The Phosphates of America. 73 



phosphate, and about one hundred and twenty-Jive thousand ions 

 debris and seconds, containing from sixty to sixty-five per cent, 

 of bone phosphate. 



The capriciousness exhibited in this instance is not at a'il ex- 

 ceptional or singular, but has been confirmed in several others, and 

 it is not quoted in any deprecatory sense, but as an example of the 

 necessity for exercising unusual care and discretion when making 

 expert examinations. 



In the case of the "pebble" or "drift" deposits this caution 

 needs not perhaps to be so extremely precise, for, as we have already 

 stated, these are marked by unusual regularity in the chief centres 

 of their occurrence. The extensive area in which they have been 

 found may be roughly said to take its point of departure in Polk 

 County, a little to the south of Bartow, and thence, with a gradually 

 narrowing tendency, to practically continue to within very short 

 range of Charlotte Harbor. 



As will be seen from the map, the country is very flat and 

 swampy ; is intersected at frequent intervals by the Aiafia, Mana- 

 tee, Peace and other rivers, and by numerous small rivulets and 

 streams. 



Pit-sinking and boring is now going on over an area of many 

 hundreds of miles, and so far as we have been able to ascertain, the 

 prospectors have succeeded in demonstrating that this section of 

 Florida \s virtually underlaid with a nodular phosphate stratum 

 of a thickness varying from a few inches to thirty feet, and covered 

 by an overburden that may be fairly averaged at about eight feet. 



The actual chief working centre for " pebble " phosphates is 

 Peace River, which rises in the high lake lands of Polk County 

 and flows rapidly southward into the Gulf of Mexico. Its course 

 is extremely irregular, and its bottom is a constant succession of 

 shallows and deep basins. 



Lakes Tsala-Opopka and Chillicohatchee and Pains and Whid- 

 den creeks are its chief tributaries and the main sources of its phos- 

 phate deposits ; the pebbles being washed out from their banks 

 and borne along their beds by the torrential summer rains. 



The exploitation of the pebbles is performed, as illustrated, by 

 means of a ten -inch centrifugal steam suction pump placed upon a, 

 barge. The pipe of the purnp, having been adjusted by ropes and 

 pulleys, is plunged ahead from the deck into the water. The mix- 

 ture of sand and phosphate sucked up by it is brought into revolving 

 screens of varying degrees of fineness, whence the sand is washed 



