Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/218

 As examples that may be easily examined, I may cite a section on the Dufftown Railway, at the Popine meal- and saw-mill, near Lower Craigellachie, also the rock at Craigellachie Bridge, and along the side of the Fiddich from Craigellachie Station to near Kininvie Castle. The rock of the hill called Upper Craigellachie near Aviemore, is also of a similar nature, so that in many places I should be at a loss to say whether the granite or the gneiss prevails. Along the Fiddich, from Craigellachie Station to near Kininvie Castle, the rock exposed in the railway- cuttings is a hard quartz, so full of veins that one is occasionally in doubt whether to pronounce it a stratified rock or a granite. In many places, where the aggregation of the mineral particles is granitic (rather small-grained and reddish), traces of the undulating bedding may be observed ; in short, the rock seems to me to consist of the beds of lower quartz-rock merging into granite — that is to say, incipient granite, a stratified rock far gone on its way to granite.

In some places, near Craigellachie, there is a good deal of greenish matter in the rock, as if it had consisted of alternations of talcose schist or grit and quartz-rock, such as occur near the base of the slate on the Mulben stream, and also near the Giant's Chair, where the upper beds of slate meet the overlying quartz-rock. I observed that the small granite veins occasionally form alternating laminae in the rock, and reddish streaks parallel to the bedding, the greenish matter segregating into irregular branching plates.

The hill called Little Conval, near Dufftown, is of granite, which at its south-eastern base I found to be large-grained and composed of red felspar and whitish quartz, with little or no mica ; but higher up the rock becomes finer-grained, and at the top consists of a small-grained mixture of red felspar and quartz, much resembling some varieties of quartzose gneiss, such as that at Red Hythe Point, as if the metamorphism decreased in intensity as it passed upwards. The felspar, however, is redder than is usual in gneiss, and seems to bear a larger proportion to the quartz. There are the remains of an old stone rampart or enclosure round the crest of this hill.

Theory of the Derivation of the Sedimentary Strata and of their Present Strike.

The general texture of the materials of which the gneiss, quartz- rock, and clay-slate are composed is fine-grained, and I observed no beds of conglomerate or large pebbles. The nearest approach to these which I saw was in the coast-section between Gamrie Head and Melrose, near a place called the Grey Mare's Point, where the anticlinal fold occurs that is shown in Prof. Harkness's section. Here I observed a seam composed of water-worn pebbles of white quartz, some of which were two inches in length. This is near the base of the slate, and is the nearest approach to a conglomerate that I have observed. But in general there is nothing larger-grained than what, in its original condition, would have been a coarse sand. It is a curious circumstance that such a thick mass of sediment