GEOGRAPHY OF CENTRAL FLORIDA 167

 The water of most of our lakes is comparatively clear, and some in Seminole and Orange Counties are used for city water supplies in preference to the hard and sulphurous artesian water. The clearest lake of any size in central Florida is probably Lake Weir, in the southern part of Marion County. Two or three small cof feecolored branches enter its eastern end and tinge the water there a little, but its western end, which is in the lime-sink region, is sc clear that one can see the bottom where it is several feet deep. This is probably correlated with a small amount of limestone in solution, for a species of mussel (Unio Cnninghami) is common in the western part of the lake.
 Ponds and swaps. Shallow ponds, which may dry up cornpletely in dry seasons, varying in size from perhaps one to a hundred acres, abound in the flatwoods and are fairly common in the lime.-sink region. They nearly always have considerable vegetation in them, sometimes only maiden-cane, wampee, bonnets, and other herbs, but more often bushes or trees or both. (Additional details are given in the chapter on vegetation.)
 The various types of marshes and peat bogs have been pretty fully discussed in the Third Annual Report, and some of them will be referred to farther on under the head of vegetation. The same might be said of swamps, which are not very extensive in central Florida.
 Springs. There is perhaps no equal area in the United States, that has more large springs than central Florida. Most of them are the points of emergence of subterranean creeks or rivers, which usually come up through one or more irregular openings in the bottom of bowl-like basins. They are most common in the lime-sink region and near its edges, but there are also several in the Gulf hammock region and a few in the lake region, particularly near the St. John's River and on the edges of the great Wekiva River swamp in Seminole and Orange Counties.
 Silver Spring (fig. 8), a few miles east of Ocala, is one of the largest springs known, about 200 feet wide and 35 feet deep. One discharge measurement made of it gave about 150,000 gallons a minute, or 333 cubic feet a second, and another, probably some distance down stream, about twic e as much. The stream or "run"' issuing from it is so large that small steamers from the Ocklawvaha River can come right up into the spring; and this has been a fa-,


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