SOME FLORIDA LAKES AND LAKE BASINS.

ground water goes on more rapidly above the level of permanent underground water than below this level. The term "belt of weathering" is commonly applied to that part of the earth's crust lying above the underground water level; while the term "belt of cementation" is applied to that part lying immediately below this level. According to Van Hise "the most characteristic reaction ot the belt of weathering is, solution. In contrast with this the most characteristic reaction in the belt of cementation is deposition in the openings of the rocks."* The rapid solution in the belt of weathering is due to a number of causes. First of all the water in this part of the earth's crust moves freely, while in the belt of cementation the water often moves very slowly. Moreover water is capable under given conditions of carrying a definite amount of mineral solids in solution and as the water from the surface enters the earth with little or no load, until it becomes saturated it takes materials into solution readily.
In accordance with this principle it is found that the largest of these basins are, as a rule, reduced practically to the level of un-derground water. Many of the smaller basins, it is true, have not r-ached the permanent water level, and stand at varying heights above that level. The relation of the basins to the underground water has a practical bearing and will be referred to again in connection with methods of drainage of the lakes.
DESCRIPTIONS OF TYPICAL LAKES.
LAKE IAMONIA.
Lake Iamonia lies near the north line of Leon County. The lake basin is irregular in outline, but has an average width of from one to one and one-half miles. The total length of the lake is from twelve to thirteen miles., At its west end the lake basin connects with the swamp of the Ocklocknee River. During flood seasons the river overflows into the lake. Similarly a high stage in the lake results in an overflow into the river. Small tributary streams enter the lake from both the north and the south side as well as from the east end. The tributaries are small flat-bottomed streams which are dry, except during the rainy season. The lake fluctuates much according to the rainfall. The lake basin when full covers an area of about 65oo acres. Except at the west end, where
*Treatise on Metamorphism Mon. U. S. Geol. Survey, XLVII, p. 165, I904.

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