140 The Principles of Part III. 



matrix to extract the acid from the air ; 

 and by keeping the matrix open to admit 

 the air, by a continual fermentation carried 

 on in the body expofed. 



TH E third opinion, which almoft all 

 chymifts follow, is, That the alkaline vola- 

 tile falts, produced by the fermentation of 

 corrupted bodies, animal or vegetable, and 

 the abforbent terreftrial particles, which 

 are ufed as the matrix to make nitre, at- 

 tract from the air, which is plentifully 

 ftored with it, the acidum vagu/n, or vi- 

 triolic acid j which joining with the oil of 

 the matrix, flored with it, becomes the 

 acid of nitre. This univerfal acid, Hom- 

 lerg makes the origin of the nitrous and 

 {he marine acid : for, added to an inflam- 

 mable matter, it becomes the nitrous acid ; 

 to an arfenical matter, it becomes the 

 marine acid. The arguments ufed in fa- 

 vour of this opinion are, i . That putrefied 

 animal fubftances are employed in the for- 

 mation of nitre, and, therefore, the oil 



mull: 



