GEOGRAPHY OF CENTRAL FLORIDA 139

 Sand abounds nearly everywhere, and the pure white variety, .such as characterizes the scrub, ought to be well suited for the manufacture of glass. Sand-lime brick is made at Lake Helen, in Volusia County.
 The marl in low hammocks and the shell mounds are used to some extent for road-making. Gypsum is found in a few low hammocks, but apparently not in commercial quantities, unless in the western part of Sumter County.*
 Peat abounds in the lake region and occurs in most of the others, but has been little used as yet. It was discussed at considerable length in the Third Annual Report, which the interested reader can consult for details.
 Artesian water is easily obtained anywhere in the area, but it does not rise above the surface except near the coast and larger rivers and lakes, and at a few other aces at low elevations. The highest artesian pressure found in the State is along the Indian River in southern Brevard County, where the water rises about 50 feet above sea-level, and is used in a small way for running dynamos, etc. Most of the water from deep wells contains considerable salt, lime, sulphur, etc., but hardly ever enough to make it unfit for drinking purposes, except in some places near the upper St. John's River, where the salt content is excessive. In the lime-sink region, however, the water. is often too "hard" for boiler purposes, and water-softeners are used by the railroads. Rain-water cisterns for private residences are used where the water is too deep to be reached by dug wells, as in the lime-sink region, or'too highly mineralized, as in some places along the east coast. Force-pumps are also frequent in the lime-sink region and the higher parts of the lake region, while ordinary suction pumps prevail in the flatwoods.

 *The latest account of the Florida gypsum deposits, containing references to important earlier papers, is by R. W. Stone in "Mineral Resources of the United States for 1918" (U. S. Geological Survey), part 2, pp. 293-296.