230 ON A NATURAL SYSTEM 



fed of heterogeneous fubftances, mechanically 

 mixed, and united in aviltble manner, and which, 

 for the mod part, conltirute the entire fummits 

 of mountains, are comprehended under one 

 name of Petite or Saxn. Cronlledt has, with 

 great propriety, treated theft fcparately in an 

 appendix. The knowledge of thefe fubftances 

 is doubtlcfs highly neceliary, and tends much 

 to the illustration of phyiical geography ; but 

 they are not therefore to bo confounded with 

 bodies more homogeneous, whole combination 

 veiling on chemical principle*, is dlcclcd in the 

 way of folution. 



LXI. Organic FoJJlls. 



ORGANIC foflils are conlidered by Cronftedt 

 in another appendix. Thcfe fubltances are to 

 be treated as tlrangers from the animal or vege- 

 table kingdom. '1 hey arc diftinguiflied by an 

 organic llructure, more or It-is imperfect; of 

 which, as long as they bear any marks, we arc 

 to reckon them as follils of a foreign fpccks. 

 The confideration of them is however in various 

 points of view, highly ufeful. They refemblc u 

 fcrics of ancient coins in the teilimony they 

 bear to the convuliions and revolutions of our 

 globe, on which hillorical monuments are whol- 

 ly iilent. From them we may learn the wide 

 extended fovercignty of the fea ; the changes 



that 



