82 
modern company, collecting these slags and using them as ores, 
extracts sufficient lead and silver to yield a good profit. 
Case 20, Rear, — Lead ores, Spain. 
Case F. — Concentrates from gold and silver ores, illustrating 
the process of enriching ores before smelting by the removal of 
much of the worthless material by mechanical means. 
Cases G, H, I and J.— Illustrate the extraction of gold, 
silver and lead from their ores. Out of a multitude of processes 
used, five of the more typical ones are illustrated. In general, the 
extraction is carried on by a series of operations. On one side of 
the case is placed the ore, and lines are drawn from it to the 
specimens of the materials formed from it by the first operation 
of extraction. From each of these specimens lines are likewise 
drawn to specimens of the substances formed from them in sub- 
sequent operations, and so on until the final products are shown. 
It is thus possible for the visitor to follow readily each step of the 
operation. 
Case G. — Extraction of gold as practiced at the Argo Smelter, 
Colorado. This is a type of the processes where the gold is col- 
lected in copper by smelting and then isolated by a process of 
leaching or solution. 
Case H.— Extraction of silver and lead as practiced at the 
Unterharz, Germany. 
By following the labels it will be seen that this apparently 
complicated process is resolved into the frequent repetition of 
comparatively few operatior^. 
Case I.—Extraction of lead and silver by the reverberatory 
process and by the blast furnace process. These do not repre- 
sent the process of any particular smelter, but rather are general- 
ized forms of the two most important smelting processes. 
Case J. — Extraction of gold, silver, lead and copper as prac- 
ticed at the Oberharz, Germany. As with the process illustrated 
in Case G, the apparent complexity is due to many repetitions 
of few processes. 
The visitor should now pass to the eastern end of the hall and 
note the following special groups in the center. 
K.— Silver, lead and copper ore. Cordillera Hill silver mine, 
Peelwood, New South Wales. 
Ij, — G old and silver ore, British Columbia. 
