Remeio of Recent Geological Literature. 415 
Brunswick, the St. Lawrence valley, and the lake Champlain basin, may 
be parts of a single subsidence from which the southern area was up- 
lifted earlier than the northern. 
If the Ice age was primarily caused, as Jamieson, Upham, Wright, 
Hilgard and others maintain.bygreatepeirogenic uplifts of the glaciated 
portions of the continents some thousands of feet higher than now, then 
the gradual though fluctuating recession and departure of the ice-sheets 
were probably conversely due to the depression of the ice-loaded lands 
to their present hight or lower. When the depression had caused a con- 
siderable glacial retreat, the increase in thickness of the ice-sheets by 
series of centuries bringing exceptional snowfall may have raised their 
surface so high that now and again the ice was enabled to advance far 
over tracts which it had previously abandoned, leaving its conspicuous 
moraines as marks of these stages of fluctuation. After the borders of 
the drift-bearing area were unburdened by the glacial recession, they 
appear soon to have been moderately uplifted, attaining their present 
hight or oscillating somewhat above and below this hight. A chiefly 
permanent wave of elevation, slowly extending from south to north as 
the ice-sheet fluctuatingly departed, seems to have raised earliest the 
silt and loess area of the Ohio, Mississippi, and Missouri region, later 
and progressively the areas of the glacial lakes Agassiz, Warren, and 
Iroquois, with the Champlain and St. Lawrence valleys, and latest the 
region of Hudson bay, where, according to Dr. Robert Bell, this uplift 
is still in progress and now averages apparently several feet in a hun- 
dred years. The Postglacial or Recent period has been too short both 
in North America and Europe to bring yet the full restoration of isostasy 
by completion of the uplift of the glacially depressed portions of these 
continents, for as about Hudson bay so in Scandinavia the postglacial 
elevation still continues at a measurable rate. 
The Moon's Face; a study of the orirjin of its features. By G. K. Gil- 
bert. Address as retiring president, delivered Dec. 10, 1892. Bulletin, 
Phil. Soc. of Washington, vol. xii, pp. 341-293, with a plate and four- 
teen figures in the text. The geologist here becomes a selenologist. 
Whoever has looked with a telescope, even of the small power of the 
ordinary surveyor's level or transit, upon the illumined face of the 
moon and seen its so-called craters, especially when at the moon's 
quarter phases their serrated rims cast long shadows near the boundary 
of the lighted area, must have wondered at the apparent violence and 
grandeur of the volcanic action to which these scars of our satellite 
have been commonly ascribed. Mr. Gilbert, however, shows in this 
paper that the lunar craters differ so much in their range of magnitude, 
in the deep depression of their central plains below the outer expanse 
surrounding the crater rims, and in other respects, from terrestrial 
craters, whether of the Vesuvian or Hawaiian types, that they cannot 
reasonably be supposed to be of volcanic origin. He thinks, therefore, 
and sustains his view with very able arguments, that the moon has come 
to its present form from the breaking np of an original ring of satellite 
matter, like the rings of Saturn. Many agglomerations of this matter 
