through a deep railway-cutting, the rails being 80 feet below the surface of the ground, and 112 feet below the adjoining peak of rock at D.
The escarpment of rock is shown to slope about 43° N., at the northern end of the cutting, B, close to the viaduct, and only about 20° at the southern end, D. Gravel with boulders of Old Red Sandstone, and many other rocks, is spread over the surface of the rock at D, up to a height of 200 feet above the river Taff.
Fig. 4.—Enlarged Section of Gravel Deposit.
Fig. 4 is an enlarged view of the section at B along the line of railway, showing the gravel lying in a concavity of the rock forming a part of the Taff valley, at very high angles. Near the rock the dip of the gravel is 35°, gradually becoming less steep until it reaches 18°. The gravel below the rails is not exposed at this point. It will be seen that fig. 4 should have been reversed, to accord with P1. IV. fig. 1; it is on the natural scale.
Fig. 5.—Section across the Taff-Valley Railway.
Fig. 5 is a transverse section at right angles to Plate IV. fig. 1, and fig. 4, showing the railway-cutting at the point D. As it is not sloped, it gives a good opportunity of studying the position of the gravel, particularly as the surface of the rock is clearly exhi-
