OF FOSSILS. 



on), but al \vays united to A, or fome other mat- 

 ter, and ever inferior in weight in fuch combi- 

 nations. According to the rule propofed above, 

 the genus B fliould difappcar entirely, and be 

 altogether wanting in the genera of* its own 

 clafs, which is by no means confident with a 

 , natural lyiU-m. 



Again, let us fuppofc B excels A in the in- 

 teniity of its properties, fo that B is only equal 



A 

 in weight to , yet notwithftanding the quali- 



N 



tics of B arc clearly predominant in the compo- 

 iition A B, tliat is, arc much more confpicuous 

 than thole of the lefs ingredient A. Here again, 

 unlcfs I am deceived, we are to admit another 

 exception. 



If the cafes propofed under B and C obtain at 

 the fame time, the exception receives a double 

 confirmation. 



Sometimes it feems ncccffary to give a prefe- 

 rence to the price of particular fubflanccs. Sup-' 

 pofc ABC an ore, whofc metal C, though of 

 lefs weight than any other part of the mixture, 

 yet in value furpafles both B and A, fo that they 

 arc entirely negledcd, and C only thought wor- 

 thy the expence of mctallurgic operations. In 

 this cafe A B C is in fad the ore of C ; but if 

 the proportion of quantity were regarded, it 

 fhould belong to the genus of A, and with great 

 propriety, if a natural fyftcm only is required. 



We 



