Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/187

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177
Mr. Webster on the Strata lying over the Chalk.

filled up with clay and loose chalk or marl: over this is another layer of pebbles, and again clay and chalk and fragments of flints; and these follow in succession, but very irregularly, to the top of the cliffs which is at least seventy or eighty feet in height. These materials are in general quite loose, being simply heaped or laid on each other; but sometimes masses of it are cemented together by stalactitical matter, and when the cliff falls, form blocks of great size and hardness.

It is impossible to see this cliff without immediately perceiving that it does not owe its existence to original stratification; but that it is simply the section of an immense heap of fragments of chalk and flints mixed with clay and sand, the whole of which has at some distant period been subjected to the action of water; and that it has been thus deposited upon the solid chalk stratum which is now seen below it.

In tracing this vast collection of water-worn materials, we find that it forms a considerable hill behind the town, and that it joins to the side of the range of hills called the South Downs.

In Alum bay in the Isle of Wight, however, the stratum immediately next to the flinty chalk, and consequently deposited upon it, consists of a white chalk marl without flints. Its nature is sufficiently shewn by its pulverizing with the frost; and the rains wash it down, so that its situation is marked by a deep hollow. There is some appearance here therefore of a transition of the last portions of the chalk into the clay which succeeded it; and, the usual rounded flint pebbles over the chalk and the other signs of disturbance being there wanting, it is possible that we have in that place the original succession of depositions. In many parts of Sussex also, south of the South Downs, as at Emsworth, Lavant, Siddlesham, South and North Bersted, Middleton, &c. I found

Vol. II.Z