Editorial Comment. 53 
number of the Quarterly Journal of the Geological Society, 
Prof. Joseph Prestwich concludes that "the epoch of extreme 
cold may come within the limits of 15,000 to 25,000 years, and 
the Post-Glacial S,ooo to 10,000 years. This might give to 
palaeolithic man, supposing him to be of so-called pre-glacial age, 
no greater antiquity than perhaps about from 20,000 to 30,000 
years; while should he be restricted to the so-called post-glacial 
period, his antiquity need not go further back than from 10,000 
to 15,000 years before the time of neolithic man." 
Prestwich bases this conclusion partly upon the new data of 
glacial movement. It is found that while the Alpine glaciers 
flow about 300 to 400 feet annually, those of Greenland flow 
at the amazing velocity of 6,000 to 16,000 feet annually, i. e.,. 
about forty times as fast. The conditions in Greenland are far 
nearer those of the Glacial period than are those in the Alps. 
The result is to reduce the period of glaciation, since the work 
was done so much more rapidly than was previously supposed. 
In like manner the more accurate investigation of the gorge of 
Niagara has reduced the time of its erosion to 6000 or 7000 
years. The whole drift of opinion is decidely towards a very 
moderate estimate of Quaternary time. 
Shall we see the same result in respect to the Tertiary P In 
the Nineteenth Century for November 1SS7 Mr. Alfred R. 
Wallace reviews the American evidence of human antiquity) 
dwelling especially upon the California finds which associate 
man with the Pliocene period. He deplores the skepticism 
which has hitherto excluded this evidence. But it is better to be 
over- skeptical than over-credulous. The reluctance to admit 
the proofs of Pliocene man has led to the same sharp scrutiny 
of the age of the auriferous gravels which has been so beneficial 
in the cases mentioned above. May not the Pacific slope 
have run so different a course of development that the so called 
Pliocene there overlaps the Quaternary of the Atlantic slope? 
Already we have the opinion of Dr. Alexander Winchell, in 
the March number of this journal, that the great western out- 
flows of lava occurred in the Glacial period, and of Gilbert and 
McGee of the U. S., Geological Survey that the Equus 
fauna should also be co-ordinated with the same period. 
The general result of the controversy about the antiquity of 
