THE SOILS OF FLORIDA. 
35 
plateau in the formation of occasional sinks of which the “Devil's 
Mill Hopper/' a sink hole exceeding 100 feet in depth, is an example. 
The. southeastern part of this county, like the western part, has 
been affected by erosion although under somewhat different condi¬ 
tions. From this part of the county the drainage originally passed 
through Orange Creek to the St. Johns River. The first lowering of 
the surface level was therefore by mechanical wear. In the course 
of time, however, Orange Creek eroded its bed until it approached 
the limestone. Sink holes then formed through which the water 
enters the underlying limestone. Phosphate deposits are scarcely 
to be expected in this type of country as the disintegration of the 
formations above the limestone has not been complete. 
The same principles have operated in determining the topography 
of the other counties of the limestone belt. The hard rock phosphate 
belt represents the area in which the formations lying above the 
Vicksburg Limestone have almost entirely disintegrated. The Lake 
Region and the belt of clay hammock lands including shallow flat- 
bottomed lakes and disappearing streams, are transition stages. 
The Alachua Clays of Tliocene age are lake deposits wdiich very 
probably accumulated while the area in which they occur was pass¬ 
ing through the topographic stage in which lakes existed. The hard 
rock phosphate deposits accumulated in their present form during 
the progress of erosion, the phosphoric acid, taken in solution by 
waters percolating through the surface formations, having reaccu¬ 
mulated at a lower level. 
INFLUENCE OF DRAINAGE ON SOILS. 
The soils are affected by the drainage conditions in various im¬ 
portant ways, to only a few of which it will be possible to refer in 
this paper. 
ORGANIC MATTER. 
The organic matter content of virgin soil is controlled to a large 
extent by the drainage, together with the atmospheric and climatic 
conditions. Moisture, owing to the extent to which it retards oxida¬ 
tion, is a great preservative of organic matter. Muck, as has been 
elsewhere stated, accumulates only where the amount of water in 
or over the soil is sufficient to retard the decay of the vegetation. 
On the other hand, where the drainage is good and the soils exposed 
to the direct rays of the sun, the organic matter natural to the soil 
oxidizes and may disappear. 
THE COLOR OF SOILS. 
The color of soils, which is an important guide in soil classifica- 
