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PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



[Feb. 6, 



of the River Garry, both above and below Dalnacardoch. Above the 

 inn, the quartz-rock, in well-bedded fissile flagstones, dips to the S.E. 

 at an average angle of 30° to 35°. Several small dykes of felspar- 

 porphyry, running along the strike of the beds, occur about three- 

 quarters of a mile to the north-west of Dalnacardoch. The south- 

 easterly dip continues for three miles up the Garry, though towards 

 the end of that distance it becomes subject to undulations, showing 

 that the strata are on the eve of turning over in an opposite direc- 

 tion. This reversed or N.~W. dip is well seen in the channel of a 

 torrent on the right-hand side of the glen, about three miles north 

 of Dalnacardoch. There, grey flaggy quartz-rock dips N. 42° "W. 

 at about 30°. The stream has brought down an immense quantity 

 of shingle from the hillsides, chiefly of grey quartz-rock, with not a 

 few fragments of reddish felspar-porphyry. Above this, the bottom 

 of the valley is drifty and alluvial; but the colour and form of 

 the bounding mountains left us in no doubt that the same quartzose 

 series extends northward beyond the Pass of Drummuchter. 



The descent of the Garry from Dalnacardoch exhibits a clear 

 ascending section of quartzose flagstones, occasionally schistose and 

 micaceous. The dip is as nearly as may be S.E., and the angle 

 ranges from 25° to 60° or 70°. Even allowing for some reduplica- 

 tions, the thickness of this series must be very great. Here and 

 there, as at 5|, 4|, and 4^ miles respectively from Blair, dykes and 

 masses of felspar-porphyry occur, with a general strike from N. by E. 

 to S. by W. Two miles and a half from Blair the series is terminated 

 by the superposition of a very thick limestone series. 



Blair- Atholl and Glen Tilt. — In following out the curvatures and 

 breaks of the rock-masses and their reappearances in a regular se- 

 quence as we proceeded from the north-west to the south-east, it was 

 evident, from proofs of superposition only, that when we came to the 

 south-western flank of the Grampians we had once more reached the 

 upper crystalline series. On a former occasion a similar ascending 

 succession to the younger stratified crystalline schists, whether mi- 

 caceous, quartzose, or chloritic, with bands of gneissic character and 

 argillaceous slates, had been traced from the heart of Ross and Inver- 

 ness to the northern, eastern, and south-eastern flanks of the Gram- 

 pians, as seen in the counties of Moray, Banff, Aberdeen, Kincardine, 

 and Forfar*. To the last of these tracts we shall presently advert. 



In examining the south-western flanks of the Grampian chain 

 near Blair- Atholl, it was indeed quite manifest, judging even from 

 the flaggy and schistose characters of the rocks, that we were already 

 among strata superior at all events to the lower quartz-rock and 

 limestones of the north-west. Glossy shillat with micaceous schists, 

 resting upon granular quartz-rocks and limestones, and even alter- 

 nating with them, presented to the eye a mineral development un- 

 known in the lower members of the altered Silurian rocks of the 

 North-west, and wholly unlike anything in the Cambrian rocks and 

 fundamental gneiss of the outer Hebrides and the west coast of 

 Sutherland. 



* Quart. Journ. Geol. Soc. vol. xv. p. 389 et seq., and vol. xvi. p. 237, &c. 



