C. T. Jackson on Crystals of Galena. 405 
ART. XXXI— CHEMICAL AND MINERALOGICAL FRAGMENTS. 
By C. T. Jacksos, M. D. 
Remarks on the Formation of Crystals of Argentiferous 
Galena, by Sublimation. 
Ar the meetings of the American Association of Geologists 
and Naturalists in Boston, New Haven and New York, I pro- 
posed to account for the origin of several metalliferous veins, 
by sublimation of their ores or constituents. In favor of this 
theory, I mentioned that a considerable loss was sustained in 
smelting lead ores, owing to the evaporation of the sulpburet 
of lead at the temperature required for its reduction ; and 
called the attention of geologists to the quantities of sulphuret 
of lead which rise in the chimneys of smelting works, and to 
the particles of sulphuret of lead which fall on the roofs of 
the buildings, and on the surrounding soil. 
It was ascertained by Berthier, that when galena is kept 
fused in a crucible, lined with charcoal, in which the reduction 
of the lead could not take place, a considerable portion of the 
galena was actually lost by sublimation. It is also known, 
that although silver is regarded as fixed in the fire, and does 
hot volatilize when exposed for weeks to the heat of a porce- 
hin furnace, it is partially sublimed with the vapor of lead in 
the Process of cupellation ; and that the last portions of litharge 
lown Over, contain a notable proportion of silver. 
: lt appears probable, that argentiferous galena is also vola- 
tile under certain circumstances ; and from some phenomena 
Which I observed at the Shelburne mines, and in the crystals 
af lead ore which I have examined, it would seem that the 
origin of those veins and crystals can be demonstrated to have 
risen from vapor of the ore. 
A cavern was struck by the miners, at the depth of about 
twenty feet, and the walls of this crevice were found to be 
Covered with crystals of argentiferous galena, associated with 
