62 
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 subsequent operations, and so on until the 
final products are shown. It is thus possible for the visitor to 
follqw readily each step of the operation. 
CASE D. — Specimens illustrating successive stages in the 
processes of copper smelting by reverberatory furnace, and by 
blast furnace. Out of many processes in use two have been se- 
lected: 1. The antiquated but classical “Swansea” method, or re- 
verberatory process, as formerly in use in Wales. 2. A modern 
combination of blast furnace and reverberatory process, as con- 
ducted in Omaha, Nebraska. There are a multitude of other pro- 
cesses adapted to different ores and conditions of labor, supplies, 
etc., but these two illustrate the underlying principles. 
CASE F. — The Cyanide process for the extraction of gold 
from low grade ore as carried out at Mercur, Utah. This pro- 
cess depends upon the solution of the gold from the ore by a 
dilute solution of cyanide of potassium and precipitation by 
metallic zinc. The case also contains a collection of concen- 
trates from gold and silver ores, illustrating the process of en- 
riching ores before smelting by the removal of much of the worth- 
less material by mechanical means. 
CASE G. — Extraction of gold as practiced at the Argo 
Smelter, Colorado. This is a type of the processes where the 
gold is collected in copper by smelting and then isolated by a 
process of leaching or solution. 
CASE H.— Extraction of silver and lead as practiced in 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 oDcxations. 
CASE L — 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 gener- 
alized forms of the two most important smelting processes. 
CASE J. — Extraction of gold, silver, lead and copper as 
practiced in the Oberharz, Germany. As with the process illus- 
trated in Case G, the apparent complexity is due to many repe- 
titions of few processes. 
