622 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [6j 



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 zinc 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 iron and manga- 

 nese. 



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



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 ^orth Bloomfield mine, Nevada 

 County, California. 



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

 Colorado, by stamj^ing and amalgamating : Collection from the Bobtail 

 mill, Black Hawk, Gilpin County, Colorado. 



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

 by roasting and chlorination : Collection from the Del Oro Works, 

 Canada. 



The extraction of gold and copper from auriferous copper ores, by the 

 fusion and electrolitic process : Collection from the works of E. Balbach 

 & Son, Newark, N. J. 



