24 BIG SPRING PRAIRIE. 
ials of the glacial epoch were deposited in such a man- 
ner that a lake was formed on the present site of the 
prairie, a greater deposition of drift occurring at the 
south end of the valley, and also to the north and west 
of the prairie area. 
This lake differed but slightly in outline from the 
ptesent prairie, and it differed considerably in depth. 
From borings on this area the greatest depth did not 
much exceed thirty feet and considerable portions were 
only a few feet in depth, for in some localities the diff- 
erence in depth between the surface level and the drift 
clay or solid rock is quite slight. Bowlders resting on 
shallow drift clay occur in angle formed by the road- 
beds of the Hocking Valley R. R. and the Northern 
Ohio R. R. and just east of this point, in fact just 
across the tracks, the Niagara limestone lies scarcely 
two feet below the surface. Bowlders also occur on 
a rather large area in the vicinity of Springville. 
Further investigation would be needed to determine 
whether the preglacial stream flowed northward or 
southward between the North and West Ridges. 
That this area was a lake in post-glacial times is 
evidenced by the fact that quicksands, old lake beaches, 
sand-dunes, etc., exist in various portions. These will 
be more fully discussed under the various natural areas 
and plant societies into which the prairie can be divided. 
‘When this region was first settled, the natural drainage 
of the southern portion of the east arm was a broad 
gradual slope to Spring Run, joining it at the present site 
of the Gault House, Carey, Ohio. No definite stream 
existed in this portion within the memory of man; 
but that such an outlet formerly existed is evidenced 
by the fact, that the nearly obliterated remains of a 
beaver dam occurs in the southern portion of this 
area. It extended in an easterly and westerly dir- 
ection about half way between Dow street and the 
Northern Ohio R. R. It filled the gap between the 
