HALL 80. 
WEST DOME. 
Beneath the center of the dome stands a statistical cclurrm, 
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 the year (31,536,000) will give the annual product. This 
column was built according to data given by the United States 
Geological Survey. In the four niches are pyramids of ore, con- 
taining: 
No. 1. — Gold and Silver Ores. 
Gold and silver ore. State of Washington, U. S. A. 
Silver ore, from New South Wales. 
No. 2. — Tin Ore. 
‘Cassiterite, or tin oxide, in micaceous schist, from New South 
Wales, Australia, and South Dakota, U. S. A. 
No. 3. — Iron Ore. 
Red Hematite, from Wyoming and Minnesota, U. S. A. 
No. 4:. — Copper Ores. 
Bornite, from Cape Colony, South Africa. 
Chalcopyrite, from New South Wales, Australia. 
The four large specimens surrounding the column are respect- 
ively: 
No. 3. — Calamine (silicate of zinc), from Arkansas. 
No. O. — Silver ore, from New South Wales, Australia. 
No. 7 . — Iron ore (red hematite), from Minnesota. 
No, 8 . — Iron Pyrite (sulphide of iron), Quebec, Canada. 
