Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/201

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191
Mr. Webster on the Strata lying over the Chalk.

forming to the west of the river a hill, the greatest part of which is now destroyed by the action of the sea. At this place the chalk is about 50 feet in height, and is covered immediately by a bed of sand 20 feet thick. Over this are thin strata of yellow marl and clay, containing a coal much resembling that of Corfe and Alum bay. H. Warburton, Esq. Secretary to the Geological Society, who first noticed and pointed out to me these interesting strata, found impressions of leaves in the marl which exactly resemble those engraved in one of the plates of the Essay on the Mineralogy of the Environs of Paris: and I have since recognised among the specimens brought from that place, a fruit of one of the palm tribe, with the vegetable fibres quite distinct. Shells belonging to the Genera Cerithium, Cytherea and Ostrea, together with pyritous casts of the same, also occur.

With this coal are found thin masses of gypsum both selenitous and fibrous; and over all is a thick bed of blue clay with marine fossils, which are different from those usually found in the London clay.

It was here that I found the singular substance which the experiments of Dr. Wollaston ascertained to be a new mineral, a subsulphat of alumine. It lies immediately upon the chalk, and fills up a hollow in it. About a mile on the east side of Newhaven the chalk cliffs rise again to an equal height and continue to Cuxhaven, where there is a similar interruption, and thence extend to Beachy Head, increasing regularly in altitude, and forming tremendous precipices of several hundred feet in height.[1] The chalk here is covered only by a thin layer of sand and gravel.

  1. One of these prodigious falls of the chalk cliffs, which make a residence near them frequently so dangerous, occurred a few days before my visiting this spot, accompanied by a remarkable circumstance. The clergyman of East Dean, who was walking near the brink of the precipice, perceived the ground to give way under him, and had the