Glacial History of Neiv England Islands. — Upham. 89 
thought by Shaler to be remnants of erosion, I ascribe to bar- 
riers of unmelted tracts of ice, towering high above the sand 
ridges and plateaus at their time of formation, but leaving them 
surrounded by low areas when the ice-sheet was fully melted. 
Therefore no geologically vast lapse of time is required, ac- 
cording to my view, for the post-Tertiary history. Probably 
a hundred thousand years for all the period of land uplift, gla- 
ciation, subsidence, departure of the ice, and subsequent dura- 
tion to the present day, would be nearer the truth. At least, 
such would be my estimate from a survey of the early Quater- 
nary and Glacial records thus far known on this continent ; and 
a nearly similar conclusion seems to be reasonably drawn from 
the Quaternary history of Europe. 
The well known physical researches of Lord Kelvin, Clar- 
ence King, and others, concerning the age of the earth as an 
abode of life, and the geological estimates and computations of 
Dana, Walcott, Reade, and others, indicate that no more than 
a hundred million years, or perhaps only thirty million years, 
more or less, have sufficed for all the life history of our globe. 
With this measure we find no decided disagreement, if the 
Quaternary era has occupied only about a tenth part of a mil- 
lion years; but a much larger estimate for this era would imply, 
by application of reliable ratios for the preceding geologic eras, 
a far longer duration of the earth. There is a solidarity of all 
truth, and when a part becomes discordant through inferences 
from unproved theories, it may be taken as a suggestion that 
the theories are probably erroneous and need revision. 
Bibliographic References. 
Without attempting to give a complete list of all papers 
bearing on the Quaternary geology of this peninsular and is- 
land district, it will yet be serviceable, for further investigation 
of the questions here considered, to cite as follows, in alpha- 
betic order of authors and chronologic sequence of their writ- 
ings, a large part of this literature, which mainly receives in 
Prof. Shaler's several papers very scanty discussion or mention. 
Chamberlin, T. C. Preliminary Paper on the Terminal Moraine 
of the Second Glacial Epoch. U. S. Geol. Survey, Third An. Rep., 
1881-82, pp. 377-381, relating to the terminal moraines of this district. 
Crosby. W. O. On the occurrence of Fossiliferous Boulders in the 
Drift of Truro, on Cape Cod, Mass., Proc. Boston Soc. Nat. Hist.. 
