i&2 A SYSTEM OF 



lithographifls entirely omitted, and by others 

 ranked among the iron ores ; bur, 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 coniequently be 

 confidered a.s a kind of earth, deferves its parti- 

 cular feparate place in a mineral fyftem, at leaft 

 until a farther infight into its nature mav be ob- 

 tained : i and to this opinion I have been per- 

 fuaded by its following peculiar qualities : 



i . 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 diflblved manganefe in 

 the fire, becomes tranfparent, of a reddifh 

 brown or jacinth colour. 



b. The microcofmic fait becomes tranfparent 

 with it, of a crimfon colour, and moulders 

 in the air. 



c. "With the fixed alcali, in compofltions of 

 glafs, it becomes violet ; but if a great 

 quantity of manganefe is added, the glafs 

 is in thick lumps, and looks black. 



d. 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 phlogiflon. 



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 3 it ferments during the folution : but 



it 



