6o 
associate of galena in the English mines, as do also the specimens 
of calcite and galena. Some of these ores, as for example, that 
from Snail Beach, are from mines formerly worked by the Ro- 
mans. 
Note the general absence of “carbonates” and the fresh un- 
decomposed appearance of the specimens. This is also true of 
the Spanish and German ores. Carbonate and disintegrated ores 
occur near the surface where air and atmospheric waters have 
acted and formed them from the sulphides. These mines having 
been long worked, most of the superficial ores have been removed, 
so that now only the sulphide ores occurring at great depths are 
mined. 
Cases 17, and 18, Rear, — Silver-lead ore, New Mexico. 
The principal ores of this class come from the Magdalena Moun- 
tains. They run low in silver, averaging only about 8 oz. per ton, 
and the percentage of lead is also low. Here may be seen speci- 
mens of the “sand carbonate” ore, which crumbles to powder 
when handled. 
Cases 19, Front, and 20, Front. — Lead ores from Germany. 
Some of the specimens here are especially instructive as showing 
the characteristic structure of veins. The different minerals are 
arranged in bands or layers, the metalliferous layers alternating 
with those of quartz, barite or fluor spar. 
Case 19, Rear, — Silver-lead ores, Greece. Unique among 
these are the slags of Laurium, which are worked by the Greek 
Metallurgical Company. The mines of this locality had been 
operated by the Greeks from the time of Themistocles up to the 
first century, A. D. Owing to the imperfect methods which they 
used, however, the slags produced retained appreciable quan- 
tities of metal. The modern company, collecting these slags and 
using them as ores, extracts sufi&cient lead and silver to yield a 
good profit. 
Case 20, Rear, — Silver-lead ores, Spain and New South 
Wales. 
Cases F, Q, H, 1 and J. — Illustrate the extraction of gold, 
silver and lead from their ores. Out of a multitude of processes 
used, six 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 speci- 
mens of the materials formed from it by the first operation of 
