Topography of Hon'ard Co., la. — Calvin. 38J. 
valley of the Iowa river, there is a bed of old, rotted, ferru- 
ginous Buchanan gravel about thirty feet above the present 
water level. Down in the valley — the difference in hight be- 
ing a measure of the erosion which took place in the interval — 
there are extensive terraces of perfectly fresh sands which 
were deposited when the lowan ice was melting a few miles 
farther up the stream. Whether comparisons be made on the 
leaching and segregation of the limy constituent of the two 
drifts, on the ferrugination and oxidation of the surface, on 
the rotting or decay of the surface bowlders, or whatever the 
test employed may be, the changes wrought by time in the 
lowan are too near to zero for satisfactory numerical expres- 
sion ; the changes in the Kansan are astonishingly great. If it 
should be claimed that the Kansan is a hundred times as old 
as the lowan, I know of no facts at present that would dis- 
prove the claim. If some one should estimate the age of the 
Kansan as fifty times as great as that of the lowan, I should 
be compelled to acknowledge that the estimate is very conserv- 
ative. 
Description of Plate XXVIl. 
Figure i. View in the Loess-Kansan area, aortheastern part of How- 
ard county, Iowa, showing the type of topography developed by pre- 
loessial erosion of the ancient Kansan drift. 
Figure 2. The loess margin or loess moraine at the border of the 
lowan drift in section 26, Albion township, Howard county, Iowa. 
The level space in the foreground is a part oi the lowan plain. 
Figure 3. A typical portion of the lowan plain in section 7, Oak Dale 
township, Howard county, Iowa. 
GEEST. 
By W.J. McGke, Washington, D. C. 
[From the Eleventh Annual Report, U. S. G. S., Part 1, pp. 277-280, 1889-90.] 
Despite its extent and its accessibility, the superficial man- 
tle of rock debris has received comparatively little attention ; 
it was too common to inspire the enthusiasm of research in the 
local student, and like the drift, of a generation past, was by 
many regarded only as an annoying obstacle to investigation 
of the underlying rocks. Yet within recent years many Amer- 
ican chemists and geologists have found it a worthy subject 
of studv. Hunt has well elucidated the conditions of its or- 
