Review of Recent Geological Literature. - 51 
Iowa Geological Survey , Vol. IV, Third Annual Report , 1894, with 
accompanying papers. Samuel Calvin, State Geologist. (467 pages, 
with 11 plates, 56 figures and 6 maps. Des Moines, 1895.) Aside from 
the administrative reports, which occupy 33 pages, the entire volume is 
devoted to county geology. Six counties are reported upon, and their 
stratigraphy, physiography and economic products are thoroughly de¬ 
scribed . 
The report on the “Geology of Allamakee County” is by Samuel 
Calvin. The area therein considered is in the northeastern corner of 
Iowa and is of special interest since it lies within the driftless area. 
Its topography is thus in sharp contrast with that of the surrounding 
drift-covered region, and on account of its strikingly irregular surface 
it has been called the “ Switzerland of Iowa.” The streams entering 
the Mississippi have cut steep sided valleys to a depth of 500 feet. The 
following formations occur within the county : Cambrian, represented 
by the St. Croix sandstone, and Ordivician, represented by the Oneota 
limestone, St. Peter sandstone and Trenton and Galena limestone. The 
only extensive lead mine ever discovered in the Oneota is located in 
Allamakee county, and here over 500,000 pounds of ore have been 
mined. The report concludes with an article on the “ Forest Trees of 
Allamakee County ” by Prof. T. H. McBride. 
In the “Geology of Linn County,” by W. H. Norton, the Silurian 
and Devonian rocks of this district, which lies in the east central part 
of the state, are considered at length and the character and relation¬ 
ship of the different beds are fully described. 
“ Geology of Van Buren County,” by C. H. Gordon. This county 
lies near the southeastern corner of the state. Its indurated rocks be¬ 
long entirely to the Carboniferous, and the Lower Coal Measures (Des 
Moines stage) cover the larger part of its area beneath the drift. Coal 
is mined at several places. 
“ Geology of Keokuk County ” and “ Geology of Mahaska County,” 
by H. Foster Bain. These counties are in the southeastern portion of 
the state. The formations represented are the Augusta and St. Louis 
of the Lower Carboniferous, the Des Moines stage of the Upper Car¬ 
boniferous, and the Pleistocene. The rocks underlying the greater 
portions of Keokuk county belong to the St. Louis stage, while those 
of Mahaska county were formed during the Des Moines stage. These 
two districts are important as coal producers. Keokuk county lies to¬ 
wards the eastern margin of the Iowa field and the Coal Measure 
strata are comparatively thin. The What Cheer district in this county 
is one of the more important in the state: in and about What Cheer 
fifty square miles are underlain by the Coal Measures. Mahaska county 
has long been the most productive coal district in Iowa. Thirty mines 
are in operation at present and about half of this number are shipping 
mines with an output of from 200 to 1000 tons per day, while the 
annual output for the county is over one million tons. 
“Geology of Montgomery County,” by E. H. Lonsdale. The 
stratified rocks of this county, which is located in the southwestern 
