DOMAIN XI. DECOMPOSED. 



position, are water, oxygen, and fixed 

 air. 



" The internal causes are, the bases most 

 capable of forming a union with the exter- 

 nal : as saline substances, sulphur, slightly 

 oxygenated calces of iron, or of manganese, 

 lime, argil, bitumen, carbon, and mephitic 

 air ; which is certainly contained in many 

 stony substances, as Dr. Priestly has shown 

 in the first volume of his last edition, p. 64 ; 

 but as to its nature and effects, they are at 

 present too little known ; all these are as- 

 sisted by a loose texture of the substance 

 acted upon. 



" Saline substances, particularly when salts. 

 (relatively to their mass) they present a 

 large surface, are dissolved by water, and 

 consequently the stones, of which they 

 sometimes form a component part, are de- 

 composed ; thus muriacite, which consists 

 of 27 per cent gypsum, 14 common salt, 5 

 mild calx, and 53 micaceous sand, must be 

 decomposed when long subject to the ac- 

 tion of water. 



" Sulphur promotes decomposition by 



