DOMAIN XI. DECOMPOSED. 211 



clay, which forms so prodigious and import- 

 ant a portion of the surface of this globe, 

 and furnishes aliment to animals and ve- 

 getables, arises from a decomposition ef- 

 fected, during myriads of ages, by the 

 superincumbent waters ; or by a mere de- 

 position from the original mass and consti- 

 tution of the waters themselves. 



On the decomposition of rocks, the ob- 

 servations of a skilful chemist must be 

 particular] y exact and interesting, for which 

 reason those of Mr. Kir wan are extracted ; 

 more especially as they abound with ex- 

 amples which are essential to the nature of 

 the present work. It may also be pre- 

 faced, that the decomposed rocks have 

 never hitherto been treated in any profess- 

 ed work of mineralogy, so that the riovelty 

 of the subject calls for every aid of illus- 

 tration. 



" Decomposition consists in the separa- Kirwan's 



explanation, 



tion of the constituent parts of a stone, or 

 other substance ; and may be either total 

 or partial. Disintegration denotes the se- 



p 2 



