452 GEOLOGY OF OHIO. 
of the country may have changed so that the land is readily-drained at 
present, and this still be the true explanation of these black lands in 
this and adjoining counties. Moisture made rank and abundant vege- 
tation, while it also impeded its entire decay. The partially decayed 
vegetable products accumulated, and mingling with the clay below, 
formed that rich, dark-brown loam. But there is unfortunately a larger 
area of thin and light-colored soil in the county than of the soil just 
described. This thin soil is not peculiar to this county, but is found in 
other counties situated in like manner. Its color shows it to be quite 
destitute of the products of vegetation. It differs equally from the yel- 
low clay soils of the uplands of Butler, Warren, and Hamilton counties, 
and seems less capable of being made productive. The clay of this 
class of soils is impermeable to water, and is so situated that water has 
drained off readily, and has not stood upon it in natural swamps. The 
soil is composed of a fine-grained material and is compact, and sheds 
water like a roof. How the circumstances in which the fine-grained ma- 
terial was deposited differed from those in which other drift deposits were 
made, I will not undertake to state.’ This soil seems to have been ex- 
hausted rather than enriched by ages of primeval vegetation. What 
chemical analysis would show it to lack of fertilizing material, I cannot 
say, but the deficiency of limestone pebbles in it would indicate that it 
might be lacking in lime, and it has not had the advantage of being 
overspréad with decaying bowlders, which add to a soil potash and other 
fertilizing ingredients. It seems to have been the least fine sediment 
deposited from receding water—lifeless water. 
This soil, lying so as to drain away water, and not of a nature to ab- 
sorb and retain it, became covered slowly with vegetation. But it al- 
ways lacked that rankness and exuberance of vegetation which lower 
and moister places possessed. Still many, countless, generations of plants 
and unknown crops of trees have grown and decayed here without leav- 
ing behind them much vegetable matter commingled with the soil. 
What has become of the substance of plants that it has not accumulated in 
the soil? The answer must be that the growth upon this soil have passed 
back to their original elements—have gone as they came—in the form of 
water and gases. The bulk of vegetation is composed of water (oxygen 
and hydrogen), carbonic acid (carbon and oxygen), and nitrogen. When 
vegetation decays these materials are evolved, and pass off into the at- 
mosphere. It is when decay is impeded that vegetable matter accumu- 
lates in the soil. Mould is partially decayed vegetation. When vegeta- 
ble products are protected from the atmosphere by water their decay is 
retarded and impeded, and certain compounds are formed of a complex 
