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 confirmed his anticipations. It has been by the application of the same principle to the drift and river-valley gravels of the New World that a like success has been achieved. The result of a careful study of the tool-bearing gravel of the Delaware may be thus summarised from recent reports of trustworthy scientific observers. The Trenton gravel is a post-glacial river deposit, made at a time when the river was larger than its present volume. It represents apparently the latest of the surface deposits of the upper Delaware valley;[54] and Dr. Abbott remarks of it: “The melting of a local glacier in the Cattskill Mountains would probably result, at the headwaters of the Delaware, in a continued flood of sufficient volume, if supplemented by the action of floating ice, to form the Trenton gravels.”[55] But these gravels are now recognised as the youngest of the series of ancient implement-bearing deposits. Underneath lies the older Columbia gravel, which has also yielded—though in much fewer numbers,—palæoliths of primitive types. The researches of Mr. Hilborne T. Cresson in the State of Delaware have already been referred to; and from those results, as well as from similar disclosures in Ohio and Indiana, it is no longer doubted that reliable traces have been recovered of American man contemporary with the mammoth and the mastodon; and—like the old cave-dwellers of Cro-Magnon,—a hunter of the reindeer in the valley of the Delaware.