THE ARTESIAN WATER SUPPLY OF EASTERN FLORIDA.

Ville, at which place the Vicksburg is reached at approximately five hundred feet from the surface. The wells at Jacksonville, the deepest of which reach a total depth of something over a thousand feet, do not so far as the records show pass entirely through the Vicksburg.
The formations lying above the Vicksburg are less characteristic lithologically and are not easily differentiated. The surface deposits include both recent and Pleistocene material. During a part of Pleistocene time this section of the state stood at a lower level than at present, permitting the ocean to extend inland some distance beyond the present coast line. 'Conrad* has recorded the occurrence of marine shell deposits of post-Pliocene age along the banks of the St. Johns River at an elevation of from ten to fifteen feet above the present high tide. Conrad also reports a similar post-Pliocene deposit about one-half mile from the bank of the river near the ancient village of Hasard. Marl deposits are said to occur near 'the mouth of the St. Johns River on the banks of Ft. George Inlet. That the depression of the coast during Pleistocene time was general is indicated by the records from several other localities.
Beneath the Pleistocene, Pliocene deposits probably occur over some parts of the county. The total thickness of the Pleistocene and Pliocene, if both are represented, is, however, not great at the fossiliferous Miocene limestone was reached at Jacksonville in the boring at the city well at a depth of 33 feet.
AREA OF ARTESIAN FLOW IN DUVAL COUNTY.
The area of artesian flow in Duval County is indicated on the accompanying map by shading. As will be observed the flowing
area borders the Atlantic coast, Nassau and St. Johns Rivers and extends some distance inland following each smaller stream and tributary. The wells in western Duval County are non-flowing. A topographic map of this section would assist in determining flowing and non-flowing sections, since (the flow is to a large extent correlated with elevation. It is to be borne in mind, however, that artesian water depends primarily upon the structure of the underlying formations and these formations are liable ,to variations- of which there is no surface indication. For this reason while the map indicates the area of probable flow the exact limits of the area are best determined by drilling....
*Conrad, T. A. Am. Journ. Sci. (2) II, .38, 1846.

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