274 REPORT OF NATIONAL MUSEUM, 1884. 



The same ore crushed ready for the furnace. 



The silicate and carbonate ore, consisting principally of calimine or 

 hydrated silicate of zinc with a little carbonate of zinc, resulting from 

 decomposition, in lumps as mined, from the Sterling Hill mine, Ogdens- 

 burg, Sussex County, New Jersey. 



The same ore after roasting to expel water and carbonic acid. 



The roasted ore crushed ready for the furnace. 



Anthracite coal used for heating purposes. 



Anthracite coal (fine) to be mixed with the ore in making up the 

 charge to reduce the zinc to the metallic state. 



The mixed charge of Franklinite ore and coal ready for the oxide fur- 

 nace. 



The mixed charge of silicate and carbonate ore for the spelter fur- 

 naces. 



The residuum remaining in the oxide furnace after the extraction of 

 the zinc. 



The oxide of ziuc produced. 



The residue remaining in the retorts after the distillation of the zinc 

 in the spelter furnaces. 



Blue powder, a by-product consisting of a mixture of metallic zinc 

 and oxide resulting from imperfect condensation of the zinc. 



The spelter or metallic zinc produced. 



To these are added — 



The fire-clay from Woodbridge, N. J., used for making retorts. 



A piece of new retort. 



A piece of old retort. 



Old retort ground, to be mixed with the clay in making new retorts. 



The collection from the spiegel furnaces shows — 



The residuum from the oxide furnaces, containing the iron and man- 

 ganese originally \> resent in the ore. 



Limestone used for flux, from Sing Sing, N. Y. 



Anthracite coal used for fuel. 



The slag produced. 



Oxide of zinc deposited in the gas-flues. 



The spiegeleisen produced. 



The collection of specimens is supplemented by photographic views 

 of the principal points about the works* 



COLLECTIONS IN METALLURGY. 



Gold. 



The extraction of the free gold from the auriferous gravel of California 

 by amalgamation : Collection from the North Bloomfield mine, Nevada 

 County, California. 



The extraction of the free gold from the auriferous pyrite in quartz 

 of Colorado, by stamping and amalgamating: Collection from the Bob- 

 tail mill, Black Hawk, Gilpin County, Colorado. 



The extraction of gold from the auriferous mispickel (arsenical pyrites) 



