SECOND ANNUAL REPORT—TOPOGRAPHY AND DRAINAGE. 
33 
A large part of the mineral matter which is thus removed by the 
underground water is carried to the surface; and, entering the rivers, 
is transported to the sea. In an earlier report by this Survey, 1 there is 
an estimate of the amount of solid matter removed in this manner. 
The quantities given were based upon a consideration of the amount 
oil 2 3 Miles 
Fig. 1. Map showing sink holes. 
of mineral matter removed in solution in eight of the large springs 
of the State. These springs emerge from caverns in the underlying 
limestone and they are fed by the rainfall upon the surrounding area. 
The percentage of mineral matter in solution was determined by an¬ 
alysis and the volume of flow was estimated. By this method Dr. 
Sellards estimated that Silver Spring brought to the surface 340 
pounds of mineral matter per minute. While the quantity of matter 
in solution in the water of the other springs varied it was in all cases 
1 Sellards, E. H., A Preliminary Report on the Underground Water Supply 
of Central Florida, Fla. State Geol. Survey, Bull. 1 , 1908, pp. 47-48. 
2g 
