68 MINER A LOGICAL 
Thefe experiments prove at the fame 
time that a portion of iron is not inju¬ 
rious to the preparation of fmalt, if the 
cobalt is free from other fubftances. 
.. / 
The fuppofed Tungften from Cornwall. 
§ 
The true tungften, or lapis pondero- 
fus, which now begins to be fo very 
fcarce, is known by its being fufible, by 
a proper addition of microcofmic fait, 
with the blow-pipe, and making a clear 
blue glafs, but ft ill more certainly by its 
afluming a yellow colour when pow¬ 
dered, and digefted with nitrous or ma¬ 
rine acid. 
Another, not lefs fure way, to diftin- 
guifti true tungften from ponderous fpar, 
quartz, and other ftones, is by the hy- 
droftatical balance. The fpecific gravity 
of tungften in pure, compad, white 
pieces. 
