64 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
tions, and the character of the sub-soil. In some sections the under¬ 
lying sandy clay is found at a depth of one to two feet. In these 
areas if well drained the clay usually contains iron pebbles and is 
oxidized red in color. Elsewhere the qlay lies from three to six or 
more feet beneath the surface ,and in the extremely sandy soils the 
clay lies at an undetermined depth. 
The superficial sands which form the top soils of the upland pine 
lands have very generally been held to be a formation distinct from 
and later than the underlying material. This view the writer be¬ 
lieves untenable. The parent formation of the soil is the underlying 
sandy clay, the dinistegration of which has given rise to the sands 
according to the usual processes of soil formation. 
The depth to which the sandy clay has disintegrated is deter¬ 
mined chiefly by the topographic and drainage conditions. Under¬ 
ground water is the chief disintegrating agency. The rainfall passes 
into the earth and emerges by seepage along the hillsides. In this 
course of circulation certain of the cementing constituents of the 
sandy clay are dissolved out, and also the minute clay particles, 
which act as a binder, are carried mechanically to a lower depth. 
By this process the covering of loose surface material and soil is 
continuously deepened. 
This process of disintegration is carried on, other conditions 
being the same, most actively where the water table lies several feet 
beneath the surface, and where the sandy clays rest upon limestone, 
or where the surface is sufficiently broken to give good drainage. 
Obviously, however, where the surface is so far broken as to permit 
surface wash, no loose sands accumulate, since they are removed as 
rapidly as formed. It is true, also, that the parent sandy clay is not 
of uniform character, but is more sandy and is more easily disinte¬ 
grated in places, while elsewhere the percentage of clay is greater 
and the disintegration proceeds more slowly. The disintegrated 
stratum in a cross section of a hill may be seen as a rule to follow 
to a degree, the contour being thickest usually on the top of the hill 
unless affected by the surface wash, and thinning out at the sides in 
proportion to the steepness of the slope. 
Some of the very desirable general farming lands are found in 
the belt of rolling pine lands. This is true in particular of those 
soils having clay sub-soil within a few feet of the surface. Other 
sandy soils in which the clay is not within a determinable depth 
are less productive, although even these more sandy soils under 
proper cultivation are made to yield satisfactory returns. In the 
heavier types of soils having a clay sub-soil near the surface the pine 
