1900-1901. | A Geological Trip. Hy 2 
denudation previously referred to, the smooth rounded ap- 
pearance it now has being impressed upon it by severe glacia- 
tion in the Ice period. Where the rock has been exposed to 
recent. prolonged denudation it breaks up into wild crags, as 
can be seen on the west coast line. Geikie describes gneiss as 
a schistose aggregate of orthoclase, quartz, and mica, with bands 
of hornblende schist, actinolite schist, mica schist, &c., and 
varying in texture from a fine-grained rock up to a coarse 
crystalline mass. Plate XIV. 2 gives a hand specimen, 
showing but little sign of foliation. A banded specimen is 
shown in Plate XV. 1, the dark bands being composed of horn- 
blende or some allied mineral. 
The second diagram (fig. 2, B) shows the levelled platform 
of gneiss being gradually submerged, and being covered, as it 
sinks, with a series of rocks composed of conglomerates and 
fine sandstones, in layers, and of great thickness, some 
thousands of feet. These are the Torridon sandstones. From 
their general appearance they must have been accumulated at 
a fairly rapid rate, as broken and not much weathered crystals 
of felspar are frequent. They probably represent an extensive 
lacustrine deposit. No distinct fossils have yet been found. 
The sandstones contain many pebbles derived from the gneiss 
itself, and also many of quartzite, &. Plate XV. 2 is a 
specimen obtained from the base of the series on the shore of 
Loch-an-Fada, on the slopes of Suilven. After these sand- 
stones had obtained their full thickness the land rose again 
above the level of the water, was bent into gentle folds so that 
the sandstones were tilted at low angles to the horizontal, and 
the whole mass was subjected to an enormously long period of 
denudation, during which, over wide areas, the sandstones were 
completely removed from the underlying gneiss. Subsidence 
again took place, and we see, as in the diagram fig. 2, C, the 
tilted and denuded ends of the Torridon sandstones, and the 
exposed gneiss being overlaid by a great series of rocks, which 
lie unconformably along the upturned edges of the tilted sand- 
stones. The internal evidence afforded by this fresh series of 
rocks points to the conclusion that the subsidence was more 
rapid this time, and carried to a greater depth. The first 
layer, basal quartzite, is composed of a rough quartz con- 
glomerate (Plate XIV. 3), 200 to 300 feet thick. Above this 
