mineralogy. 
r^dfdns for this fuppofition. The generation df 
fulphur and marcafite requires no preferable phlo-^ 
gillon out of any of the kingdoms of Nature, for 
the phlogiftons throughout all nature are equally 
alike fit for it. 
It is a fublime fubje6t for pliilofophers to en« 
quire how far fire, phlogifton, and eledricity, have 
an affinity with, or dependance on, one another-, 
but as they yet want that light in this matter 
which they wiffi to have, I hope to be excufed for 
not mentioning any theories on the fubject. 
This clafs is of great ufe in medicine ; for in- 
ftance, the ambergrife, the fait of the yellow am- 
ber, the rock-oil, the afphaltum, and the fulphur. 
The rock-oil and fulphur are ufed in fireworks, 
the afphaltum by the watchmakers, and the yellov/ 
amber is uftd by the varnilhers and painters 
SECT. CLXIIL 
The F O U R T H C L A S S. 
METALS, ME^ALLJ, 
Are thofe mineral bodies which, with relped 
to their volume, are the heavieft of all hitherto- 
kliown bodies they are not only malleable, but 
they may alfo be decompounded, and in a melt- 
ing heat be brought again to their former ftate. 
The coalsj however, are of the greatell coftfequence for 
their oeconomical ufe ; and happy therefore are Lhcie countries 
which have a fufncienc quantity of them, lince they may be 
employed as fuel to almod every purpoh, wliich is plainly 
proved in England-, E, 
M ,2 
by 
