t 301 I 
liappen. The filver is then found inclofed in tfie 
flag of a globular form, and quite fhining, as if k 
were polilhed. When a large quantity of filver is 
contained an a lead ore, viz. in a potter’s ore,, k 
can likewife be difcovered through the ufe of the 
blowpipe, of which more will be mentioned here^ 
after., (Sed:., xxxix.) 
SECT. XXXV. 
Of the pure Tin ores, the tin may be melted 
©ut in its metallic flate. Some of thefe ores melt 
very eafily, and yield their metal in quantity, if 
dnly expofed to the fire by themfelves : but others 
are more refradory, and as thefe melt very flowiy,* 
the tin, which fweats out in form of very fnlall- glo- 
bules, is inftantly burnt to afhes, before thefe glo- 
bules have time to unite, in order to compofe a; 
larger globe, which might be feen by the eye, and 
is not fo foon deilroyed by the fire ^ it is therefore 
neceffary to add a little borax to thefe from the 
beginning, and then to blow the flame violently 
at the proof. The borax does here preferve the 
metal from being too foon calcined, and even con- 
tributes to the readier colieding of the fmall me« 
tallic particles,, which foon are feen to form them- 
felves into a globule of metallic tin at the bottom 
of the whole mais, nearefl: to the charcoal. As’ 
foon as fo much of metallic tin is produced, as is 
fufficient to convince the operator of its prefence, 
the fire ought to be ceafed, although not the whole 
of the ore is yet melted*, becauie feldom, or fa- 
ther never, the whole of this kind of ore can be 
reduced into metal by means of thefe experiments, 
a great deal thereof always being calcined : and if 
the fire is continued too long, perhaps even the 
metal, already reduced, may likewife be burnt to 
afhea : for the tin is very foon deftroyed from. its 
metallic ftate by the fire. S E CTh 
