W. Upham— Estimates of Geologic Time. 219 



approximately its present height, with only moderate uplifts 

 and depressions. Drawing his ratios of Postglacial and Glacial 

 time, and of the preceding early Quaternary or late Tertiary 

 epoch to which the Lafayette formation belongs, from the 

 amounts of stream erosion, he has supposed the conditions 

 then similar to those of the present time, so that the relative 

 durations of these epochs may be estimated from their excava- 

 tions of valleys by water courses. But it seems preferable, as 

 before noted, to refer the Ice age to great elevation of the 

 land, whereby the erosion of streams would be caused to pro- 

 ceed very much more rapidly than if the country were as low 

 as now. With an altitude of our Atlantic coastal plain and 

 whole continental area westward 3,000 feet higher than now, 

 the valley-cutting may have gone forward twenty or a hun- 

 dred times faster than to-day, or even near the coast a thousand 

 times faster than now. The factor with which Mr. McGee 

 starts on the multiplication of the earlier ratios to change 

 them to years is evidently far too large, and it gives therefore 

 for all the geologic eras and for the earth's total age too vast 

 figures probably by twentyfold to a hundredfold. 



Anthropologists, not less than geologists, have a lively 

 interes' .in the estimates and measurements of the length of 

 the Glacial and Recent periods, for the earliest reliable testi- 

 mony of man's existence comes to us from the Ice age, both 

 in North America and Europe. Confining our attention to 

 the observations which prove that men w^ere living on our 

 continent as contemporaries of its northern ice-sheet, we have 

 many independent and widely separated localities where traces 

 of man's presence during the Glacial period have been found. 

 Under the beach ridge of gravel and sand on the south side of 

 Lake Iroquois, the glacial representative of Lake Ontario, 

 charred sticks, with ashes and stones laid to form a rude 

 hearth, were discovered about 18 feet below the surface in 

 digging a well in Gaines township, Orleans county, 1ST. Y. 

 Lake Iroquois was dammed on the northeast by the receding 

 continental ice-sheet and outflowed by way of the Mohawk 

 and Hudson. The hearth and fire were made, according to 

 Mr. G. K. Gilbert, "not long after the establishment of the 

 Mohawk outlet and during its continuance." To a much 

 earlier stage of the glacial recession we must refer the exten- 

 sive gravel deposits of the Delaware River in the vicinity of 

 Trenton, 1ST. J., in which Dr. C. C. Abbott, Prof. F. W. 

 Putnam, and others have found many palaeolithic implements 

 and chipped fragments of argillite.* Somewhat farther south, 



* Since this paper was written, two articles by Mr. W. H. Holmes in Science 

 (Nov. 25, 1892, and Jan. 20. 1893) lead me to uncertainty whether the traces of 

 man's existence in this country during the Glacial period are referable, as has 

 been hitherto supposed, to a technically palaeolithic stage of culture. They seem 



Am. Jour. Sci. — Third Series, Vol XLV, No. 267. — March, 1893. 

 16 



