78 The Phosphates of America. 



property, can form an approximately correct idea of the quantity 

 and the quality of material at our command, and can decide with 

 intelligence upon the best points at which to commence industrial 

 operations on the desired scale. 



Our plant is so constructed as to enable us to crush the whole 

 of our rock material to a suitable size, say, 1^-inch ; to pass our en- 

 tire output through washers and screens similar to those we have 

 described in the chapter on South Carolina ; and to finally dry it 

 by hot air, avoiding direct contact with fire. The cost of produc- 

 ing one ton of clean phosphate rock under these conditions, as 

 shown by our practical working experience, averages about $5, and 

 from the fact that the method was based upon and has fully justified 

 the results of a very lengthy series of laboratory experiments, we 

 are enabled to claim for it 



1. That, the product being reduced to a uniform size, 

 the difficulties hitherto experienced in obtaining fair and con- 

 cordant samples on shipment and arrival are materially less- 

 ened, if not entirely obviated. 



2. That the objectionable iron and alumina, being nearly 

 always present in the original sample in the form of clay 

 which is held and secreted in the interstices or cracks of the 

 rock, are nearly all removed by the water and the agitation 

 during the washing process. 



On somewhat similar lines to these, a very ingenious and prac- 

 tical as well as economical method of mining and preparing the 

 land-rock phosphates is that devised by the Jeffrey Manufacturing 

 Company, of Columbus, Ohio, and now being used by some of the 

 larger companies. The rock is hoisted from the quarries by a der- 

 rick, delivered to a crusher, and thence into a system of screens. 

 The first is a dry screen, the second a washing screen and the 

 third a finishing, or rinsing screen ; and the rock is delivered from 

 one wet screen to the other by short elevators, and then taken from 

 the last screen by slow-motion elevator, so as to drain off as much 

 of the water as possible. It is then delivered at the top of a fur- 

 nace having interlapping shelves, under which the flues conducting 

 the products of combustion to the stack are carried. While de- 

 scending from one of these shelves to the other through the hopper- 

 like aperture to the furnace, the rock is either heated to the neces- 

 ary degree to dry it, or, by a retaining device at the bottom, may 

 be kept until thoroughly calcined, after which it is delivered hot 

 to the foot of an elevator. The flue connecting with this elevator 



