28 BIG SPRING PRAIRIE. 
an extent, that the mesophytic condition was gradually 
reverting to the hydrophytic condition again. 
As evidence of the settling of the soil and the ex- 
tent of the settling, we would call your attention to 
figure 1 which shows a large bowlder resting on drift 
clay. The location of this bowlder is indicated on the 
Map. ‘The dark band along the side of rock near the 
top marks the old marsh level; the shorter band of dark 
and light streak near the base of rock was exposed by 
prairie fire which burned the soil several years ago. 
The picture does not do justice to the real appearance 
of the rock. The portion above the upper band is old 
and exceedingly weatherworn, and partially covered 
with mosses. The portion below the upper band has a 
clean, bright surface as ifit had been more or less acted 
upon by humic acids. The difference in the appear- 
ance of these distinct areas is far more striking on the 
' bowlder than in the picture. The decrease in level of 
this part of prairie is thus shown to be about 22 feet. 
Mr. Peter Brayton states that when a young man, 
he was one day walking across prairie not far from the 
edge, ashort distance north of New Road 2, which 
crosses his farm. The ground was wet and springy. 
At each step, his feet would sink into the muck. He 
happened to step upon something solid. Upon inves- 
tigation, he found it to be a bowlder, whose top was 
slightly below the surface. In 1899, the bowlder was 
projecting about 20 inches above the surrounding level. 
This seeming elevation of bowlder, and actual settling 
of soil occurred after artificial drainage was introduced. 
The old settlers are quite unanimous in their testi- 
mony, that a person could shake many square rods of 
ground by jumping upon one of the “bogs” as they 
called the “sedgy hummocks”’ projecting above the 
general level; and also, that portions of prairie muck 
seemed to be quite deep as poles could be thrust vertic- 
ally into the soil to the depth of ten feet or more. At 
