Il8 FLORIDA GEOLOGICAL SURVEY-NINTH ANNUAL REPORT. 
dense; the processes of decay are rapid, and organic acids are pres¬ 
ent in the surface water. All of these conditions are favorable to 
disintegration by solution. The large amount of water which en¬ 
ters the earth in the northern part of this area finds its exit through 
large springs along the. coast, thus establishing a definite system of 
underground circulation. 
That underground solution under these conditions is effective 
as a disintegrating agency is shown not only by the topographic 
forms that have resulted, but also by the character of the water 
itself. Upon entering the earth the rain water is practically free of 
solids in solution, but upon reappearing from the limestone, it car¬ 
ries a heavy load of solids in solution. Under the conditions which 
prevail in this area solution in the limestone is rapid and the land 
forms in the northern and the eastern part of the area owe their 
form chiefly to this agency modified by surface wash and other 
minor agencies. 
LAKE BASINS AND LAKES. 
Among the most pronounced of the topographic features of this 
area are the numerous large and small basins, many of which are 
now occupied by lakes. These basins, the largest of which are 
Iamonia, Jackson, Miccosukee and Lafayette, have resulted from 
solution in the underlying limestone, accompanied by partial re 
moval of the overlying sands and clays. Each basin has an individ¬ 
ual history which may be . followed to some extent. The lakes and 
lake basins are largely confined to the northern part of the area in 
Leon and Jefferson counties. 
The origin of these lake basins is a part of the history of the 
development of the topography of the region. In this development 
both mechanical erosion and solution have had a part. A first step 
in the process of erosion is the. development of stream channels and 
valleys, largely through mechanical erosion. In addition to mechan¬ 
ical erosion, solution by underground water is effective, especially 
in regions underlaid by limestones. 
That the amount of limestone carried away in solution in under¬ 
ground water is great may be determined by the analysis of the 
water of some of the large springs coming from the limestone. 
From an analysis of water of several springs it has been estimated 
that the limestone springs of Florida carry on an average about 219 
