WATER SUPPLY OP EASTERN AND SOUTHERN FLORIDA. 115 
is an extensive deposit underlying all of Florida and extending 
into adjacent States. In Central Peninsular Florida, from Colum¬ 
bia to Sumter Counties, these limestones are frequently exposed 
at the surface. Passing to the east and south from Central 
Florida they dip beneath the surface, and while nowhere exposed 
at the surface they are reached by all the deeper wells. It is in 
fact from these limestones that the principal water supply of 
Eastern and Southern Florida is obtained. The Vicksburg is very 
characteristic in appearance and structure, and when once seen 
is not likely to be mistaken for any other formation in this part 
of the State. The limestone as seen in well samples has a granu¬ 
lar appearance and may contain many small shells. This phase 
of the limestone is frequently spoken of by the drillers as the 
“coral” formation. As a matter of fact, however, the formation 
contains relatively few corals. After passing one or two hundred 
feet into this formation a more compact limestone is encountered. 
This part of the formation often has a slightly pinkish cast, the 
rock being very hard, and the drilling difficult. While these are 
the general characteristics of the Vicksburg, yet its texture is not 
uniform. . Hard layers usually alternate with soft layers, the 
water supply as a rule increasing as each hard layer is penetrated. 
Not infrequently masses of flint are found imbedded in the lime¬ 
stone which in some instances have given much difficulty in 
drilling. 
While, as already stated, the Vicksburg limestones dip on 
passing to the east and south, yet the dip is not uniform and the 
depth at which it is encountered varies from place to place. 
In the wells at Jacksonville the Vicksburg is reached at a 
depth of from 500 to 525 feet. At Callahan and at Fernandina, 
in Nassau County, although no samples have been obtained, the 
Vicksburg is believed, from well records, to be reached at about 
the same depth as at Jacksonville. 
Along the St. Johns River the Vicksburg maintains a similar 
depth for some distance. At Ortega, seven miles south of Jack¬ 
sonville, the limestone was reached at a depth of about 500 feet. 
At Magnolia Springs, and Green Cove Springs, thirty miles south 
of Jacksonville, and on Black Creek, while no well samples were 
