SOME FLORIDA LAKES AND LAKE BASINS.

Solution in the limestone occurs both above and below the water line, but chiefly above. As solution continues the overlying material is no longer able to support its own weight and caves in, forming a sink or natural opening from the surface to the limestone. As long as this sink remains open, water passes through and escapes readily into the limestone. Drilled or dug wells serve as artificial openings to the same formation. Wells drilled into this limestone will serve either as supply wells from which water may be pumped or as drainage wells into which water may be conducted. It is generally the case that a well entering this formation that can not be appreciably affected by pumping, will also conduct water readily. If the openings at the mouth of the well are sufficiently free to permit ready flow to the well when being pumped, they are, conversely, sufficiently open to allow the water to spread rapidly from the well when used as a drainage well. The amount of water held in the pores and cavities of the limestone is so great that the water level is not appreciably affected either by the water removed when a well is being pumped, or by the water added when a well or sink is used for drainage purposes.
Attempts to enlarge existing sinks or to re-open sinks that have become clogged have usually proved futile. It is doubtless true that the opening through sinks is a more or less winding channel and to re-open this when clogged with debris is difficult.
Better success has been obtained by dug or drilled wells. Where the underlying porous formation into which the well is to be drained lies near the surface, dug wells can be used to advantage and may be preferable. Dr. H. Bjystra has used this method in draining a small lake or "prairie" on his farm near Brooksville, Florida. At this locality the cavernous limestone lies near the surface and is reached by relatively shallow wells. The one difficulty experienced as reported by Dr. Bjystra is the fact that during the summer rainy season in one or two instances the rainfall has been so heavy within a short space of time that the wells were unable to carry away the water as fast as it fell, the result being temporary overflow of the farm and serious injury to growing crops. It is probable that this danger can be removed in this instance by digging additional wells.
Drilled or bored wells have been in some instances notably successful. An advantage in the drilled well is that it can be put down to any required depth. When properly cased and screened drilled wells are permanent. The effectiveness of the well is dependent upon the structure of the formation penetrated. If the water-conducting power of the formation reached by the well is

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