Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/749

1870.] have. It is difficult to conceive that a river flowing with the velocity due to such a fall could have spread out the gravel over these wide even surfaces more than 20 miles across; and the various directions in which the tablelands slope forbid the supposition that any part of the present inclination is owing to a subsequent tilting up of the land.

It is perhaps a more probable hypothesis that the spreading out of the gravel and the levelling of the plains took place in an inlet shut in on the south by high land and opening out to the eastward. If this were the case, the land at the time of the deposition of the highest gravels now remaining must have stood 420 feet lower; and this may have been in some degree contemporaneous- with the great depression of the Boulder-clay epoch. A deposit thus formed of materials brought down from the chalk country on all sides would be entirely local in character; but the apparent absence of indications of glacial conditions in the gravel, except at levels so low as to correspond with valley-gravels, is not easy of explanation.

(d) The raised shingle of the Foreland, the marine gravel of the south of Sussex, and the beach-deposits with sea shells at Avisford and Waterbeach are evidences that at a time geologically recent the land stood 80 or 100 feet lower. Flint implements, however, are found imbedded in gravel 120 feet above the sea on the Bournemouth cliffs, and 150 feet above the sea on Southampton Common; and an hypothesis which assumes that man existed when gravels, now 120 and 150 feet above the sea, were forming at or below the sea-level may be on that account alone considered as untenable. But flint implements are found at Menchecourt associated with marine shells at 40 feet above the sea, and at the Foreland under circumstances which seem to show that an elevation of land to the extent of from 70 or 80 feet has taken place since man's appearance; and when it is considered what an enormous amount of change has taken place at Salisbury and elsewhere since the high-level gravels containing flint implements were deposited, and what a vast amount of time such changes imply, it does not appear to be incredible that the upheaval should have been so much as 150 feet.

A considerable alteration in the coast-line must also have taken place. Land must have existed to the south of an inlet such as that supposed, of which the Isle of Wight is but the shadow. Denudation of the surface by subaerial action, and of the coast by the sea, must have gone on pari passu with upheaval ever since the high plains were first raised above the sea-level. As the land gradually rose, the effect would have been to contract the inlet and bring it into the condition of an estuary branching into the Solent and Southampton Water. Of these, the latter remains an estuary, while the