Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/180

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Mr. Webster on the Strata lying over the Chalk.
  1. Marl with freshwater shells.
  2. Dark blue clay without shells.

These must be placed between the alluvium and the London clay, of the former list.

In the subsequent pages I shall describe more minutely the form of the basin of the Isle of Wight; and also that of a similar basin on which London is placed. I shall enumerate the strata and principal organic remains contained in each, and conclude by pointing out such circumstances of agreement or difference as I have been able to observe between them and the Paris basin.

II. Extent of the Isle of Wight Basin.

In tracing the margin of the cavity in which these horizontal depositions of the Isle of Wight are found, I shall begin with the south side.

The middle range of chalk hills in this island, together with the other highly inclined strata of Alum bay, form part of the ancient border. If we sail west from the Needles in the Isle of Wight, to Handfast point in Dorsetshire, we shall find that this vertical chalk range again makes its appearance in that coast, and may be traced thence through Corfe Castle to some distance beyond Lulworth; and from the correspondence in the line of direction of the Isle of Wight hills with those of Dorsetshire, and the general agreement in the position and nature of the strata, (the section of the Isle of Purbeck corresponding nearly to that of the Isle of Wight,) it appears extremely probable that at some former period these places were united.

The clay however over the chalk, and part of the chalk itself,