LEAD AND ZINC ORE 281 



cheaply built and run, individual mills are to be preferred, 

 even though the larger mill be able to make a slight saving 

 per ton in mill charges. It is difficult to supply dirt steadily 

 enough to keep a large mill running, and loss of time is more 

 costly with a large than a small plant. The mills of the 

 district are very simple, and are developed on the prin- 

 ciple of using a rougher jig before cleaning, instead of 

 attempting close sizing. The result is a very great capacity 

 at small cost. The saving is not so close as in a well run 

 sizing mill, but the extra ore saved by the latter is not 

 in this district worth the added cost of saving it. A hun- 

 dred ton mill can be built in the district at a general price 

 of $6,500 to $7,000, and the opening and equipping of a mine 

 costs ordinarily, approximately, $10,000. The mill can be 

 run by four men. To that number must be added a hoister- 

 man and an underground force. The mill and plant are 

 of such style as to be readily torn down and moved 

 when the particular ore body is worked out, and the whole 

 plant is designed for rapid work. Economy is sought in 

 first cost rather than in refinements of efficiency. The whole 

 style of equipment and the methods of mining and milling 

 are designed to meet the conditions of shortlived individual 

 deposits of low grade ore. 



The higher cost of running small plants, as compared 

 with mines operated on a large scale, comes from the expen- 

 sive methods of generating and distributing power, but it 

 is the opinion of Mr. Bain that, with modern methods of 

 power transmission, this difficulty can be overcome by the 

 development of central power plants. 



Though the actual operation of the mines is to some 

 extent still conducted on a small scale, the tendency toward 

 combination has not been without effect upon the zinc lead 

 mining industry. Both the productive capacity and the 

 consumptive demand for spelter have been centralized in 

 a striking manner. Upward of 50 per cent of the consump- 

 tion of spelter in the United States is for the purpose of galvan- 

 izing iron, w^hich business is now chiefly in the hands of the 

 constituent companies of the United States Steel cor})oration. 

 The manufacture of sheet zinc is in the hands of four com- 



