Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/199

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189
Mr. Webster on the Strata lying over the Chalk.

below Christchurch, is well known, on account of its fossils, which are found in a very perfect state. They have been collected and very accurately described by Mr. Brander and Dr. Solander.

At Stubbington, a few miles west of Portsmouth, the same stratum of blue clay with much green earth is visible, in a low cliff, with the same fossils as at Alum bay and Hordwell: the strata being horizontal. The fossils here, as at Alum bay, though numerous, are in a very fragile state; minute nummulites are extremely abundant.

Portsmouth is built upon this stratum, and several deep wells sunk there afford us much information. James Hay, Esq. F.L.S. kindly furnished me with the following account of the sinkings at that place.

“1. Vegetable mould.

2. Yellow loam, of which excellent bricks are made.

3. Yellow gravel, composed of rounded siliceous pebbles and sand, from 4 ft. 6 in. to 10 feet thick. In some places, towards the bottom, the sand abounds; and, generally, within a few feet of the blue clay, is very fine, and in many places is of a greenish colour. In the yellow gravel are found many organic remains, siliceous, and all rounded by attrition. In a few instances singular bones have been discovered.

4. An immense bed of blue clay, which in many places at the surface is mixed with sand strata. At the depth of 30 feet it is traversed by a thin stratum of white pebbles. Many wells are dug to this stratum, which contains water, but of a hard quality. At the depth of 60 feet another similar stratum is found, containing water also, and of a softer quality. No wells had been sunk lower than this last stratum, until within 15 years ago, when a well was dug in the Dock Yard, to the depth of 202 feet. Excellent