1883. 9 Trans. N. Y. Ac. Sci. 
prove the opportunities thus brought, as it were, to his very door; and 
he soon began to find implements in these railroad cuttings, of the 
same style of material and of workmanship as those previously found 
in the river bluffs. There was now no possible doubt as to the impor- 
tant fact that rude palzolithic implements are truly contained in, and 
throughout, this dark stratified gravel of the Delaware valley, and 
that they furnish probably the earliest traces of man in eastern North 
America. 
The most interesting part of the problem, however, yet remained to 
be solved. Of the facts there was no question. Implements of pecu- 
liar type, large, rude, and wrought from a hard, compact argillite, are 
characteristic of, and confined to, this gravel. The gravel bears the 
clearest evidence of its deposition from flowing water, the cross-bed- 
ding, etc., being frequently very finely displayed; and its well-rounded 
stones and pebbles have the flattened form distinctive of river wear, 
and are derived from the rocks higher up the Delaware valley. But 
when was this deposit formed, and what relation does it bear to the 
geology of the region ? 
It was impossible not to connect these paleolithic gravel-beds with 
the great Ice age; and Dr. ABBOTT, as above stated, had already done 
so, judging the deposit to date from the vast flood of cold water that 
poured through the valley of the Delaware during the time of the melt- 
ing of the ice-sheet of the true Glacial period. Of course, this carried 
back the human occupancy of the country to a very remote antiquity. 
At this stage of the investigation, a somewhat related, but wholly 
independent, series of observations was begun and carried on by Prof. 
H. CARVILL LEWIs, of Germantown, Penn., in connection with the 
Geological Survey of that State. Dr. ABBOTT’S work had been prop- 
erly archeological, and chiefly confined to the local deposits at and 
near Trenton. Prof. LEWIs, on the other hand, took up a line of ob- 
servation strictly geological, and ranging over a wider field, in the 
study of the surface-deposits of Eastern Pennsylvania. It now appears 
that facts have been developed in this way that could not have been 
gained from the Trenton region alone; and thus these two accom- 
plished workers have supplemented each other’s results, and conclu- 
sions have been reached which rest on independent, yet concurrent, 
evidence. 
In the Old World, the distinction has long been familiar to students 
of ancient glacial phenomena, between an earlier and a later Ice-period, 
—the first, a great continental prevalence of arctic conditions, with a 
general movement of the ice-sheet southward ; and the second, a less 
extreme and extended development of cold, showing itself, however, 
in local glaciation, in which all highlands and mountains became cen- 
