The Phosphates of America. 65 



said to be very fertile. When uncultivated, however, they are 

 covered with a dense wild growth of vegetation characteristic of 

 the swamp. 



Without pausing to consider the climatic conditions, which are 

 sufficiently well known and which, besides, are outside the scope 

 of our work, and passing at once to the prominent geological as- 

 pects, we may say that the entire State of Florida appears to us to 

 be underlaid, at greatly varying depths, with upper eocene lime- 

 stone rock, and that its first emergence must, in our opinion, be 

 consequently dated from that period. We have based this opinion 

 on the careful examination of many artesian wells that have been 

 practised in several directions, and it is well sustained by the one 

 at Lake Worth, which was completed in June, 1890, and of which 

 the following detailed particulars have been published by Mr. N. 

 II. Darton, of the United States Geological Survey : 



0-400 feet. Sands with thin layers of semi-vitrified sand at 50 and 

 60 feet. 



400-800 ' Very fine-grained soft, greenish-gray quartz sand, con- 

 taining occasional foraminifera and water-worn shell 

 fragments. 



800-850 " No sample. 



850-860 " White sands, with abundant foraminifera of four or five 

 species. 



860-904 " No sample. 



904-915 " Gray sands containing sharks' teeth, small water-worn 

 shell and bone fragments, sea-urchin spines and lithi- 

 fied sand fragments. 



915-1000 " No sample. 



1000-1212 " Samples at frequent intervals. Vicksburg limestone, 

 containing orbitoides in abundance throughout, to- 

 gether with occasional undeterminable fragments of 

 molluscan casts, corals and echinoderms. It is a 

 creamy-white, hard, homogeneous limestone through- 

 out. 



Nor do we rely upon the artesian wells alone, for the Vicks- 

 burg limestone also appears as an outcrop at the surface in many 

 localities, and has been specially noticed in Wakulla and Franklin 

 counties, west of Tallahassee, in Marion and Citrus counties, in 

 Tampa Bay, and on the banks of the Manatee and Caloosahatchee 

 rivers. 



In the opinion of Mr. N. II. Darton, above mentioned, the phos- 

 phates of Florida belong to three formations, distinctly separate 

 stratigraphically, and each represents a long interval of geologic 



