DEPARTMENT OF GEOLOGY 
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posed placed beside it. The color of rings or other articles of 
jewelry may be compared here with gold plates of the several 
degrees of fineness. 
A collection illustrating the methods of saving gold and 
silver practised by Tiffany and Company, New York, also occu- 
pies a table case. It includes wash water, concentrates from an 
exhaust blower that collects the dust of the shops, pieces of 
flooring of the shops, and shoes worn by workmen. Beside 
each of these are placed buttons of gold and silver obtained 
from articles of size similar to those shown. 
PLATINUM. 
The platinum collections are installed in a floor case in this 
Hall. They include a series of specimens illustrating modes of 
occurrence of platinum from over twenty localities, including 
Washington, Oregon and California, the United States of 
Colombia, and the Ural Mountains. In all of these specimens 
the metal appears in the form of flattened grains often asso- 
ciated with iridium, osmium, palladium, gold, copper, and 
chromite. The grains are usually found in river beds or placer 
deposits. A complete series of rocks and soils bearing plati- 
num, from the Demidoff Platinum mines, Nizhni Tagilsk, Ural 
Mountains, is shown, as well as a series of concentrates pro- 
duced by washing these in order to separate the metal. Some 
unusual uses of platinum are illustrated as follows; Russian 
platinum coin, for a time used as money; coins struck in plati- 
nutn and gilded, which passed for gold in Portugal and Spain 
during the past century, and imitation gold dust made of plati- 
num grains plated with gold. 
Hall 80. 
WEST DOME. 
Beneath the center of the dome stands a statistical column 
giving the bulk of each product of the mines of the United 
States, in 1892, for one second of time. Multiplying this by the 
number of seconds in a year (31,536,000) will give the annual 
product. In four niches in the walls are pyramids of ore, con- 
taining respectively gold and silver ores, tin ores, iron ores, and 
copper ores. 
In addition twenty large specimens of ores are shown here. 
