bank or the collection, ten per cent to thirty per cent exhibit unmistakable traces of design, a somewhat larger percentage suggest but do not prove design, and not more than fifty per cent strike the student as natural, when the individual specimens are examined separately; and when examined collectively the correspondence in form and mode of fracture between symmetric "turtle-backs," "failures," "spawls," "chips," and miscellaneous fragments compels the cautious geologist to question whether any are demonstrably or even probably natural: the series is not from the certainly natural to the doubtfully artificial, but from the certainly artificial to the doubtfully natural.
The "turtle-backs" tell nothing of the customs of the makers, since their function is unknown; whether they were sinkers for nets, whether they were hammers or axes used either in the hand or attached to withes or handles, whether they were used as the bolas of the Patagonians, whether they were employed in fishing first for cutting the ice and then for eviscerating and scaling the fish, or whether they subserved a variety of purposes, remains undetermined. The environment read from geology indicates that the Trenton man was a hunter or fisherman who used and lost the primitive tools of his mysterious craft within the waters rather than upon the land, and thus appears to materially narrow the range of hypothesis as to his activities; but the extravagance in labor indicated by the vast numbers of unworn implements suggests that the rapid modification in environment and occupation accompanying the ice-invasion outran the resulting modification in appliances, and that the implements were really invented on land and were but ill adapted to the new conditions; and the introduction of a new type of implement during the brief epoch of gravel deposition gives support to the suggestion.
So the margin of the cloud enveloping the beginnings of human life in America is slowly lifting. Already there is definite and cumulative evidence of man's existence during the latest ice epoch, with a strong presumption against an earlier origin than the first Quaternary ice-invasion; already it is known that the primitive American haunted the ice front rather than the fertile plain, and must have been hunter or fisherman; already his environment is so well known as to partially elucidate his activities; but the first traces of the autochthon yet found tell of an intelligent being who dominated the animal world as does his descendant, and thus the mystery of man's ultimate origin remains enshrouded as darkly as ever.