[ 6 4 ° ] 
with mercury, in order to extract the gold, of which 
poffibly it at ffiff: contain’d a conliderable quantity. 
The quantity left by the workmen is extremely fmall ; 
fome pounds of the mixt having yielded only a few 
grains. A moderate fire renders more of thele golden 
particles difcoverable, than can be feen at firft j the 
mercury evaporating, by which feveral of them were 
concealed. 
2 . Some part of the brownifh powder is probably 
adventitious, as well as the mercury ; being worn off 
from the {tampers and mills employ’d for commi- 
nuting the mineral, and triturating it with the mer- 
cury. 
3. The roughnefs and dark colour of the cavities 
of the grains of platina feem to proceed from a fub- 
ffance fimilar to the black duft, adhering in them. It 
is probably owing likewife to this heterogeneous mag- 
netic matter, that fome of them are attracted by the 
loadflone. 
Experiment 2. 
Some of the purer grains of platina, by gentle 
ffrokes of a flat hammer, upon a fmooth anvil, bore 
to be confiderably flatten’d, without breaking or crack- 
ing about the edges : fome quickly crack’d, and dif- 
cover’d internally a clofe granulated texture. All are 
reducible, by rude ftrokes in an iron mortar, tho’ with 
difficulty, into powder. They feem’d to be rather 
more brittle when ignited, than when cold. 
Experiment 3. 
The fpecific gravity of platina, with its hetero- 
geneous admixtures, as brought to us, was found to 
be 
