THE POPULAR SCIENCE MONTHLY.
ceeding glacial flood, more and more sand, gravel, and great bowlders were rolled down from the rock-ribbed valley beyond and spread upon the open plain through which the present stream unruffled flows.
The land was somewhat depressed then, and the water flowed at a higher level, but nothing unfavorable to man's existence obtained in the whole region. As a skilled geologist has pointed out, "The northern ice was one hundred miles away, and did not prevent primitive man from assembling about the low and hospitable shores of the miniature sea, . . . and over the bosom of the bay, little affected by tide because of its distance from the ocean, and little disturbed by waves because of its shoalness, palæolithic man may have floated on the simplest craft, or even have waded in the shallow waters." Ay! may have; but did he? What evidence is there that that most primitive of mankind, who left such abundant traces of his presence in the valley of many a European river, and also in Asia and Africa, was ever likewise here in eastern North America? It is precisely the same evidence—rude stone implements of the simplest type, often but slightly modified cobbles merely, that were found to be more effective by having a chipped and jagged edge, rather than the smooth and tapering one that water-wearing produces. These same worked stones in other countries always of flint, but in New Jersey of argillite, a slate-like stone that has been altered by heat, and possesses now a conchoidal fracture—these occur in the Delaware gravels; and the vivid pictures of glacial time, with primitive man a prominent feature thereof, that have been given by Wright, Wilson, Haynes, McGee, Upham, Cresson, Babbitt, and others, are doubtless familiar to all readers of recent scientific literature.
In associating man with ancient river valleys, we are too apt to think only of the stream, and ignore the surrounding country. Though largely so, palæolithic man was not strictly an amphibious creature; for instance, on each side of the ancient Delaware River extended wide reaches of upland forest, and here, too, the rude hunter of the time found game well worthy of his ingenuity to capture, and so powerful that all his wit stood him well in need to escape their equally determined efforts to capture him. While the seal and walrus disported in the river; while fish in countless thousands stemmed its floods; while geese and ducks in myriads rested upon the stream, so, too, in the forest roamed the moose, the elk, the reindeer, the bison, the extinct great beaver, and the mastodon, all of which, save the elk, had long since left for more northern climes when European man first sighted North America.
The association of man and the mastodon is somewhat start-