314. Chemical Composition of the Brown Lead Ore. 
2. Botryoidal Brown Lead Ore of Mies.—It occurs at Mies, in Bo- 
hemia, in a gangue of clay slate with argentiferous Galena, Quartz and 
Brown Lead Ore of other varieties as respects form and color. The 
specimen employed in this examination forms botryoidal and globu- 
lar masses of the size of a pea. The globules were attached to Ga- 
lena, and exhibted within a liver-brown color, which passes into yel- 
low. ‘They were rough and sometimes crystalline upon their exte- 
rior,—always possessing a conchoidal fracture. The specific gravity 
of this variety was 6.444. Powdered crystals of it, heated with sul- 
phuric acid in a platina capsule, occasioned a very strong corrosion 
upon a glass plate held over the vessel. 
Heated before the blowpipe in platina forceps, the mineral melted, 
and crystallized on cooling. ‘The flame of the blowpipe was very 
perceptibly tinged green at its extremity. Fused with soda on 
charcoal, it afforded metallic lead and a brown slag. During this 
trial, 1 could perceive no odor of arsenic. ‘The solution of the 
mineral in nitric acid, from which the lead had been removed by 
means of sulphuretted hydrogen, afforded a dense cloud on the ad- 
dition of sulphuric acid mingled with alcohol, or of oxalate of potash ; 
whilst by repeating the passage of sulphuretted hydrogen through 
the same liquid, only a slightly yellowish precipitate made its appear- 
ance, which consisted of sulphur. Hence the entire absence of ar- 
senic acid was apparent. According to the mean of two analyses 
which were performed with three grammes of the mineral, I find its 
constituents to be, 
Oxide of lead, - - - - 75.830 
Muriatic acid, - - - = Qate 
Lime, - - -" - - 3-711) 
Phosphoric and fluoric acids, trace of iron and loss, 18.349 
100.000 
which gives the following composition : 
Chloride of lead, - - - 10.642 
Fluoride of calcium, ~ - - 0.248 
Basic phosphate of lead, - - 81.651 
saa lime, - - - 7.457 
99.998 
3. Crystallized Brown Lead Ore of Mies.—The specimen employ- 
ed in the following chemical examination, formed distinct prisms of 
