260 REPORT OF NATIONAL MUSEUM, 1884. 



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 with coal for the spel- 

 ter furnaces. 



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, ]S\ 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 present 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. 



Sulphur. — The manufacture of sulphuric acid from iron pyrite is a 

 process that has recently been very largely adopted in this country. 

 Various strong prejudices existed formerly against the use of pyrite for 

 this purpose on account of the liability of a small amount of arsenic 

 occurring with the pyrite — this arsenic injuring the acid produced for 

 many purposes. Recently, however, two very important deposits of 

 pyrite which are totally free from arsenic have been developed, and the 

 material is being used quite freely for the manufacture of sulphuric acid. 

 The deposit at Charlemont, Mass., is represented by a collection of the 

 lump and fine ore presented by the Davis Company of Boston. The de- 

 posit at Tolersville, Va., is represented by an extensive series of samples 

 of the lump and fine ore in several varieties, together with many of the 

 associates of the deposit. Presented by Mr. W. H. Adams. 



The pyrite is first roasted to expel its sulphur, which is then con- 



