In the center of hall, arranged in two cases, is a collection of 
gold nuggets from Kittitas County, Washington, with views of 
California placer mining, showing method used in 1849, and the 
present system of hydraulic mining, which consists in the disin- 
tergration of the auriferous alluvia, by propelling a heavy jet of 
water under pressure upon the bank, and in washing off the gravel 
in sluices in which is distributed mercury. The gold forms an 
amalgam and remains caught. 
SILVER. 
Cases 6, 7, 8, 9, and 10. — Silver ores. 
Silver occurs in nature in its native state, often beautifully 
crystallized in a variety of forms, of which one of the most com- 
mon is dendritic — tree-like. The common silver minerals are argen- 
tite, stephenite, pyrargyrite, proustite, cerargyrite. Tetrahedrite 
(gray copper), properly considered a copper mineral, may be in- 
cluded in the list, as a percentage of its copper is frequently 
replaced by silver. The gangue in which the ores occur is made 
up of a great variety of minerals, quartz predominating as a rule. 
Lead minerals are usually found with those containing silver. 
Case E. — Silver ores. 
silver=lead ores. 
Cases 11, 12, 13, and 14. 
These ores contain the lead minerals associated with one 
or more of the silver minerals. Argentiferous (silver-bearing) 
galena is the most common lead mineral entering into the compo- 
sition of silver-lead ores. 
Cases F and G. — Metallurgical products resulting from 
the treatment of gold, silver, and lead ores. 
Case H. — The Roessler-Edelmann desilverizing process. 
Samples of materials and products. 
