before us that even now the Stone period of its aborigines has not wholly passed away, careful observation is required in determining the probable age of stray specimens buried even at considerable depths. But disclosures of an actual American implement-bearing drift appear at length to have been met with in the valley of the Delaware. These show the primitive tool-maker resorting to a granular argillite, the cleavage of which adapted itself to the requirements of his rude art. Professor Shaler, in a report on the age of the Delaware gravel beds, describes this formation as occurring from Virginia northward to Labrador, though it is only in New Jersey and Delaware that the accompanying evidences of human art have been thus far recovered. The New Jersey drift is made up of transported material, including boulders and smaller fragments of granitic, hypogene, sandstone, and limestone rocks, along with water-worn pebbles of the same granular argillite as the characteristic stone implements recovered from it, to which, from their peculiar shape, the name of “turtle-back celts” has been given. There is little true clay in the deposit to give coherence to the mass. The type of pebble is subovate, or discoidal, suggesting its form to be due to the action of running water; and it seems probable that the stone was not quarried out of the living rock, but that the pebbles thus reduced to a convenient form were turned to account by the tool-maker. The researches of Dr. Abbott have been rewarded by the discovery in the drift-gravel of numerous examples of this peculiar type of implement, for which the one material appears to have been used, notwithstanding the varied contents of the drift-gravel in which they occur. As in the case of the French and English river-drift, the fractured material is found in every stage of disintegration. Professor Shaler says: “Along with the perfect-looking implements figured by Dr. Abbott, which are apparently as clearly artificial as the well-known remains of the valley of the Somme, there are all grades of imperfect fragments, down to the pebbles that are without a trace of chipping.” But more recent discoveries in the Delaware valley point to remains of a still earlier age than those described by Dr. Abbott. These naturally attracted attention to the region; for there, for the first time, the American archæologist saw a promise of disclosures corresponding in character to those of the European drift-gravels. A systematic and prolonged series of investigations accordingly carried out by Mr. Hilborne T. Cresson, under the direction of the Peabody Museum, have resulted in fresh disclosures of early American man. The Naaman’s Creek rock-shelter, carefully explored by him, is situated in the State of Delaware, immediately to the south of Mason and Dixon’s line. There in underlying deposits, claimed to be of Post-Glacial age, rudely chipped points and other implements, all of argillite, were found; and at a higher level, others