416 Geology of Johnson County. 
“No. 5. Ancient soil, two feet thick, very dark loam, resembling 
the peat, but more decomposed. Contains no shells or other fossil 
remains. 
“No. 6. Blue clay, very tenacious, containing sand, gravel, and 
small boulders; pebbles and boulders, all water-worn, and many of 
them distinctly glacier scratched. Thickness unknown. 
“ The exposure was made by the excavation of the Chicago, Rock 
Island and Pacific Railroad Company, previous to which there was 
no appearance at the surface to indicate the presence of anything 
more than the ordinary drift deposit.” 
Bed No. 5 of this series is undoubtedly only a more thoroughly 
decomposed and finely comminuted portion of bed No. 4. This 
bed of peat, also, like that at Iowa City, contains remains of 
Coleopterous insects. 
While boring a well on the northeast quarter of section ten, 
township eighteen, range five, in Linn County, a deposit of peat 
and coniferous wood four feet.in thickness was struck at a depth of 
ninety-nine feet below the surface. From this well, into which a 
tight galvanized iron tubing has been forced, escapes a constant 
supply of natural, combustible gas (the peat probably being the 
origin of it), but whether of sufficient quantity to be of practical 
value, is a question to be answered by investigation. A few miles 
from this locality another well of the same character is reported. 
In the northern portion of the State the peat formation is seldom, 
f ever, observed as a member of the forest bed. These beds of 
peat are of interglacial origin, and was coexistent with the 
luxuriant forests of conifers which, in interglacial times, covered 
the surface of what is now known as Jowa.! The occurrence 
also of the well-preserved seeds of plants and the abund- 
ant remains of insects in this formation are features of pecu- 
liar interest. 
A critical and somewhat extended study of the forest bed and 
other superficial formations in different portions of the State, 
reveals facts which seem to substantiate the theory advanced in 
regard to the relative age of the peat formations. ` 
The topography of the surface of Johnson County is, for the 
most part, peculiarly that of loess regions, being more or tess 
broken and rolling, the elevations having rounded tops, and more or 
1'These beds of peat were believed by Dr. White not to be of interglacial 
origin. White’s Geological Survey of Iowa, vol. i., p. 121. 
