Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/431

1869.] JOASS-SUTHERLAND GOLD-FIELD. 321 intervals up stream, alternating with softer gneissose rocks and micaceous schists, with an occasional thin bed of white felspathic rock, c. Here gold is found in small scales by washing the overlying drift, which consists of a dark blue clay, containing rolled fragments of red granite and quartz, and is overlain by yellowish clays, gravel, and sand, all apparently arranged by running water. The lower part of this stream runs through shingle, and finally between steep banks of black alluvium, till it enters Loch Brora. Falling into this loch from the north-east, Allt-Smeorail, or the Gordon-bush burn, emerges near the road from a deep ravine, where the rocks are well displayed. These dip E. and S.E. at a high angle, and consist of flaggy quartzites and micaceous beds, with associated granitiform rocks, red and pink, among which are b and c, and a few quartz-veins. The granites never flex the neighbouring strata; the quartz-veins occasionally do. The gritty drift, or gold-wash, is here overlain by reddish-clay and sand, derived apparently from the detritus of Beinn-Smeorail, a conglomerate mountain capping unconformably flaggy quartzose and gneissose beds. Old-town and Clais-mor burns, both tributaries of the Brora from the east, run through red boulder- clay and over Old Red Sandstone, which is the underlying rock, to the junction with the Clyne Oolite. No gold was found in either of these two streams.

The Coast.

A very small quantity of gold was found at the head of the Clyne-Millton burn to the eastward, where flaggy quartzites occur. Kintradwell burn runs in a deep ravine cut through yellowish boulder- clay. The channel is almost covered by boulders of granite and sandstone; but a small section of a rock in situ shows flaggy gneiss dipping E.S.E. Allt-Choille is a deep and rugged ravine, the lower part of which is cut through boulder-clay and soft oolitic sandstone. Near the bridge the rocks are highly indurated and quartzose, containing carbonate of iron in thin seams and drusy cavities. No gold has been found either in Kintradwell or Allt-Choille.

Glen Loth.

The Loth-beg Water runs its lower course over a red porphyritic granite, resembling that of the Ord. In Sletdale burn, a tributary from the west, a few flaggy gneissose rocks are seen above the bridge dipping E.S.E. The course of this stream, in its upper reaches, is over gravel and through peat moss, concealing the junction which here takes place between the Lower Silurian and Old Red Sandstone.

On the shoulder of the hill which bounds the opening of Glen Loth to the east, large-grained porphyritic granite crops out, in many places highly ferruginous. This rock is believed to persist to the Ord of Caithness, as it is visible at intervals along the hillside, and forms the bed of the Culgower burn and the mountains that overhang the opening of Strath Ullie or the Helmsdale valley.

Pursuing the course of the Glen-Loth stream upwards, the rocks, where visible in the escarpments of the lofty mountains to the left,