not been confined simply to subsidence, but have comprised oscillations in the level of the land, by which marine shells of the post-pliocene period have been raised some ten feet or more above the level of the sea.
Small as is the progress hitherto made in interpreting the pages of the peaty record, their importance in the Valley of the Somme is enhanced by the reflection that, whatever be the number of centuries to which they relate, they belong to times posterior to the ancient implement-bearing beds, which we are next to consider, and are even separated from them, as we shall see, by an interval far greater than that which divides the earliest strata of the peat from the latest.
Flint Implements of the Post-pliocene Period in the Valley of the Somme.
The alluvium of the Valley of the Somme exhibits no thing extraordinary or exceptional in its position or external appearance, nor in the arrangement or composition of its materials, nor in its organic remains; in all these characters it might be matched by the drift of a hundred other valleys in France or England. Its claim to our peculiar attention is derived from the wonderful number of flint tools, of a very antique type, which, as stated in the last chapter, occur in undisturbed strata, associated with the bones of extinct quadrupeds.
As much doubt has been cast on the question, whether the so-called flint hatchets have really been shaped by the hands of man, it will be desirable to begin by satisfying the reader's mind on that point, before inviting him to study the details of sections of successive beds of mud, sand, and gravel, which vary considerably even in contiguous localities.
Since the spring of 1859, I have paid three visits to the Valley of the Somme, and examined all the principal
