418 Geology of Johnson County. 
very gradual and imperceptible gradations. In a railroad cut, 
about one and one-fourth miles west of Iowa City, the loess is seen 
to attain a thickness of twenty-three feet and five inches. 
The humus-stained division, No. 1, attains a thickness of five 
inches; while the second, or yellow division, attains a thickness of 
about twelve feet; and below this, the third, or blue division, which 
attains a thickness of eleven feet, and rests immediately upon the 
drift. This portion contains an abundance of fossils, most of which, 
however, are in a better preserved condition than those of its 
equivalent at the “ brick-yard.” 
One mile south of Iowa City the loess is seen to attain a thick- 
ness of twenty feet, and is very fine and homogeneous throughout, 
being of a yellow or yellowish-buff color, with the exception of a 
humus-stained layer, of a few inches in thickness at the top. The 
yellow clay at this locality rests directly upon the drift, the blue 
division being absent, as also fossil remains, so far as observed. 
At Oxford, in the extreme western portion of the county, the 
typical yellow loess is seen to have a thickness of from fifteen feet 
to twenty-two feet, the blue division, however, not being present. 
No fossils were observed in the loess in this region. Occupying 
the same relative position to the loess, and presenting the same 
general character as at other described localities, is the drift forma- 
tion. At this locality, as well as several others in the county, the 
loess is seen to contain more or less extensive accumulations of fine 
silicious sand ; also, at two or three places, I observed small accu- 
mulations, or pockets, of well-rounded and smoothed quartz and 
greenstone pebbles of drift origin. This material may have been 
derived from detritus ladened ice, floating from the north and 
dropping its burden while this formation was in process of deposi- 
tion. At numerous localities the loess contains abundant calcareous 
concretions and ferruginous tubules of various dimensions, while 
at other localities it is devoid of them. 
At Solon, in the northeast part of the county, the loess is some- 
what thinner than at the previously-described localities, but i 
essentially the same, although the lower, blue, division is not 
noticed, and the upper, black, humus-stained layer, is somewhat 
thicker, owing to the somewhat less broken surface, and the lessened 
facility with which the surface is “ washed ” by rains, thus remov- 
ing much of the humus accumulated by decomposing vegetation. 
