62 BULLETIN 12, UNITED STATES NATIONAL MUSEUM. 



Slag which was made in the smelting of this last third matte is rep- 

 resented by the last slag analysis above. 



This region is represented by two very complete collections, made by 

 Mr. J. F. Kemp, M. e., September, 1884. 



St. Joe Lead Works. 



The product of the mines is illustrated by the following specimens 

 of the ore : 



(1) Galena, with a little liraestouc, rich lump ore. (54884.) 



(2) Galena, iu cleavable calcite. (54887.) 



(3) Galena, in compact limestone, characteristic disseminated ore. (54886.) 



(4) Galena, in granular limestone, characteristic disseminated ore. (54885.) 



The disseminated ore is treated in the concentrating mill, as shown 

 by the following scheme, figure 4: 



The material remaining on the top of the sieves " heads " is here called 

 "scrapings," that passing through is called "hutchwork," while the 

 tails are called " chats." 



The ore from the mines is delivered to eight 15-inch by 9-inch Blake 

 crushers; from these it goes to eight 14-inch by 30-inch Cornish rolls, 

 and thence passes over 7-milIimetre screens. The coarse material is 

 returned to the rolls, while the fine is washed to centrifugal pumps by 

 a stream of water. These pumps force the material to an ingenious dis- 

 tributer, which delivers it, without any sorting as to sizes, to the piston 

 jigs. There are thirty-six of these jigs in two rows of eighteen each, each 

 jig having two sieves. The heads from the first sieve of these jigs, called 

 scrapings, is good mineral. The hutchwork passes to a settling box, 

 the settlings of which are purified in an ingenious screw-washer, yielding 

 good mineral, and washings which are united with the settlings from 

 No. 2 settling-box, and go to eighteen eccentric jigs, with 3 sieves each, 

 yielding almost entirely hutchwork. The settlings from boxes Nos. 3 

 and 4 are treated on percussion tables. The overflow from sieve No. 1 

 of the piston jig goes to sieve No. 2, yielding scrapings of i)yrite, which 

 are recrushed, hutchwork and tailings which are known as chats. 

 The mill treats about 800 tons of ore per daj, yielding about 100,000 

 pounds of dressed mineral. The various steps in this process are 

 illustrated by the following specimens : 



(1) Feed for piston jig. (54931.) 



(2) Scrapings from piston jig, sieve No. 1, minerfil. (54932.) 



(3) Hutchwork from piston jig, sieve No. 1. (54925.) 



(4) Mineral from screw-washer. (54922.) 



(5) Feed for eccentric jig, sieve No. 1. (.54929.) 



(6) Hutchwork from eccentric jig, sieve No. 1. (.54928.) 



(7) Hutchwork from eccentric jig, sieve No. 2. (54930.) 



(8) Mineral from bump tables. (54934.) 



(9) Scrapings from [listoii jig, sieve No. 2. (54926.) 

 (10) Hutchwork from piston jig, sieve No. 2. (54927.) 



