104 PEOF. T. G. bonnet's PETEOLOGICAL NOTES ON THE 



kind of gneiss, with a structure generally resembling the quartz- 

 schists described below, but containing a little more felspar (decom- 

 posed). The difference, however, is simply varietal. 



Fig. 6. — Mica-scTiist from the wpper part of Glen Doeherty 



{Newer Series of Author), 



It is quite true that the mica-schists in the road dip (at about 30°) 

 a little W, by S., and that in the ravine about to S.W. The dip of 

 the gneissic rock a little above is nearer to the former ; but on the 

 opposite side of the glen the rocks appear to preserve the usual south- 

 easterly dip ; and these quartzose beds have a very shattered aspect ; 

 so that I have not the slightest doubt the change of strike is merely 

 local, and due to the neighbouring fault, as in the case already 

 described. 



Between this point and Auchnasheen little rock is exposed near the 

 road, but nothing in the terrain suggests the introduction of any 

 group other than that from which Glen Docherty is excavated. From 

 Auchnasheen I ascended Ben Fyn, mounting by the right hand one of 

 two streams visible from the inn, and returning (in part) by the 

 other. A small quarry, about 200 ft. above the inn, gives a good sec- 

 tion of a gneiss with red garnets. The rock is flaggy in structure, 

 well foliated parallel to its bedding, dipping towards the E. at about 

 30° (rather rolled), having a general resemblance to the newer series 

 to the north-west, but more highly altered. Under the microscope the 

 rock is seen to consist of quartz, clear (with exception of some small 

 microliths and very minute cavities), orthoclase felspar, with some 

 plagioclase in good preservation (long colourless belonites are present 

 in some of the crystals), biotite and a little of the white mica already 

 described, and opacite, with two or three garnets. The rock is more 

 highly altered than the rocks already described, but stiU presents 

 some structural resemblance to them*. Above this for some 1200 ft. 

 the rocks continue to be flaggy, occasionally most conspicuously, but 



* Some of the grains show a minute " graphic " or, rather, vermicular structure. 

 Cf. ' Nature,' xiv. pp. 8, 68. 



