Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/255

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245
Mr. Webster on the Strata lying over the Chalk.

stratum of London clay, but always upon it, and frequently accompanied by marl and freshwater shells.

Other bones of ruminating animals, as those of the horse, ox, and stag, not different from the living species, are frequently dug up at small depths, and are covered by peat, gravel, loam, &c.

In the freshwater formations of the basin of Paris the bones of terrestrial animals are found, which do not belong even to known genera, and many of those found near the surface in their alluvium, belonged also to animals of great size, and which are now found only in countries very remote.

We see therefore that a similar succession of animals has lived in this portion of the earth, during the various stages of its habitable state.

V. Concluding Observations.

One of the most interesting consequences deducible from the above examination of the last formed strata of this country, is, perhaps, the view which it seems to afford us, of establishing, in some degree, a series of epochs between the deposition of the chalk strata and the formation of the present surface of the land; not indeed to be distinguished by computable time, since no date can be affixed to any of the changes to which I have alluded, but an order of succession of the great events at least appears more than hypothetical, which it may be useful still further to consider.

The origin of the calcareous matter of which the chalk formation is composed remains one of those hidden mysteries on which all the speculations of geologists have not thrown any certain light.

In the several strata of chalk however, although their sources were probably not very different, we may perceive several circumstances which indicate the action of modifying causes in each deposition,