SOME FLORIDA LAKES AND LAKE BASINS.

of the state. On the contrary they are on the uplands, and occur in sections having a hilly or rolling topography. Sinks or openimgs occur through which the water escapes into the underlying formations. These sinks are located ordinarily at the foot of a steep bluff bordering the lake. Around the main sink one finds ordinarily other sinks of more recent formation indicating the manner and direction of enlargement of the basin. The sinks through which the water escapes are variable in depth but reach in all cases to underlying limestones. A channel as a rule leads back from this sink across the lake bottom representing the main channel of flow of %vater to the sink. Aside from this channel the bottom of the lake is relatively flat and level, although slight local depressions occur involving in some instances differences of level, of ten to fifteen feet. The soil in the lake basins varies considerably. In some of the lakes-those which seldom go dry-there is an accumulation of muck or peat formed largely from pond lilies and other aquatic vegetation. Local depressions in the lake often have an accumulation of this material amounting to several feet. Some of the other lakes which frequently go dry have little or no muck except in deIressions which hold water even in dry seasons. Beneath the v suck is usually found light colored sand washed and blown from the neighboring highlands. This sand may be several feet deep in places, elsewhere it is largely absent. Ordinarily a sandy clay occurs beneath the sand.
When these lakes dry up the Water is commonly reported as running out very suddenly. This, however, is usually not the case. As long as the lake has sufficient water to cover the entire basin' the lowering of the water surface proceeds very slowly. Subsequent-ly when the total surface area of the lake becomes much restricted the lowering of the water surface proceeds much more rapidly. This leads to the statement that the water of the lake disappeared suddenly while'as a matter of fact in many cases the water escapes through the sink no, faster and indeed hardly so fast during the dry season as it had been escaping when the lake was full during the season of normal rainfall. It is true, however, that new sinks, occasionally form in the bottom of the lake. In the case of 'the formation of new sinks the rate of escape of the water is increased.
ORIGIN AND HISTORY OF DEVELOPMENT.
The origin of these lake basins is a part of the history of development of the general topography of the region. In 'this development both mechanical erosion and erosion by solution have

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