosses the Main 

 "Water. Quarter of a mile from the bridge a streamlet has laid open 

 a good section of some quartzose flagstones, micaceous and chloritic, 

 dipping S. 52° "W. at 35° to 40°. 



We made copious notes of the section along the western shore of 

 Loch Awe to the outlet of the river, but we need only cite here one 

 or two of the more important facts. The dip, sometimes reversed 

 and frequently varying, maintains on the whole a south-westerly 

 direction, and the strata become very schistose as we ascend in the 

 series. Mica, chlorite, and talc are the distinguishing minerals. 

 About seven miles from Dalmally a bed of hard siliceous limestone 

 occurs, with occasionally a green serpentine colour, and many thin 

 talcose seams. It also contains lenticular masses of white quartz, 

 and dips S. 54° "W. at 48°. Above this limestone come several 

 other bands of a similar rock, forming as a whole a thick limestone 

 series. Serpentine abounds, giving the beds a green colour. Felspar- 

 porphyry is also abundant, both in the form of beds parallel to the 

 planes of stratification, and also as veins cutting through the strata 

 irregularly. This porphyry deserves remark. "Where disposed in a 

 bedded form, it is traversed by lines of quartz corresponding exactly 

 to the lines of bedding of the adjacent limestones and schists. It 

 contains much talc, which, however, is invisible in the cross fracture, 

 but shows a silvery surface along lines parallel to the bedding-planes. 

 Otherwise the rock appears to consist mainly of pink felspar. The 

 aspect of these porphyries more than once suggested the idea that they 

 were only more highly mineralized portions of the stratified series 

 that had been metamorphosed in situ. 



The schists with innumerable dykes and veins continue down the 

 Pass of Loch Awe. They appear eventually to be reversed to S.E», 

 showing thus the commencement of the other side of the trough 

 which begins with the south-westerly dip of the strata in Glen 

 Orchy. The granitic region of Cruachan Ben intervenes between 

 the Awe and Loch Leven, rendering a careful examination necessary 

 before the geological lines at these places can be safely joined. In 

 the meantime, however, we regard the sj'nclinal trough of Balla- 

 hulish as a continuation of that of the Awe— an inference which 

 the general strike of the strata at both localities and over part of 

 the intermediate ground seems to render probable. 



Dalmally to Tyndrum. — The section up the glen from Dalmally 



