42 MINERAL© GICAL 
three-fourths of a grain in weight. Of 
this examined with the blow-pipe a part 
rofe in arfenical fmoke, and left one-eighth 
of a grain of iron attractable by the magnet. 
To half of the folution in marine acid 
was added phlogi dated alkali 5 by which 
the calx of tin was precipitated of a white 
colour with fome fpots of blue. From the 
other half, faturated with volatile caultic 
alkali, the tin was precipitated likewife 
an form of white calx: after Handing 
for fome time a fmall cloud of yellow 
calx of iron hung over it. 
*c 
SULPHURATED TIN-ORE. 
In thofe pieces I have examined, which 
were indeed of the fame vein, but taken 
from different parts of it, I found, ac¬ 
cording to the difference of colour and 
iplendor, the proportion of the compo¬ 
nent parts fomething different. To that 
the fureft way of afcertaining the true 
proportion 
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