Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/178

84 escarpment C. The beds below c are stratified clays, sometimes mottled, and are said to repose on the lower gravel. This lower gravel is said to be 3 ft. thick; and at 45 ft. from the surface the chalk is said to be found near D; but I have not seen this myself.

Some years since, an excavation was made near M, and chalk was found about 43 ft. from the surface. The false-bedded sands were 20 ft. thick at that point, and covered the upper-gravel series, e, very full of flints and pebbles.

The Mammalian remains occurring in the gravel, f, are more rolled than those found in the brick-earth above.

A list of Grays species has been published by Prof. Morris, and also in the Geological Society's Journal, vol. xxii. p. 101, by Mr. Boyd Dawkins.

Returning to Pl., IV. fig. 6, the false-bedded sands are represented thinning out towards the river, as well as the Cyrena-beds. The depth of the chalk below the surface is ascertained by a well-section at F; and the covering gravel, e, comes in contact with the lower gravel, f, near the railway-cutting, g. Close to this point there was a section of coarse gravel, 12 ft. thick, open in a gravel-pit, reposing upon chalk without any beds of sand or brick-earth. The chalk is said to have been seen in the railway-cutting 9 ft. above the rails at the bridge I. In the tramway east of, and close to, Grays Station, the chalk is also well exposed 6 feet above the rails, with thick beds of gravel lying irregularly upon it, and some brick-earth beds and gravel above them containing comminuted shells derived from the Woolwich series, which beds have been entirely removed by denudation at Grays. In excavating for a cellar near Grays church, a very large mass of sandstone was found about 20 ft. above the Ordnance datum-line, many tons in weight, in the gravel close to the chalk. Such stones are abundant in the upper gravel in the Chalk and Thanet Sand west of the Grays Station.

Great changes have taken place at Grays, by removal of brick-earth, since Professor Morris first described the fossils from the Thames-valley deposits;and he is almost the only geologist who has watched the excavation from year to year. It will be seen from Pl. IV. fig. 6, that, like the gravels of the Somme, the fossiliferous brick-earths of Grays are deposited in a concavity of the chalk. The chalk is 15 ft. lower at D than at G, and 43 ft. lower at D than B. The old Thames river seems to have divided into two channels at Grays; and the fluviatile deposits between C and G appear to have occupied one channel, thus forming the whole series of stratified beds which are intercalated between the gravels e and f.

The last deposit was the covering gravel-bed, e, which is continuous from themarsh to the point A, and beyond it.

The position of the section (Pl. IV. fig. 7, Erith) A B S T is laid down on the sketch map, Plate IX.; and A B, the part near the escarpment of the Chalk and Thanet Sands, is enlarged in fig. 17. page 85. Although Erith and Grays are not exactly opposite each other on the Thames valley, yet the sections, Plate IV. figs. 6 and 7,