416 
GLACIAL GEOLOGY 
San Francisco group of volcanoes in northern Arizona, where, 
more than 400 vents of all sizes and many dates occupy a circum¬ 
scribed area. Volcanoes of the Pacific Coast are all almost out of 
question. 
Although this appears to be the first announcement of an oc¬ 
currence of volcanic ash in Iowa it is perhaps not nearly so 
unusual a phenomenon as might be inferred. Now that the exact 
stratigraphic hoiizon is determined numerous other deposits may 
be expected to be speedily found. Because of the fact that the ash- 
beds of the kind under consideration are eolian deposits, their 
positions are uneflected by the ordinary means of deposition. 
Then, too, the determination of the exact age enables certain 
similar beds in Nebraska, as noted by Todd, to be placed and cor¬ 
related. With the western extension of these correlations we 
may confidently expect at no distant day the tracing of the Iowa 
deposits to their exact vent of eruption. 
The volcanic ash as seen under the microscope appears as sharp, 
angular fragments of clear, amorphous glass, wholly without 
trace of crystal structure. This dust is quite characteristic of the 
pumaceous glasses usually found in ash-cones built around vol¬ 
canic vents. 
Keyes 
Original of McGee's Complex Drift Sections. The patent efforts 
of the members of the Iowa Geological Survey to discredit the 
fundamental observations of their predecessors in the State can 
rebound to no lasting personal preferment. This pernicious 
policy is nowhere better emphasized than in an implied rectifica¬ 
tion of W. J. 'McGee’s now classic sections of the Pleistocene 
deposits on Capitol Hill, in Des Moines, as recently set forth 
by J. H. Lees,^ assistant state geologist, whose office overlooks 
the prospect. Attention would not be called to the matter, un¬ 
ethical as it is, were it not to correct gross, albeit unwitting, 
mistatements of fact, and resulting inference unwarranted — 
assertions already allowed to go too 'long unchallenged. McGee 
and Call and Calvin are no longer with us to defend their theses; 
and others best informed concerning the original contentions are 
1 Proc. Iowa Acad. Sci., Vol. XXIII, p. 167, 1917. 
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