IN GLEN TILT. 307 



the rocks, which the violence of the stream has exposed 

 in many parts of the channel. The substances of which they 

 consisted, to a point rather more than a mile and a quarter be- 

 low Forest Lodge, and marked by the letter A in the map * 

 (Plate XXL), and the plan of the river (Plate XVI.), were, as 

 far as we observed them, gneiss, mica-slate, and granular lime- 

 stone. 



7. On the west side of the valley, between Gilbert's Bridge 

 and the opening of Glen Merk, a great quantity of fragments, 

 brought down by torrents from the steep bank of the moun- 

 tain, consisted chiefly of mica-slate ; though there were among 

 them a few small ones of sienite. Mica-slate may, therefore, 

 be inferred to be the prevailing rock on this side, and some 

 strata of it, near the brow of the declivity, were distinguishable 

 in the bed of a torrent, even from a distance. Strata of mica- 

 slate occur also at the falls of the Alerk, near its junction with 

 the Tilt. Farther up, on the same side of the valley, where 

 the road crosses the Criny, that stream flows over some beds of 

 granular quartz. 



8. On the eastern side of the valley, we often found granular 

 limestone near the road, between Gilbert's Bridge, and ano- 

 ther about two miles farther up, called Gow's Bridge ; and a 

 quarter of a mile beyond this, limestone is visible from a dis- 

 tance, in a scar on the same side, and th^ee or four hundred 

 feet above the bed of the river. 



9. Through all this part of the Glen, the stretch and dip of 

 the strata are tolerably uniform. In four observations f made 

 between a point a little below Gilbert's Bridge, and Gow's 



Bridge, 



* The outline of the map is copied from Stobie's Map of Perthshire. An at- 

 tempt has been made to give a better representation of the mountains near Glen 

 Tilt ; some names have been added, and others have been differently spelt, with. 

 a view of conveying the Gaelic pronunciation more distinctly, 



f An observation at the falls of the Merk is included. 



