Conglomerates in the Galena Series. — Sardeson. 
j*:^ 
It would not be just to infer that in consequence of these 
objections the "elevation-theory," as it may be called, is not 
a valuable contribution to glacial literature. On the contrary 
every possible solution of even a part of the greatest problem 
in Pleistocene geology is welcome. Even if it prove incapable 
of solving the whole it may yet be an important aid to the at- 
tainment of the desired results. Probably the publication of 
Dr. Croll's hypothesis even if it should prove, as now seems 
likely, entirely incompetent, has done more to stimulate the 
progress of glacial geology than any other single event of this 
century. 
It is scarcely necessary to add that any theory of the Ice 
age must be capable of explaining all the many and intricate 
facts connected with it and must, of course, be in accord with 
the actual course of recent geological history. At the same 
time the full investigation of all the physico-geological ramifi- 
cations of any fundamental first cause of the Ice age must be 
a task of excessive intricacy and length. Consequences may 
come to light apparently quite unrelated to it which are yet 
its necessary though distant results, and it is not improbable 
that this strange chapter in the history of the earth may at 
last be found to be an outcome of more than one principal 
cause whose interaction has brought about the remarkable 
consequence — a singular point in a curve — an intersection of 
two mathematical lines — a physical result exalted by acci- 
dental coincidence w'ith another. 
INTRAFORMATIONAL CONGLOMERATES IN THE 
GALENA SERIES. 
By F. W. Sardeson, University of Minnesota. 
(Plate IX.1 
The continuation of the Trenton and Hudson River 
groups, as they are most often designated, from New York 
state westward through and beyond the Ohio river basin, is 
well known to geologists and a description here of their extent 
