THE SOILS OF FLORIDA. 
39 
SOILS. 
Soil is the relatively thin covering of fragmental material that 
more or less completely mantles the surface of the earth and serves 
as an anchorage for and contributes to the growth of plants. The 
basis of this material is inorganic, and is derived from the decay and 
disintegration of pre-existing rocks. It consists of mineral particles 
of varying size and of various kinds. With this is included more or 
less organic matter resulting from the decay of vegetable or animal 
life. While the mineral matter usuafly predominates, some special 
soils, as those derived from muck and peat deposits, consist largely 
of organic matter. 
The average soils consist chiefly of the clay minerals, and of sili¬ 
ceous sand and gravel. However many other minerals occur in soils, 
and almost any mineral which is relatively insoluble, and is also not 
readily decomposed may be expected as a soil ingredient. The soils 
are continuously forming by the disintegration of rocks, and after 
being formed are further affected and modified by the topographic, 
climatic, drainage and other conditions to which'they are subjected. 
The readily soluble minerals are largely removed, and the unstable 
minerals are decomposed. Thus in the process of the decay of rocks 
and the formation of soils the sulphides in the rocks are changed 
to the more stable oxides. A soil formed from a limestone consists 
chiefly of the clayey or other impurities of the formation, the car¬ 
bonates which make up the chief part of the limestone, having been 
removed in solution. From the granitic rocks there is removed in the 
process of decay the soluble constituents including the carbonates, 
and the other readily soluble minerals. The resulting soils consist 
of the relatively insoluble minerals which existed in the rock or 
which were formed during the process of decay, including the clay 
and sand. In addition to the removal of the ingredients by solution 
there is also more or less mechanical separation of materials by the 
sorting power of water. This is distinctly so in transported soils, 
and occurs to some extent in residual soils. 
Chemically the soils are complex. Their productiveness depends 
among other things upon the mineral constituents present, the physi¬ 
cal condition of the soil, and the chemical elements available to 
plant growth. 
THE CHEMICAL ELEMENTS. 
About eighty chemical elements have been recognized as present 
in the earth or in the atmosphere surrounding the earth. Of these 
