Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/813

Rh fulfilled in two ways—(1) the coast may have been more distant at the time when the stream ran at its higher level; (2) the sea may have stood at a higher level upon the present, or nearly the present, coast. Of the two it is most probable that the condition which allowed of the deposition of the terrace-gravels was the former, under which a lesser gradient may have coexisted with even higher land; for it is generally believed that this island then formed part of the continent of Europe; and the Pleistocene mammalian remains constantly dredged off our east coast point in the same direction.

But not only must the sea-coast have been further off, but the land must have been also higher, not merely less denuded down, but physically lifted up in relation to the sea-level; or, what amounts to the same thing, the sea must have been lower. Otherwise we cannot account for deposits on the sea-level, and even below high- water mark, such as occur at Clacton and at Walton-on-the-Naze, and on the dredging-grounds in Essex—the former being, according to Prof. Dawkins, one of "the first terms of the Postglacial series," the latter having nothing to separate it from a somewhat early postglacial deposit.

If this supposition is correct it will rather militate against the opinion of Prof. Seeley, which is referred to by Mr. Jukes-Browne, that the marine gravel of March is of the age of the Barnwell gravels. The coast at the time the latter were deposited ought to have been more distant than March is.

As regards the climate at the period of the Barrington deposit, the occurrence of Elephas antiquus and Hippopotamus point to a somewhat warm climate. The Elephants and Rhinoceros being the same as at Lexden, in Essex, and the gravel terrace of about the same altitude, it is likely the gravels are of the same age. At that place the remains of beetles, which are abundant, have been attributed by Mr. Wollaston to a warm climate, probably Mediterranean. The Unio and Cyrena of Barnwell have a like significance; and Helix nemoralis is impatient of great cold.

We learn, then, that there was an interval since the Glacial period (for there is no question that both Barrington and Lexden deposits are Postglacial) when the climate of this island was somewhat warmer than it is at present. There are indications in the disappearance of Elephas antiquus and Rhinoceros leptorhinus, as well as of Cyrena fluminalis and Unio litoralis, that it became afterwards colder, and probably colder than it is now; and my own belief is that a still colder period supervened, which is evidenced by the mechanical accumulation of that drift covering which I have denominated "trail".