[ 68 4 ] 
rifled in aflay-crucibles, by intenfe fires, in a blatt 
furnace, and blown off on tetts before the nofe of a 
bellows, with the fame event ; the platina not only 
perfectly refitting the power of lead, which by thefe 
operations deftroys every other known metallic body, 
except gold and filver, but likewife retaining and 
preventing the fcorification of a part of the lead it- 
felf. 
3. In the hiftory of the fufion of platina with 
lead, it has been obferved, that this metal depofites 
in a gentle heat great part of the platina, which had 
been united with it by a ttrong one. As the part, 
which remained fufpended, might be prefumed to 
differ from that, which fubfided , a quantity of lead 
was decanted off from frefh parcels of platina, and 
both the decanted metal and the refiduum fubmitted 
to the preceding operations feparately. The event 
was ftill the fame j the matter becoming confiftent, 
when the lead had been worked off to a certain 
point, and refufing farther fcorification. 
4. A mixture of platina and lead, which had 
been cupelled- in an affay-furnace as long as it could 
be kept fluid, was expofed in a crucible to a fire ve- 
hemently excited, by itfelf, with powdered charcoal, 
with black flux, borax, nitre, common fait. The 
matter neither melted, or buffered any confiderable 
alteration, becoming only fomewhat more porous j 
probably from a little of the lead having exfuded 
without the liquefaction of the mafs. The imme- 
diate contact of burning fuel, agitated by bellows, 
made fome of thefe mixtures flow, after they had 
refufed to melt in veffels acted upon by intenfe fires. 
Very little of the lead was diflipated by this means. 
f. Upon 
