Review of Recent Geological Literature. 317 
•our Atlantic coastal plain, permitting the two series to be compared 
and correlated as to their age and conditions of origin. 
Professor Salisbury, coming with a large experience of exploration 
of the glacial drift in Wisconsin and other states of the upper Missis- 
sippi region, has worked on the Pleistocene problems of our Atlantic 
border, in the intervals of other duties, during twelve years. The pres- 
ent volume is his report on the glaciated northern third of New Jersey. 
It does not proceed, however, to the desired correlation of the glacial 
drift with the Lafayette and Columbia formations, well studied by 
McGee, Darton, and others, on the coastal belt of the southern states. 
This chief fruitage of the glacial work in New Jersey is reserved, to be 
given, as we may hope, in a later report, which should treat, with ample 
details, of the Pleistocene series in the southern part of this state. 
A general description and discussion of the drift and the Glacial 
period form Part I, in 226 pages. The conditions which lead to the 
accumulation of glaciers and ice-sheets, the manner in which they affect 
the surface of a region on which they lie, and the forms and disposition 
of their deposits, are analyzed in detail, with abundant references to the 
glacial deposits of New Jersey. 
The remaining and greater part of the volume deals very fully with 
local details, describing the terminal moraine, till, striae, kames, eskers, 
stratified plain and valley drift, loam, brick-clays, etc., mainly arranged 
under three divisions, the Appalachian region, the Highlands, and the 
Triassic plain. 
Referring to the cause of the glacial climate, Salisbury rejects the 
astronomic theory of Croll, which would give about 80.000 years as the 
measure of Post-glacial time. Instead, he thinks it to have been a com- 
paratively short period of 6,000 to 10,000 years, according to estimates 
by G. K. Giltert and N. H. Winchell, derived respectively from Ni- 
agara and the Falls of St. Anthony. 
The view that the Ice age was due to great elevation of the lands 
occupied by the glacial drift, as held by Dana, Upham, and Wright, is 
also rejected; and the submarine continuation of the Hudson river 
channel, to a depth of 2,800 feet beneath the sea level off the coast of 
New Jersey, is not mentioned, although it proves so great elevation 
of this part of our continent about the time of the ice accumulation. 
Preference is given to the hypothesis of Chamberlin, which attrib- 
utes glacial conditions to changes in the amount of carbonic acid gas 
contained in the atmosphere. It is thought that these changes, affecting 
the entire earth, and tending everywhere to contemporaneous increase 
or decrease of glaciation, that is, to cycles of glacial and interglacial 
stages on the borders of ice-sheets, are most harmonious with what is 
known concerning the North American and European glacial drift and 
the fluctuations of glaciers in mountain regions. 
Beyond the prominent terminal moraine in New Jersey, scantier 
and older glacial drift, referable perhaps to the Kansan stage of the 
Ice age, is found, in quite irregular and patchy distribution, to a max- 
