44 REPORT OF NATIONAL MUSEUM, 1889. 



and Refining Works, New Jersey. This collection is interesting as 

 showing the refining of copper aud separation of the precious metals by 

 the electric current. 



The application of gold is illustrated by 11 specimens showing the 

 manufacture of gold leaf. 



Seven specimens illustrate iridosmine. Of these, 4 show the original 

 sand, and the gold dust, iridosmine, and black sand separated by wash- 

 ing. 



The mineralogy of silver is illustrated by 36 specimens, including all 

 the ordinary silver minerals. The silver ores are divided into milling 

 and smelting ores; these again are subdivided into free milling and 

 roasting milling, aud silver smelting and silver-lead smelting. A. few, 

 such as leaching ores and argentiferous copper ores, do not fall into this 

 classification. Thirteen specimens illustrate the strictly free-milling 

 ores, or such as readily yield to stampiug and amalgamation. These 

 carry mostly free silver or cerargyrite. Twelve specimens illustrate 

 free-milling ores which require the use of chemicals in the pan ; of these 

 8 are charac teristic ores from the Comstock lode. Ores requiring roast- - 

 ing before milling are illustrated by 5 specimens, and a complete series 

 of 19 specimens from the Ontario mine, Park City, Utah. Besides 

 some general characteristic specimens, this includes a section along the 

 fifth level aud two sections across the vein on the sixth level. 



The extraction of silver from roasting-milling ores is well illustrated 

 by two collections made by the former curator. The first, comprising 

 30 specimens from the Ontario mill, illustrates every step iu the process 

 from the time the ore is dumped upon the grizzly until the bullion is 

 shipped by express, and the tailings are turned to waste. The second 

 collection represents in the same full way, with 17 specimens, the opera- 

 tion of the Moulton mill at Butte, Montana. 



The treatment of argentiferous copper ores is illustrated by a collec- 

 tion of 32 specimens from the Argo Works, Colorado. This collection 

 is particularly valuable on account of the assays and aualysis accom- 

 panying the specimens. 



The mineralogy of lead is illustrated with 14 specimens of sulphide, 

 sulphate, and carbonate. Silver-lead ores are illustrated by 57 speci- 

 mens. This series begins with roughly crystallized galena, showing 

 the characteristic cleavage, and follows through several varieties of 

 galena to the beginning of decomposition, resulting in cerussite and 

 anglesite. The association of galena with other sulphides is well illus- 

 trated, and a large collection of characteristic samples of cerussite 

 closes the series. 



The smelting and refining of base bullion is illustrated in collections 

 from the Colorado smelter, South Pueblo, Colorado; the Cheltenham 

 Works, St. Louis, Missouri, and the Kansas City Smelting and Refin- 

 ing Works, Argentine, Kansas. 



The collection from the Colorado smelter contains 59 specimens, 



