202 
red gravel (Champlain or Palaeolithic epoch) ; 7. Philadelphia 
brick-clay (same date) ; 8. Trenton gravel (equivalent to the 
Reindeer period of Lartet). 
Mr. Lewis remarks : — 
“It is thought that the hypothesis of a second and more 
local glacier, long subsequent in age to the first great glacier, 
will explain all the facts observed. The Trenton gravel 
cannot be assigned to the First Glacial period except by assum- 
ing that there have been no river gravels deposited since that 
time, — an assumption that can hardly be maintained. Some 
European archaeologists have held that the Palceolithic era, 
the era of the river gravels, is antecedent to the Reindeer 
period, the period of the Cave-men. No such distinction has 
been observed on the Delaware. The period of the Trenton 
gravel flood, whether contemporaneous with a glacier or not, 
is the period of the last geological deposits here known ; the 
recent mud-flats being alone excepted” (p. 13). 
With regard to the age of the Trenton gravel, he says : — 
“ The same reasoning that showed that the modern river 
channel might have been excavated in hundreds rather than 
in thousands of years, will indicate that no great length 
of time is necessary to produce all the surface features 
of the Trenton gravel. While the writer may venture to 
express the opinion that there is no reason geologically for 
carrying the age of this gravel and the antiquity of man on 
the Delaware farther back than a very few thousand years at 
the most, he is fully aware that any close approximation can 
safely be arrived at only by extended comparison with other 
river gravels and by a much more complete series of obser- 
vations than has yet been possible” (p. 15). 
If Mr. Lewis is correct in his reading of the sequence of the 
geological phenomena in the Delaware valley, and in his con- 
clusion that the gravels in this region are of different epochs, 
it corroborates a conjecture made by me elsewhere with 
regard to the European river gravels, and I shall not be sur- 
prised if a more careful study of the European beds shall show 
that the gravels in which the so-called palaeolithic implements 
have been found are the newest and latest in a series of beds 
running back into pre-glacial times. 
