75 
Case 16, Front. — Silver-lead ores, Mexico. Note the 
collection of carbonate ore from Minas Viejas, Villaldma, as 
showing how widely ores of this class may vary in appearance. 
Case 17, Front. — Silver-lead ores, British Columbia. The 
localities represented lie just north of the State of Washington, be- 
tween the Cascade and Rocky ^Mountains, at the latitude of Van- 
couver Island. 
Case 18, Front. — Lead ores, Great Britain. The speci- 
mens illustrate well Some of the common associations of galena. 
While in the Colorado ores the galena is commonly associated with 
pyrite, here we find it mixed with blende, a zinc ore which is very 
troublesome to the lead smelters. Specimens from the Welsh 
mines which contain much blende are marked “ Poor Ground.” A 
good specimen of fluorhe shown here, illustrates another common 
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 
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 oc- 
cur 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 19, Front, and 20, Front.— Lead ores from Ger- 
many. Some of the specimens here are especially instructive as 
showing the characteristic structure of veins. The different min- 
erals are arranged in bands or layers, the metalliferous layers al- 
ternating with those of quartz, barite or fluor spar. 
Case 19, Rear. — Lead ores, Greece. Unique among these 
are the slags of Laurium, which are worked by the Greek Metallur- 
gical 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 quantities of metal. The 
