28 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 19, 



the gneiss, forming the rugged rounded hills between the Gairloch 

 and the lower half of Loch Maree. The gneiss is in general of a 

 light or dark grey colour, and finely granular ; but other varieties 

 are reddish, and more perfectly crystalline, or, again, contain distinct 

 granular concretions of quartz or small garnets. Interstratified with 

 it are beds of mica-slate, or fine-grained hornblende-slate. The strata 

 are often contorted ; but the general direction is nearly parallel to 

 Loch Maree, or about N.W. (from N. 40° W. to N. 60° W.), and 

 the dip almost vertical, or inclining to the south-west. The next 

 rock is the red sandstone ; the lower bed, where in contact with 

 the gneiss, as on the shore near Gairloch Kirk and on Loch Maree, 

 being a very remarkable breccia of quartz and gneiss in sharp angular 

 fragments, not at all rounded or worn. The quartz is white and 

 vitreous, or red and ferruginous, or a kind of blue hornstone, — the 

 gneiss often like the finer varieties below. The largest fragment I 

 saw measured sixteen inches long, by nine broad, and seven thick ; 

 but the generality are much smaller. In no place could I find any 

 granite in this breccia. Above the breccia coarse gritty beds occur, 

 interlaminated with finer materials ; some of them almost a light-red, 

 fine-grained quartzite. The breccia is everywhere exceedingly hard, 

 and in many places closely resembles the gneiss ; so that the broken, 

 turned-over ends of the gneiss appear to pass almost imperceptibly 

 into the sandstone. On the outer headlands, the red sandstone dips 

 to the west or south-west, and forms a low undulating country, with 

 the outcrop of the beds projecting through the moor. On Loch 

 Maree the sandstone first appears as mere fragments of the coarse 

 breccia, stuck in among the ends of the vertical red or grey gneiss. 

 Near Talladale it becomes continuous, resting on, and as it were 

 embossed in the hollows of, the gneiss hills. In mineral character it 

 presents few peculiarities, except that a false bedding or lamination is 

 not uncommon. From the uneven surface of the beds and the low 

 angle, the dip is uncertain, but is about 10°-15° to S., 25° to 30° E. 

 In the mountains on the south-west of the lake, the white vitreous 

 quartzite is clearly seen overlying the red sandstone, and often 

 projecting in a kind of terrace on the side of the hill. In some 

 of the lofty summits near Ben Eay, darker beds again rest on the 

 quartzite, perhaps the equivalents of the grey siliceous beds of Loch 

 Broom. 



The red sandstone in this district has undergone enormous denu- 

 dation. On the shore of Loch Maree it is often broken up into huge 

 masses, or divided by gaps and fissures, some of them still twenty to 

 thirty feet deep, though only a few (10 to 20) inches wide. The 

 surface of the beds, too, is strewed with immense angular and ruin- 

 like blocks, some of them poised on a single corner on the very edge 

 of a cliff. All this indicates extensive destruction of the strata ; and 

 other proofs of the fact are not wanting. Detached fragments of the 

 breccia are found in hollows of the gneiss hills far from the main 

 masses, and evidently left in the general denudation. Several of 

 these fragments appear on the shores of Loch Maree, and many of 

 the beautiful wooded islands sprinkled over its surface are of the 



