74 The Phosphates of America. 



"back into the river. The cleaned pebbles are discharged from the 

 screens into scows, at the rate of about twelve tons per hour, and 

 are floated down to the " works," where they are taken up by an 

 elevator to a drying-room and dried by hot air, screened once more, 

 and are then ready for market. The total cost of raising, washing, 

 drying, screening and loading on the cars in execution of orders, 

 is variously estimated at from 50 cents to $2 per ton ; but from 

 special information recently afforded to us by one of the largest 

 operators we are enabled to place it at $1.40, and this, to the best 

 of our knowledge and belief, is the lowest yet recorded in the 

 world's history of phosphate-mining 



The pebbles, when freed from impurities and dried, are of a 

 dark blue color, and are hard and smooth, varying in size from a 

 grain of rice to about one inch in diameter. Their origin is proved 

 by the microscope to be entirely organic, and they are intimately 

 mixed up with the bones and teeth of numerous extinct species of 

 animals, birds and fish. 



There can be no doubt that these river deposits all proceed 

 from the banks of " drift " situated on the higher lands in Polk 

 County, and as a proof of it, if we take Lakeland and Bartow as 

 the centre of these " drift " beds, we shall find that the " pebbles " 

 are all of the same size, and only differ in that they are of a lighter 

 color than those of the river, and that they are imbedded in* a 

 matrix of sand and clay, to which they frequently bear the propor- 

 tion of about twenty per cent, by weight. 



Their separation from this matrix by most of the companies 

 now working is effected in a very crude manner and on a great 

 variety of plans. One of the largest concerns in Polk County em- 

 ploys a floating dipper dredge, the use of which, it claims, is natu- 

 rally indicated by the fact that in this very low-lying section of 

 the State, water springs a few feet below the soil, and thus enables 

 the dredge to work in a canal which it deepens and extends as it 

 removes the material. The entire mass, matrix and all, is brought 

 up to the surface by the dredge and dropped into a species of dis- 

 integrator or crusher. Thence it passes on into a revolving washer 

 mounted on the same barge. From the washer, the matrix and 

 water return to the canal, while the clean nodules are carried by 

 a spiral conveyer to a steam-heated dryer on another barge ; from 

 the dryer they fall into a revolving screen, which removes any 

 remaining particles of adhering sand, and the now marketable 

 phosphate is caught up by elevators and delivered on board rail- 



