56 DR. DANIEL WILSON ON 
its larger pebbles, and possibly stone implements of late origin, upon the gravel of the new 
bed of the stream.” But after giving every legitimate weight to such probabilities, expe- 
rience has satisfied him that there is no difficulty in separating chance-buried neolithic or 
modern implements from the genuine palæolithic celts or hatchets abundantly present in 
the undisturbed gravel beds, from which they have been takeu on their first exposure. 
The importance attached to the recovery of the turtle-back implements in undisturbed 
gravel-beds has received full recognition ; and it cannot admit of doubt that repeated discov- 
eries have now been made under circumstances which prove them to have been a consti- 
tuent part of the gravel, and not intrusive objects. Professor Henry C. Lewis, of the 
Pennsylvania geological Survey, in discussing the age of the Trenton gravel, remarks :— 
“At the localities on the Pennsylvania Railroad where extensive exposures of these gravels 
have been made, the deposit is undoubtedly undisturbed No implement could have come 
into this gravel except at atime when the river flowed upon it, and when they might have 
sunk through the loose and shifting material. All the evidence points to the conclusion 
that at the time of the Trenton gravel flood, Man, in a rude state, with habits similar to 
those of the river-drift hunter of Europe, and probably under a climate similar to that of 
more northern regions, lived upon the banks of the ancient Delaware, and lost his stone 
implements in the shifting sands and gravel of the bed of that stream.”* Notwithstanding 
the revolutions that time has wrought, the locality retains sufficient indications of its 
ancient characteristics to satisfy the experienced eye of its fitness to have been the habitat 
of a race of primitive hunters and fishers. “It is evident,” says Dr. Abbott, “that at just 
such a locality as Trenton, where the river widens out, traces of man, had he existed during 
the accumulation of the gravel, would be most likely to occur. This is true not only 
because there is here the greatest mass of the gravel, and the best opportunities for examining 
it in section ; but the locality would be one most favourable for the existence of man at the 
time. The higher ground in the immediate vicinity was sufficiently elevated to be free from 
the encroachments of the ice and water, and the climate, soil, and fauna are all such as to 
make it possible for man to exist at this time, in this locality.” + The remains not only of 
the American bison, but of the extinct mastodon, occur in this gravel. Professor Cook, the 
State geologist, in his report for 1878, describes the tusk of a mastodon found under 
partially stratified gravel at a depth of fourteen feet; and Dr. Abbott states that, within 
a few yards of this tusk palæolithic implements have been gathered, one at the same, and 
three at greater depths, from which he assumes the unquestionable presence of man on 
the Atlantic coast, contemporary with the mastodon and other extinct mammals of the 
drift. 
An inter-glacial age is no longer claimed for the primitive American tool-maker ; and 
though Dr. Abbott still maintains the glacial origin of the Trenton gravel, he no longer 
deems it necessary to claim for it a greater antiquity than ten thousand years. “It may 
be, indeed,” as Professor Lewis adds, “that as investigations are carried farther, it will 
result, not so much in proving man of any great antiquity, as in showing how much more 
recent than usually supposed was the final disappearance of the glacier.”t The date thus 


* The Antiquity and Origin of the Trenton Gravel, p. 547. 
+ Primitive Industry, p. 481. 
Ÿ Ibid, p. 551. 
ln 
