1883.] Mining Regions of Southern New Mexico. 157 
time covered by the trachytic flows, It is further found that the 
hard, unyielding strata of limestone and quartzite are fissured 
and cracked to a very great extent, while the more pliable shales 
are not so affected. The argillaceous limestones (/) show fis- 
sures of only small dimensions. It seems highly probable, there- 
fore, that the combined pressure and heat of the superincumbent 
trachytes should have been instrumental in causing the extensive 
system of fissuring now observed more particularly in the lime- 
stone walls. Wherever cracks thus formed were in connection 
with the original ore-bed, they would have been filled from the 
latter, by some process, probably, which could derive material 
aid from the presence of heated masses overlying. One hypoth- 
esis of this kind might also account for the high average grade 
of ore found in the transverse veins as compared with the main 
ore-body. 
The treatment of ores from the districts above described has. 
met with no obstacle thus far. By milling process the lower 
grades can be utilized, while smelting is advisable for the higher. 
For a long time the Mexicans have smelted a limited quantity of 
certain classes of ore. They are, no doubt, very skillful in man- 
ipulating ores with which they are familiar, but their crude 
methods and their conservatism, born of constitutional laziness, 
Prevent their harvesting the riches of the country they inhabit. 
It is Surprising, sometimes, to see the results obtained by them in 
their small adobe furnaces. Capable of smelting perhaps 500 
pounds of ore a day, the construction closely resembles that of 
an ordinary silver-lead furnace. By means of cupellation, all 
blast being supplied by hand-power bellows, they produce silver 
of 930 fineness. Their entire plant seems almost like a play- 
thing, but it is constructed upon sound principles and handled 
with enviable skill. Until the arrival of Eastern machinery these 
miniature smelters afforded the only means of extracting the pre- 
cious metals from their ores. Now they have had their day, and 
are rapidly falling into disuse. 
r $ K 
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