BIG SPRING PRAIRIE. ih 
from the evaporation of the water, which overflowed 
the surface of soil in vicinity of Ox Spring, and in part 
to the shells of fresh water mollusks inhabiting same. 
The water from this spring, and in fact from all 
wells in vicinity of ridges is heavily charged with lime. 
This marly soil effervesces briskly when treated with 
hydrochloric acid. The surface muck to the east of 
this section is of a deep black color, but at the depth 
of 3 or 4 feet it is of a brown color, resembling in this re- 
spect peat from aSphagnum swamp. A microscopic ex- 
amination of this brown soil reveals the fact that over 
nineteen-twentieths of it is composed of purely vege- 
table matter, the cellular structure being well pre- 
served. This lower stratum has the appearance, and 
slightly also the odor of well-rotted cow-manure. This 
brown muck when first exposed possesses a slight am- 
monia odor, which it soon loses. One form of plant 
remains consists of a wavy stem with 34 inch inter- 
nodes. The interior is well-rotted; the bark forms a 
brownish layer, which, after drying, crumbles under the 
least touch. It is this brown water-charged muck 
which gives that extreme spongy character to the soil. 
It would be interesting, if it were possible to determine 
whether this brown muck were due to the remains of 
Philotria, Ceratophyllum, Utricularia, Myriophyllum, 
ete , or to Typha, Juncus, Phragmites, Carex, etc. 
As before mentioned this vicinity possesses the 
deepest muck. Fig. 11 represents this natural meadow 
as viewed northward from the divide. The ditch 
represented is about 5 feet deep, and flows northward. 
By a close inspection of the illusrtation, the surface 
along each side of the ditch is seen to slope toward it; 
this slope is due to the settling of soil incident to drain- 
age and aeration. Between this ditch and the western 
margin of prairie, especially in the vicinity of the 
springs there occurs a plant society of the Heath type, 
three of whose species are quite characteristic of peat 
