that in 1861 Professor Prestwich followed up his “notes on further discoveries of flint implements in beds of post-pleiocene gravel and clay,” with a list of forty-one localities where gravel and clay-pits, or gravel-beds occur, as some of the places in the south of England where he thought flint implements might also by diligent search possibly be found, and subsequent discoveries have confirmed his anticipations. It has been felt by many as an element which in some degree detracted from the otherwise incontrovertible force of this accumulated proof, that where the wrought flints are discovered _in situ_, they occur in beds of gravel and clay abounding in unwrought flints in every stage of accidental fracture, and including many which the most experienced archæologist would hesitate whether to classify as of natural or artificial origin. But on the assumption of regular quarrying and working in the flint-bearing strata, such traces of palæolithic art may be expected to occur in the river-gravels, as a geological formation in which the requisite material abounded; and which, moreover, in its latest reconstruction belongs to the river-valleys best adapted to be the habitat of post-glacial man. They are, in fact, the localities to which the experience of the archæologist would direct him when in search of the traces of rude hunting and fishing tribes; but also they are the same mammaliferous strata to which the geologist turns when looking for remains illustrative of the extinct fauna of the post-glacial age. [Illustration: FIG. 5.—Lanceolate Flint, Flint Ridge, Ohio, (2/3).]