JV. H. Darton — Record of deep Well at Lake Worth. 105 



The apparent restriction of the rock-phosphate deposits to 

 the western " ridge " of Florida may have some special bearing 

 on their genesis but at present no definite relationship is per- 

 ceived. The aggregate amount of phosphate rock distributed 

 in fragmentary condition in the various subsequent formations 

 is very great, greater by far than the amount remaining in its 

 original position and it is possible that the area at one time in- 

 cluded the greater part, if not all, of the higher portions of the 

 peninsula. As this region apparently constituted a long, 

 narrow peninsula or archipelago, during early Miocene times, 

 it is a reasonable tentative hypothesis that during this period 

 guanos were deposited from which were derived the material 

 for the phosphatization of the limestone, either at the same 

 time or soon after. 



The pebbles of the conglomerate phosphate were undoubt- 

 edly derived from the rock phosphates, for they are identical 

 in appearance and composition and overlap them as a shore 

 deposit. Evidence in regard to the age of the conglomerate 

 formation is very meager. The only organic remains I met 

 with were two imperfect casts of Pectens in the " Chimney 

 rock " near Gainesville. These had a Miocene aspect but the 

 evidence is not by any means conclusive. This u Chimney 

 rock " of Gainesville is a porous sandstone containing a small 

 proportion of pebbles of phosphate rock, lying un conformably 

 above the Vicksburg limestone. It is the structural equivalent 

 of the conglomerate beds of the Polk county region but they 

 may prove not to be identical in age. 



The phosphate deposits of Florida will require careful de- 

 tailed geologic exploration before their relations and history 

 will be fully understood, and it is the purpose of these prelim- 

 inary notes only to throw some light on their more general 

 features. 



Art. XIII. — Record of a deep Well at Lake Worth, southern 

 Florida ; by N. H. Darton. 



In June, 1890, a well was completed at Lake Worth, on the 

 southeastern coast of Florida, which penetrated the great sand 

 mantle and extended down into the Vicksburg limestone to a 

 depth of 1212 feet. It was bored by Mr. J. A. Durst, who 

 has very kindly placed the borings at my disposal. 



Unfortunately, no samples were collected for the first 400 

 feet, and there are several other gaps for which information is 

 lacking. Notwithstanding its imperfections the section is an 



