70 The Phosphates of America. 



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 River and 

 its tributaries. 



As we have already remarked, the work of exploration or pros- 

 pecting has now extended all over the State in each of these vari- 

 eties of the formation ; actual exploitation on the large scale by 

 regular mining and hydraulic methods has also been commenced 

 at various points ; and we have been able to make a very careful 

 study of the workings on several occasions, with the result that the 

 theories we first formulated have been in every way confirmed. 



In several of the mines, notably in those of Marion and Ci- 

 trus counties, there are immense deposits of phosphatic material, 

 proved, by actual experimental work, to extend in many cases over 

 uninterrupted areas of several acres. The deposits in each case have 

 shown themselves to be combinations of the "original pocket" and 

 the " mound " formation, and the superincumbent material, or over- 

 burden, is principally sand, and may be fairly said to have an aver- 

 age depth of about 10 feet. The phosphate immediately under- 

 lying it is sometimes in the form of enormous bowlders of hard 

 rock, cemented together with clay, and sometimes in the form of a 

 white plastic or friable mass resembling kaolin, and probably pro- 

 duced by the natural disintegration of the hard rock by rolling, 

 attrition or concussion. The actual thickness of the deposits is 

 too variable to be computed with any accuracy into an average, 

 but in one case which specially interested us, the depth is 50 feet, 

 and only a little over two acres of the land have already yielded 

 more than 20,000 tons of good ore, without signs of exhaustion. 



Directly outside the limits of these combined "pockety" and 

 " mound " formations the deposits of phosphate seem to abruptly 

 terminate, and to give place to an unimportant drift, which some- 

 times crops out at the surface, and which may be followed in all 

 directions over the immediate vicinity without leading to another 

 pocket of exploitable value. 



Since the same geological phenomena are prevalent in nearly 

 every section of the country, with the exceptions of Polk and 

 Hillsboro counties, where they are somewhat modified, we consider 

 ourselves, in view of these facts, warranted in declaring that the 



