Chap. 9.], Flint, 51 



called liquor of flints. This earth is perfectly dif- 

 folved in that wonderful boiling water-fpout, above 

 fixty feet high, at Geyfer in Iceland, where by cooling 

 it forms a hard filiceous mais. Pure filiceous earth is 

 obtained by fufirig * clear quartz with four times its 

 weight of fixed alkali, diffolving the whole in diftilled 

 water, and precipitating the earth by an acid. Its 

 fpccific gravity is 2,650. 



M. Bergman has formed perfect filiceous cryftals 

 by diffolving filiceous earth in the fparry acid, and 

 iuffering it to cryftallize flowly. It is probable that 

 nature forms them in a long courfe of time from a 

 folution or diffufion of this earth in water. 



Of the newly difcovered earths I fliall treat in a fe- 

 parate chapter, though it may be premifed, that they 

 are rathtr of importance in order to complete the no- 

 menclature of the mineral kingdom, than from their 

 quantity or their properties. 



Though the fimple earths are all infufible alone, yet 

 they may readily be fufed by mixture with each other. 

 The calcareous earth is found to 06t as a menftruum 

 in diffolving the other earths by heat j and when it has 

 once afted on any earth, a compound menftruum is 

 formed, which afts ftill more efficacioufly in diffolving 

 other earths. Hence it is, that any three of the fimple 

 earths may be fufed into glafs, provided calcareous 

 earth is one- of the number. 



Thus far it appeared neceffary to premife concern- 

 ing the general properties of the fimple earths in their 

 feparate ftate j but as their combinations are various, 

 and their ufes in this laft ftate very important, it will 

 be proper to treat of each on a more ample fcale than 

 the limits of a fingle chapter would admit. 



* Melting by heat. 

 E 2 



