A SYSTEM OF 
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this work ; they are here only defcribed, fuch as 
they are naturally found, viz- entangled in certain 
heterogeneous bodies, of which they require but 
very little for their faturation. 
SECT. CXLIV. 
The THIRD CLASS. 
MINERAL INFLAMMABLE SUBSTANCES, 
Phlogifia Mineralia, 
To this clafs belong all thofe fubterraneous bo- 
dies that are diffoluble in oils, but not in water, 
which they repelj catch flame in the fire; and are 
electrical. 
It is difficult to determine what conftitutes the 
difference between the purer forts of this clafs, 
fmce they all muff be tried by fire, in which they 
all yield the fame produCt; but thofe which in 
the fire fliew their differences by containing diffe- 
rent fubftances, are here confidered as being mixed 
with heterogeneous bodies : that fmall quantity of 
earthy fubflance, which all phlogifta leave behind 
in the fire, is, however, not attended to, 
SECT. CXLV. 
I. Amber grife, Amir a grifea- 
Is commonly reckoned to belong to the mi- 
neral kingdom, although it is faid to have doubt- 
ful marks of its origin. 
d. It has an agreeable fmell, chiefly when 
burnt. 
h. It is confuted in an open fire* ^ ' 
c. It 
