Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/262

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Mr. Webster on the Strata lying over the Chalk.

The strata are situated in the department of the lower Rhine, in the mountains of St. Sebastian, one of the lowest in the chain of the Vosges.

The great quantities of white calcareous marl with freshwater shells, so frequently found on the top of the London clay, and enveloping the bones of land animals, would seem to denote a marshy country, and one containing a great deal of stagnant water. This seems to have been the first state of the country at the time of the emerging of the land after the deposition of the blue clay.

In this marl and over the clay is the first appearance of land quadrupeds, agreeing in this respect with the same observation made by Cuvier on the calcaire grossier, above which in France their remains are found in abundance.

The changes preceding or accompanying the upper marine formation perhaps destroyed part of the superior strata, and deposited many of those extensive beds of shells now to be found over the London clay. But the nature of the last original marine strata of this country, the revolutions they may have undergone even in the ancient state of the earth, are circumstances which can probably no longer be explained.

Whether the existence of the second freshwater formation in the Isle of Wight will admit of the same solution as has been proposed for the first, must be left, like it, undecided: but it appears to have taken place in a lake possessing the utmost tranquillity.

Upon the whole it must be allowed that the points of resemblance which have been enumerated between the superior strata of this part of our island and the adjoining part of the continent, are too numerous and striking to be the result of accidental causes, and demonstrate in the clearest manner that they were occasionally subjected to the same general laws. Whilst at the same time the variations are so considerable, that the effects of these causes appear to have been much modified by local circumstances.