White on later Cretaceeus deposits i^i loiva. 221 
philosophic mind of Gray was strongly attracted by the breadth and 
scope of the views of Darwin, and came rapidly under the spell of their 
influence. To him Darwin was indebted for many facts both in favor of 
and in opposition to his theory of natural selection. Both were equally 
welcome. The attachment of the two men was mutual. In one of his 
early letters Darwin writes: "You are more than anyone else the 
thorough master of the subject. You know my book as well as I do 
myself and you bring to the question new lines of illustration and argu- 
ment in a manner which excites my astonishment and also my envy. 
Every word seems weighed carefully and tells like a 32-lb. shot." It fell 
to the lot of Asa Gray to fight the battle of evolution in America almost 
single-handed against the immense influence of Agassiz, who while op- 
posing the doctrine to the last contributed by his embryological studies 
some of the most powerful arguments in its support. Dr. Gray entered 
the field alone but from the first he gave no uncertain sound. Though 
he never went to the full length with his friend, always maintaining that 
the stream of variation had been, as he phrased it, " beneficially directeJl," 
yet in 1S60, or the year after the appearance of the "Origin," he wrote 
three articles in the Atlantic Monthly which now form the third chapter 
in his " Darwiniana," under the heading, " Natural Selection not incon- 
sistent with Natural Theology." With this limitation Dr. Gray continued 
among the foremost and most consistent advocates of Natural Selection 
in this country to the time of his recent death ■} but as his application of 
the doctrine was almost entirely to the science of botany to dwell longer 
on it here would scarcely be in place. 
ON THE OCCURRENCE OF LATER CRETACEOUS 
DEPOSITS IN IOWA. 
BY CHARLES A. WHITE. 
The existence of Cretaceous strata in ^vestern Iowa has long 
been known ; and they have been discussed and referred to by 
various authors. Those which are exposed in the neighbor- 
hood of Sioux City were first recognized as of Cretaceous age 
by Owen;^ and for several years thereafter no other exposures 
were known to exist within that state. In the course of my 
official work upon the geology of Iowa other exposures of 
Cretaceous strata in situ were discovered at localities farther 
eastward from the Missouri river. The more southerly of 
these exposures, as well as a part of those in tjie vicinity of 
. ' January 30th, 1S88. 
2 .See maps of Geol. Survey of Wiscoubin, Iowa and Minnesota. 
