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10 . HISTOKY OF CHEMISTRY. 



that ammonia formed an amalgam with mercury, was templed to assign 

 to it a metallic basis. But then he again hesitates, 6 and doubts whether 

 the analogies of our knowledge are not better preserved by supposing 

 that ammonia, as a compound of hydrogen and another principle, is 

 " a type of the composition of the metals." 



Our history, which is the history of what we know, has little to do 

 with such conjectures. There are, however, some not unimportant 

 principles which bear upon them, and which, as they are usually em- 

 ployed, belong to the science which next comes under our review, 

 Mineralogy. 



*Elem. Chem. Phil. 1812, p. 481. 



