Geology of Johnson County. 415 
stiff, distinctly stratified blue clay. This formation has been struck 
at numerous localities at a depth of from twenty-eight feet to sixty 
feet below the surface, in the central portion of this county. A usual 
feature of the peat division of the forest bed of this region are the 
remains of Coleopterous insects. The peat at all these localities was 
evidently formed where it is now found, and are parts of one and 
the same bed. 
A limited deposit of similar ancient peat was also discovered in 
Adair County, one hundred and seventy miles to the westward of 
Iowa City, on section twenty-two, township seventy-five, range 
thirty-two. This bed was found to be between two and three feet 
in thickness. The drift, apparently only slightly if at all modified, 
rested directly upon it, and it was underlayed by a dull, bluish- 
clayey bed. 
At another locality, near Davenport, fifty miles east of Iowa 
City, a deposit of peat occurs almost upon the very brow of the 
bluffs that border the valley of the Mississippi. This example 
is one of unusual interest, in consequence of the existence there of 
an extensive bed of ancient peat which is covered to th depth of 
several feet beneath the prairie soil, and the discovery in the clay, - 
above the peat, of the remains of a mammoth. 
The following section, compiled from White’s Geological Survey 
of Iowa, vol I., part i., pp. 119, 120, will show the position of the 
deposit in relation to the drift :— 
“No.1, The ordinary prairie soil, one foot. The prairie here 
extends to the edge of the bluff, gently sloping backward toward 
the north. 
“ No. 2. The ‘yellow elay’ or loam, twenty feet thick, iron- 
stained, frequently distinctly laminated; lamine curved, and have 
their layers of sand interstratified in some places. It contains 
small calcareous nodules and shells of the genera Succinea, Helicina 
and Pupa. 
“No, 3. Bluish-grey clay, three to five feet thick, not stratified ; 
contains a few shells like those of No. 2. A tusk, several teeth, 
and some other portions of Elephas primigenius (?) were found, 
Just at the junction of Nos. 2 and 3. : 
“ No. 4. A bed of brown peat one foot thick, which burns toler- 
ably well. In some places the peat moss, Hypum aduncum, was so 
well preserved as to be recognized. Quantities of re citecks aac uae 
coniferous wood are distributed throughout this bed. 
