308 PROCEEDINGS OF THE ACADEMY OF [1880. 



perhaps following a second glacial age, — might appropriately be 

 called The Eskimo Period. This name, derived fi-om a higher order 

 of beings than that which gave the name Beindeer Period., is much 

 more suggestive and is probabl}' of full3^ as wide application as 

 the latter name, A term already in use, the Palaeolithic Era, is 

 also convenient. 



It has been held that the occurrence of palaeoliths at Trenton 

 offered evidence of a very high antiquity of man in America, and, 

 the gravel being considered as a glacial moraine, that man's exist- 

 ence was carried back to interglacial and even pregiacial times. ' 

 As we have seen, the geological investigations along the Delaware 

 Yallej", described in this paper, throw quite a new light upon this 

 subject. They show that the implement-bearing gravel is of post- 

 glacial age, and is a river deposit of comparativeh^ recent forma- 

 tion ; and that neither in the gravels of the Champlain epoch nor in 

 de])Osits of any previous age have any traces of man been 

 discovered. The evidence appears to indicate the origin of 

 man at a time which, geologically considered at least, is recent. 



The actual age of the Trenton gravel, and the consequent date to 

 which the antiquity of man on the Delaware should be assigned, is 

 a question which geological data alone are insufficient to solve. 

 The only clue, and that a most unsatisfactory one, is afforded bv 

 calculations based upon the amount of erosion. This, like all geo- 

 logical considerations, is relative rather than absolute. The same 

 reasoning that showed that the modern river channel might have 

 lieen excavated in hundreds rather than 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, 

 lie is fully aware that any close approximation can safely be 

 arx'ived at only by extended comparison with other river gravels and 

 by a much more complete series of observations than have yet 

 been possible. Ethnological considerations, which make paljco- 

 lithic man to antedate the oldest races of the mound-builders, will 

 Jiave a bearing upon this question. Meteorologists ma^^ show that 



1 It will be remembered that Sir Charles Lyell, in his Principles of Geol- 

 ogy, 11th Ed., vol. 1, p. 286, conjectures the period of the gi'eat glacier to 

 have been about 200,000 years ago. 



