I 



THE WASTE AND CONSERVATION OF PLANT FOOD. 229 



a considerable height, the process of denudation by the action of water 

 commenced. Then there was a subsidence, and the peninsuhi again 

 passed under the sea and was covered with successive layers of sand. 

 The limestones during this process had been leached by rain water, 

 containing an excess of carbonic acid. In this way the limestones 

 were gradually dissolved, while the insoluble phosphate of lime was 

 left in suspension. During this time the bones of the animals before 

 mentioned, by their decomposition, added to the phosphate of lime 

 present in the underlying strata, while some were transformed into 

 fossils of phos])hate of lime, just as they are found to-day in vast 

 quantities. 



Wyatt ' explains the phosphate deposits somewhat differently. Ac- 

 cording to him, during the Miocene submergence there was deposited 

 upon the Upper Eocene limestones, more especially in the cracks and 

 fissures resulting from their drying up, a soft, finely disintegrated cal- 

 careous sediment or mud. The estuaries formed during this jieriod 

 were swarming with animal and vegetable life, and from this organic 

 life the phosphates were formed by decomposition and metamorphism 

 due to the gases and acids with which the waters were charged. 



After the disappearance of the Miocene sea there were great disturb- 

 ances of the strata. Then followed the Pliocene and Tertiary periods 

 ajid Quaternary seas with their dej)osits and drifts of shells, sands, 

 clays, marls, bowlders and other transported materials, supervening in 

 an era when there were great fluctuations of cold and heat. 



By reason of these disturbances the masses of the phosphate deposits 

 which had been infiltrated in the limestones became broken up and 

 mingled with the other debris and were thus deposited in various 

 mounds or depressions. The general result of the forces which have 

 been briefly outlined was the formation of bowlders, phosphatic debris, 

 etc. Wyatt therefore classifies the deposits as follows : 



(1) Original pockets or cavities in the limestone filled with hard and 

 soft rock phosphates and debris. 



(2) Mounds or beaches, rolled up on the elevated points, and chiefly 

 consisting of huge bowlders of phosphate rock. 



(3) Drift or disintegrated rock, covering immense areas, chiefly in 

 Polk and Hillsboro counties, and underlying Peace Eiver and its tribu- 

 taries. 



N, H. Darton, of the United States Geological Survey, ascribes the 

 phosphate beds of Florida to the transformation of guano.^ According 

 to this author two processes of decomposition have taken place ; one of 

 these is the more or less comi)lete reijlacement of the carbonate by the 

 phosphate of lime; the other is a general stalactitic coating of phos- 

 phatic material. Darton further calls attention to the relation of the 

 distribution of the phosphate deposits as affecting the theory of their 



' Engineering au<I Mining Journal, August 23, 1890. 

 sAmer. Jour, of Science, Vol. 41, February,1891. 



