MADISON COUNTY. 
The surface of the county, however, has been preatly relieved by drains 
and ditches, and is susceptible of almost indefinite improvement by such 
agencies. | 
None of the streams have deep valleys, but the surface lies in gentle 
undulations between the channels of contiguous water-courses. In the 
north-eastern corner of the county, the low summit that divides the 
waters of Little Darby from that of Big Darby, extends in the broad and 
productive tract know as the Darby Plains, one of the most famous graz- 
ing districts of the State. 
GEOLOGICAL SERIES. 
The geological scale of the county is very much contracted. But twe 
formations besides the Drift occur here, viz., the Helderberg and the 
Corniferous limestones. There are in the county two exposures of the 
former and but a single one of the latter. 
The Helderberg limestone (water-lime) has been quarried in small 
amounts for many years on the tarm of Asa Hunt, Pike township, (sur- 
wey 6,965). A branch of the Spring Fork of Little Darby know as Bar- 
ren Run, has cut its bed down to the limestone for a number of rods and 
the stone is raised from the quarry at such times as the water is lowest. 
it has been used for time and also for building stone. The first purpose 
it is very well adapted to; the second, it answers but indifferently well, as 
the stone is thin and sheliy. It holds its characteristic fossils which, 
‘however, are not necessary for its identification—as the lithological chaxac- 
ters are too plain to be mistaken. 
The second exposure of this limestone is much more considerable. It 
occurs on the Stoner farm in Jefferson township, two miles seuth of the 
village of West Jefferson. A section of 15 feet of this formation is shown 
in the banks ef Little Darby, very near the point where the stream leaves 
the county. The ledge is resorted to for the same purposes as the ex- 
posures first mentioned, viz., for lime and building stone. The same 
remarks as to quality will apply in this case as before. The lime has an 
excellent reputation, being much milder than the Columbus lime. 
The principal interest of this locality, however, lies in the fact that it 
furnishes the junction of the Silurian and Devonian formations. A few 
rods from the exposure of the Helderberg limestone just mentioned, ten 
feet of another formation come in which it is easy to identify by all 
tests as the Corniferous limestone, known in this portion of the State as 
the Columbus or State quarry limestone. The beds furnish quite service- 
able building stone, and are brought into neighborhood use. 
