1 8 Elements of Mineralogy. 



divides the compound, as to render it more 

 foluble. Thus lime-ftone, and mild mag- 

 nefia, are more eafily diflblved than either 

 lime or calcined raagnefia. On the other 

 hand, fome metallic calces are more eafily 

 diflblved in certain acids, than they are when 

 furnifhed with phlogifton, though this alfo be 

 refolvable into an elaftic fluid ; but this I have 

 elfewhere explained. The calces of iron are 

 fo much the more difficultly diflblved, as they 

 are more dephlogifticated ; hence the whitifli 

 calx is moft difficultly diflblved; and next to 

 that the yellowifh and red ; but the brown, 

 green, and blue, moft eafily ; and hence, 

 ftones which contain dephlogifticated calces 

 of iron and unareated Earths, are moft diffi- 

 cultly diflblved, though the calces are not fo 

 ftrongly attracted by the Earths, nor confe- 

 quently the ftones fo hard, as thofe that con- 

 tain iron in a more phlogifticated ftate. This 

 accounts for the difficult folubility of talc, 

 mica, &c. 



CHAP. III. 



Of the Syjlematical Arrangement of Earths 

 and Stones. 



All Earths may be divided into fimple and 

 compound. Simple are the five unalterable 

 kinds already defcribed, which conftitute five 

 forts or genera* under which all terrene coni- 

 pounds may be ranged. 



By 



