DEPARTMENT OF GEOLOGY 
57 
mine, Dolgelly', Wales, is worthy of special attention both on 
account of its completeness and of the character of the ore. 
The gold is nearly all free, and much of it is visible to the eye. 
Specimens of ores from various parts of the mine are shown, also 
specimens of the country rock. 
The silver ores of Greece are represented by a unique series 
from Laurium, including slags left by the ancient smelters which 
are now mined and smelted anew. The mines of this locality had 
been operated by the Greeks from before the time of Themistocles 
up to the first century, A. D. Owing to the imperfect methods 
used, however, the slags produced retained appreciable quan- 
tities of metal. A modem company, collecting these slags and 
using them as ores, extracts sufficient lead and silver to yield a 
profit. 
A series of lead-silver ores from Germany is especially instruc- 
tive, as it shows the characteristic structure of veins. The 
different minerals are arranged in bands or layers and the metal- 
liferous layers alternate with those of quartz, barite, or fluor spar. 
African localities are represented by the banket of the 
Transvaal, and ores from various parts of Rhodesia. 
Several series of metallurgical products illustrate the extrac- 
tion of gold, silver, lead, and copper from their ores. Out of a 
multitude of processes used, eight 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 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 subsequent 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. The processes illus- 
trated are: 
I. Copper smelting by the reverberatory furnace and by 
the blast furnace. Out of many processes in use two have been 
selected; (a) The antiquated but classical “Swansea” method, 
or reverberatory process, as formerly in use in Wales. (6) A 
modem combination of blast furnace and reverberatory pro- 
cess, as conducted in Omaha, Nebraska. There are a multi- 
tude of other processes adapted to different ores and conditions 
of labor, supplies, etc., but these two illustrate the underlying 
principles. 
