On the Generation of Statical Electricity. 93 
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which makes, with the ferruginous trap rock, a perfectly liquid 
glass or slag, through which the metallic alloy of copper and 
silver quickly settles. The proportion of silver in the metal, re- 
duced in the furnace, varies from 5 to 16 per cent. according to 
the nature of the ore. The average yield of the rock when as- 
sayed in the crucible with limestone and charcoal, is 7,4; per cent. 
of metal; and the metal analyzed yielded 94-864 per cent. of 
copper, and 5:136’per cent. of silver. The silver being worth 
’ $102 50, and the copper $15 17 = $117 67 for 100 lbs. of metal. 
In the furnace operations there may be a loss of copper by mis- 
management of the blast, or for want of skill in the workmen; 
but the silver, being incapable of oxidation in the fire, cannot be 
lost. By numerous experiments, we have ascertained that the 
best proportion of lime is about one third the weight of the ore, 
or if calc spar is used, about half the weight may answer. Even 
less than this would render the molten mass sufficiently liquid in 
a blast furnace, where the weight of the metal and the intensity 
of the heat render the assay much more easy than it is in cruci- 
bles. The cale spar of some of the localities on the Company’s 
lands, contains a considerable quantity of native copper, with a 
little of the carbonate. This should be preferred as a flux, for 
the copper it contains will be saved. 
The vein of datholite at Eagle Harbor will also make an ad- 
mirable flux, and the copper it contains will add to the yield of 
the furnace; while the borosilicate of iron and copper mixed 
with it, being saturated with oxide of copper, will not take up 
the metal in fluxing the ore. Ihave used it with advantage in 
some of my experiments, and find it to work perfectly well. 
Art. XI.—Practical Observations on the Generation of Stat- 
ical Electricity by the E'lectrical Machine; by Lieut. GeorcE 
W. Rains, U.S. A., Acting Assistant Prof. of Chem., Min. and 
Geol., U. S. Military Academy. 
Havine experienced, at different times, some difficulty in caus- 
ing an abundant and uniform supply of electricity to be generated, 
by the apparatus employed, when the state of the air and other 
circumstances appeared entirely favorable, sufficient inducement 
was offered to devote a few leisure moments to the study of the 
causes of failure. 
