E 302 3 
SECT. XXXVL 
Moft part of the lead ores may be broi^glit td a 
metallic lead upon the charcoal The Miners plumhi 
€alciformes^ which are pure, are eafily melted into 
lead : but fuch of themj as are mixed with an ochra-* 
ferric or any kind of earth, as Clay, Lime, &c. 
yield very little of lead^ and even nothing at all^ 
jf the heterogenea are combined therewith in any 
large quantity : this happens even with the Minera 
plumhi calciformis arfenico mixta, Thefe, therefore, 
are not to be tried but in larger laboratories. 
However, every mineral body fufpeded to contain 
any metallic fubftance, may be tried by the blow-^ 
pipe, fo as to give fufficient proofs, whether ir 
contains or not, by its effedls being different from 
thofe of the ftone or earths, &c. 
SECT. XXXVII. 
The Miner a plumhi miner ali f at leave the 
lead in a metallic form, if not too large a quantity 
of iron is mixed with it. For example, when a 
teflellated or fteel-grained lead ore is expofed to 
the flame, its fulphur, and even the arfenic, if 
there be any, begins to fume, and the ore itfelf 
immediately to melt into a globular form ^ the reft 
of the fulphur continues then to fly off, if thd 
flame is blown flowly upon the mafs, inflead of 
that, very little of the fulphur will go off, if the 
flame is forced violently on it : in this cafe, it ra- 
ther happens that the lead itfelf crackles and dilTi- 
pates, throwing about very minute metallic par-^ 
tides. The fulphur being driven out, as much as 
pofTible, which is known by finding no fulphureous 
vapour in fmelling at the proof, the whole is fuf- 
fered 
