32 BIG SPRING PRAIRIE. 
most of the earlier ditches were dug» chiefly along the 
edges of prairie, thus intercepting the waters from the 
springs. ‘The destruction of the forests on the ridges, 
and the construction of tile ditches and open ditches 
have considerably lessened the importance and magni- 
tude of the springs along the margin of prairie, thus 
aiding in the evolution of plant societies. After the 
soil became drier, and especially after the construction 
of the Hocking Valley R. R. across this area, prairie 
fires became prevalent. 
In order to investigate the amount and causes of 
the settling of the soil, direct experiments with soils 
were performed. Samples of soil were collected, 
weighed, and measured while still wet. After thorough- 
ly drying in a slow oven, the soil was again weighed 
and measured. ‘The dry soil was then burned, and the 
weight and volume of ash determined, in order to learn 
what amount of settling of soil was due to prairie fires 
and what amount todrainage. These prairie fires have 
rapidly changed a mesophytic area to a hydrophytic 
one, extensive depressions occurring on the areas burned 
over, and as the drainage of the ditches became more 
sluggish, these depressions would fill with water, which 
would scarcely dry up even in dry seasons. A number 
of such areas came under the writer’s observation be- 
tween 1891 to 1897. In the latter year the outlet was 
deepened by blasting the rock in bottom of ditch from 
the point where the outlet empties into Spring Run to 
the bridge just north of the Northern Ohio railroad sta- 
tion. ‘The point where deepening ended is shown in 
figure 4, the rude fence marking the limit. 
