IOWA ACADEMY OF SCIENCES. 
57 
bottom of an irregular, basin-like depression. Taking this 
into account, and the difference in the occurrence of the wood 
of the two strata and their definite line of separation, one won- 
ders whether the relation of the lenticular layer of clay may 
not be closer to the yellow clay above than to the blue below. 
The gradual blending of the upper into the middle stratum has 
been noticed, and the fact that wood occurs even in the trausi- 
tion between the two beds leads one to question whether it 
might not have been found up through the yellow clay were 
not that bed so loose of texture. 
Next below the four feet of blue clay occurs a peaty bed that 
shows the same saucer- shaped depression as the clay above. 
On its upper surface, separating it from the clay, is a sheet of 
incoherent white sand which is fairly pure and shows irregular 
lines of sedimentation. Its thickness varies from nothing to 
six inches but it is fairly constant over most of the surface of 
the peat. The peaty formation has at the center a thickness of 
four feet, but it thins out and disappears within 300 feet in 
either direction. Its brown color makes it the best defined bed 
of the exposure, yet it is in structure far from uuiform. The 
planes of stratification are frequently irregular, rising through 
the bed to the eastward. Such parts are clearly the results of 
sedimentation. Other layers are pure peat in regular and 
extensive sheets composed of closely compressed laminse of 
moss as plain as if it was fresh from the botanist’s press. These 
are certainly in situ. 
Other vegetal remains than moss are wanting. Repeated 
and careful search discovered but one fragment of wood which 
was found in a sandy loam that underlies a small part of the 
peat. No roots are found except small ones, apparently those 
of the moss. Below the peat is a greenish colored clay, the 
lowest formation found. At the middle of the section it is 
invisible because below the bed of the cut, 300 feet either way 
it rises to a height of six or eight feet. It is a compact clay 
containing a considerable amount of sand and quartz, and other 
crystalline pebbles, but no limestone fragments, neither does 
this formation, nor the peat, show any impregnation with lime. 
In the depression in this green glacial clay must have existed 
the swamp where the peat bogs formed during a great pause 
in the Ice Age. Upon this peat marsh came a fiood of clay and 
sand bearing in its embrace the forest debris and limestone 
fragments. Next came a huge windrow of drift building a hill 
