long as compared with, that marking the transitory stages of human development, and must give place to the still more precise chronometer afforded by the brief and sharply defined climatal episodes of later geologic time; the human records of diverse regions can only be correlated in terms of these brief episodes; and in ascertaining the relations of paleolithic man to the two best known climatal episodes of the past, it is immaterial whether these be called Tertiary or Quaternary. It is the special merit of the graphic method that it exhibits quantitative relations (for while verbal language is commonly qualitative, graphic language is always quantitative); and in the present case it affords a means of measuring the consistency of the evidence, and of instantly detecting the inconsistent records, of human antiquity.
There are several well-authenticated discoveries of human relics in this country in geologic deposits whose places may be fixed in the graphic time-record forming Fig. 1. Aughey records two chipped implements from the loess of the Missouri Valley, one of them coming from immediately beneath an elephantine vertebra; Miss Babbitt has found great numbers of quartz-chips in a Champlain terrace of the Mississippi at Little Falls, Minnesota, which are regarded by many archæologists as unquestionably artificial; N. H. Winchell records polished stone and copper implements as well as human bones from the same aqueo-glacial terrace of the Mississippi near Minneapolis; Belt several years ago found a fossilized human skull in what appears to be the westernmost extension of the loess in Colorado; Gilbert has shown that the geologic position of an ancient hearth found in excavating a well in northern New York indicates that it was constructed during the closing episodes of the last glacial epoch; a few years since McGee discovered a chipped obsidian implement imbedded in the upper lacustral marls of western Nevada; McAdams notes the finding of a stone axe in loess seventy feet beneath the surface in Illinois; and among the most recent and satisfactory archæologic discoveries of this country are those of two chipped implements of black flint found in Ohio by Dr. C. G. Metz, at Madisonville and Lovelands respectively, in deposits of loess and aqueo-glacial gravel which G. F. Wright has shown to represent a closing episode of the later glacial epoch. But it is in the aqueo-glacial gravels of the Delaware River at Trenton, which were laid down contemporaneously with the terminal moraine one hundred miles farther northward, and which have been so thoroughly studied by Abbott, that the most conclusive proof of the existence of glacial man is found; and it is here, too, that the most satisfactory evidence is obtained concerning the conditions by which paleolithic man was surrounded. It is significant that in all these cases