36 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
tion, is dependent upon chemical reactions which are controlled to a 
large extent by the drainage conditions. The chief mineral stain in 
soils is iron in its varying forms. Those soils and sub-soils that are 
thoroughly saturated with water at all times are likely to be dark 
or drab in color. The dark color is due to the fact that the iron is in 
an un-oxidized or de-oxidized condition. When partly, although 
imperfectly drained, soils assume a mottled appearance, the mottling 
being due to the partial oxidation of the iron. The bright red soils 
are those in which the iron has been thoroughly oxidized and exists 
in the non-hydrated form, hematite. The ochre yellow soils are 
believed to be stained in most cases by the dehydrated iron oxide. 
Those soils which lie on the slopes and are well drained and- are 
rapidly renewed by the addition of soil material from beneath are 
most frequently red in color. On the other hand, the ochre yellow 
soils are found in areas where both drainage and aeration are g,ood, 
but where the conditions are such that there is little or no surface 
wash, and where consequently the renewal of the soil is slow. It is 
probably true that red soils when long exposed to the air and to 
moisture such as is afforded by capillary movement, change over 
to yellow soils, the change in color being due to the hydration of the 
iron oxide. 
The dark color in soils is due in most instances to organic matter 
which accumulates, as explained in the preceding paragraph, under 
moist conditions. 
THE WATER TABLE. 
By the term water table is meant the level at which water stands 
in the soils. Above this level, while the soils may be and usually 
are moist, the moisture is that due to capillary movement of water 
and the soils are aerated. At and below this level the soil is satu¬ 
rated with water and the air is practically excluded. The physical 
and chemical conditions above and below the water line are conse 
quently in marked contrast. Above the line the oxidizing processes 
prevail; below the line de-oxidizing processes prevail. The minerals 
above the water line tend to assume the form of oxides; while below 
the water line the minerals more frequently exist as sulphides or 
sulphates. Above the water line the. movement of water following 
heavy rains is free and solution is active; below the water line the 
movement of water is sluggish and limited and decomposition in¬ 
stead of solution may occur. The importance of the water table to 
the character of the soil in the flatwoods region of Florida has been 
well expressed in the Soil Survey of Jefferson County by G. B. Jones 
and others of the Bureau of Soils as follows:* “A profile of the flat- 
