980 THE JOURNAL OF GEOLOGY. 
the state well to the eastern border of the coal field. In general geo- 
logical features they are essentially similar. The indurated rocks 
include the Augusta and Saint Louis limestones and the Des 
Moines Coal Measures. The first two are, for this district, con- 
formable. The erosion unconformity between the Saint Louis 
and the Des Moines is strikingly exemplified in Mahaska county at 
Corrier’s Mill and Raven Cliff, and in Keokuk county at What Cheer. 
The Saint Louis in its full section shows from the top downwards (a) 
Pella beds, fossiliferous marls and bedded limestones, (4) Verdi beds 
irregularly alternating limestones and sandstones; and (c) Springvale 
beds, blue shales and earthy magnesian limestones. ‘The Des Moines 
beds are made up largely of shales, with certain heavy sandstones and 
at least two coal horizons of which the lower is widespread and well 
opened up, and the upperis confined toasmall portion of the Muchakinock 
Valley. The two counties are important coal producers, their aggre- 
gate tonnage for the year 1893 being 1,363,880 tons. ‘The sandstones 
of the Coal Measures seem to mark local differences in sedimentation 
rather than a general horizon. ‘There is evidence of some erosion 
during Coal Measure time. A series of slight parallel anticlinals cross 
the county from northeast to southwest. 
The drift covers both counties in a sheet of very irregular thickness. 
It includes blue and _ yellow tills, local gravel and sand deposits, and 
an overlying silt or loess-like bed. The latter reaches no great 
thickness, but is an important source of material for clay-working 
industries, the total value of whose products for the year 1893 was 
$120,312. No distinct evidence of a well-marked forest bed is found 
and the correlation of the drift with that of other portions of the state 
is not attempted. Glacial striz being S. 42° E., and a later set bear- 
ing S. 70° E. (magnetic), are found near Eddyville. The reports are 
illustrated by figures, half tones, cross sections and maps. On the map 
of Keokuk county a small area in Section 7 of Liberty Township, 
which the text shows to be Coal Measures, is by mistake colored as Saint 
Louis. 
Geology of Montgomery County.—By E. H. Lonspatr. The 
exposed geological formations of Montgomery county represent 
three systems, the Pleistocene, the Cretaceous, and the Carbon- 
iferous. Alluvium, loess and till make up the Pleistocene, and the 
combined thickness of these three deposits amounts to nearly roo feet. 
The Cretaceous, which consists for the most part of friable grits, con- 
