1883. 



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 raihoad 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 palaeolithic 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 archaeological, 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- 



