61 
we find it mixed with blende, a zinc ore which is very trouble- 
some to the lead smelters. Specimens from the Welsh mines 
which contain much blende are marked “Poor Ground.” A good 
specimen of fluorite shown here, illustrates another common 
associate of galena in the English mines, as do also the speci- 
mens of calcite and galena. Some of these ores, as for example, 
that from Snail Beach, are from mines formerly worked by the 
Romans. 
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. 
The gold ores of Great Britain may be found in Case 3, 
across the hall. 
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 sufficient lead and silver to yield 
a good profit. 
CASE 20, REAR. — Silver-lead ores, Spain and New South 
Wales. 
CASES D, F, G, H, I AND J. — Illustrate the extraction 
of gold, silver, lead and copper from their ores. Out of a multL 
tude of processes used, eight of the more typical ones are illus- 
trated. 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 
