THE FLORIDA PHOSPHATE DEPOSITS.

dry mines and usually reach to the bottom of the phosphate formation in places encountering the limestone.
In the southwestern part of Marion County and in Citrus County the hard rock phosphate-bearing formation reaches its maximum thickness. The underlying limestone dips in passing to the south, and is ordinarily encountered: at a considerable depth from the surface. Many of the phosphate pits in this section are worked as dry mines to the underground water level and afterwards as dredge mines to such depth as the dipper will reach. Some of the pits on higher lands are mined as dry mines only.
The pit at the Dunnellon Phosphate Company plant No. IO was one of the first pits regularly worked in the phosphate section and has been continuously in operation for the past twenty years. This mine is operated by a dredge. The bottom of the phosphate is not reached in this pit and the full thickness of the formation at this place has not been determined.
CITRUS COUNTY.
The conditions in Citrus County are in a general way similar to the conditions in the vicinity of Dunnellon in Marion County. The underlying limestone is only occasionally seen in the pits in this section. It is, however, frequently reached in the dredge operations below the water level. The surface of the limestone wherever seen projects as rounded peaks similar in character to the conditions further north. There is on an average more clay to be seen in the phosphate formation in this section than in the northern part of the field. In a few instances, notably that of the pit of the Istachatta Phosphate Company, the water level is within a few feet of the surface and the phosphate formation is entirely submerged. Only the pale sands of the overburden are here visible.
HERNANDO COUNTY.
Phosphate is being produced in Hernando County in the vicinity of Croom. The mine in operation here is a dredge mine. The relation of the phosphate formation to the underlying limestone as seen in an abandoned pit several miles west of Croom is the same as that in other parts of the phosphate section, the limestone projecting as rounded peaks. The material above the phosphate stratum consists largely of incoherent sands. The usual gray phosphatic sands weathering purple on exposure are seen sur-rounding the phosphate rock. In the mines near Groom a considerable amount of clay is associated with the phosphate.