186 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Beyond this point, near the foot of Loch Lubnaig, there is a great 

 mass of chloritic slate and greywacke, full of quartz-veins reticu- 

 lating in all directions, but with no determinable dip or direction. 

 It contains imbedded fragments of a more siliceous nature. The 

 coarse greywacke also is composed of fragments of quartz and felspar, 

 from one -tenth to one -fourth of an inch in diameter, in a basis of 

 grey chlorite or mica in fine scales. Even the coarser varieties have, 

 however, a distinctly foliated or schistose texture, unlike anything 

 I have seen in the South of Scotland. The grains of quartz and 

 felspar are flattened and drawn out in the direction of the foliation, 

 so that the rock presents, as it were, an incipient tendency to assume 

 the structure of regular gneiss*. As illustrating the metamorphic 

 origin of the crystalline strata, this rock is exceedingly interesting, 

 presenting, as it were, one of the intermediate steps in the process. 

 It is more crystalline than the greywackes of the south, less so than 

 the true gneiss of the north, and, though distinctly foliated, still 

 clearly fragmentary in origin. 



Beyond this point the strata become more regular, and less detail 

 is necessary. The first beds are greenish clay-slate, dipping about 

 40° or 45° to N. 42° W., and interlaminated with parallel veins or 

 layers of quartz with undulating surfaces, as if ripple-marked. 

 Further up Loch Lubnaig the dip rises to 75°, N. 37° W., in blue 

 talcose slates. Near Ardchullarie another vein of dark greenstone, 

 about 50 feet wide, runs nearly E. and W. by compass (E. 30° N.). 

 Soon after the true mica-slate appears, dipping at 73° to N. 15° W., 

 in thin undulating beds. It continues along the whole lake ; but 

 further up the strata become more contorted, and dip very irregu- 

 larly at lower angles. Though not quite conformable to the clay- 

 slate, the mica-slate clearly overlies that rock, seen further down the 

 loch. 



7. Leny Limestones. — On the hills to the east of the Pass of Leny, 

 limestone has been quarried for a long period. The excavations 

 follow the outcrop of the rock across the ridge of the hill, and in 

 some places are of considerable depth. In one part of the old quarry 

 there is the section represented in fig. 4. 



To the south are black shales (c), mixed with contorted beds and 

 masses of limestone. Above the shales is the limestone b, bine and 

 reticulated by veins of white calcspar, and now wrought out above. It 

 is covered by grey talcose beds (ajjand these by red shales (a 2 ) curved 

 and twisted. At x is a bed of red compact felspar-porphyry, with 

 grains of quartz and crystals of mica sparingly distributed through it. 

 The limestone is better seen in the quarry now being wrought, where 

 it is 15 feet thick, and divided into several thin, curved, and irre- 

 gular beds, dipping at 53° to N. 25° W. It rests on and is covered 

 by black shales, both dipping at 70° to N. 37° W., — thus, curiously 

 enough, both unconformable to the limestone between them. The 

 shales are covered by a red porphyry, identical with that in the 



* Professor Hitchcock, of Amherst College, has recently described a similar 

 appearance in America. See Silliman's Am. Journ. of Science, vol. xxxi. (1861) 

 p. 372, &c. 



