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A SYSTEM OF 
lithographifts entirely omitted, and by others 
ranked among the iron ores *, but, as I am con- 
vinced both by my own experience, and by that 
of others, that they contain no greater quantity 
of metal than fometimes two or three per cent, 
of iron, and fometimes a little tin, I think that 
the remaining part, which muft confequently be 
confidered as a kind of earth, deferves its parti- 
cular feparate place in a mineral fyftem, at leaft 
until a farther infight into its nature may b^ ob- 
tained: and to this opinion I have been per- 
fuaded by its following peculiar qualities : 
1. The manganefes confift of a fubftance, which 
gives a colour both to flags, and to the folu- 
tions of falts, or, which is the fame thing, 
both to dry and to liquid menftrua ; viz. 
a. Borax, which has diflfolved manganefe in 
the fire, becomes tranfparent, of a reddifh 
brown or jacinth colour. 
i>. The microcofmic fait becomes tranfparent 
with it, of a crimfon colour, and moulders 
in the air. 
<r. With the fixed alcali, in compofitions of 
glafs, it becom.es violet ; but if a great 
quantity of manganefe is added, the giafs 
is in thick lumps, and looks black. 
J. Scorified with lead, the glafs gets a red- 
difh brown colour. 
e. The lixivium of a deflagrated manganefe 
is of a deep red colour. 
2. It deflagrates with nitre, which is a proof 
that it contains fome phlogifton. 
3. When reckoned to be light, it weighs 
as much as an iron ore of the fame tex- 
ture. 
4. Being melted together with glafs compofi- 
tions, it ferments during the folution : but 
it 
