Volltext Seite (XML)
< *3 ) S E C T I O N III. Of the dißinßive Charafiers, and fyßematic Arrangement, of Eartfo and Stones. HThE objeft of mineralogy, at leaft in the fenfe in which that word is taken in this work, being •to point out the method of diftinguilhing the •various fubftances of which it treats, it is necef- fary at the outfet to give a general idea of the means it employs, to prove their fufficiency, and remove every ambiguity and obfcurity that may .attend their application. On the moft general •view of the fubjeft, it is plain thefe means can be no other than the properties of the fubftances themfelves, or at leaft fuch of them as are moft obvious, of moft eafy application, and at the fame time chara&eriftic of the fubftances to which they belong; v/e muft therefore examine what Jhofe properties are. The properties of fubftances, as far as we can underftand them, are the relations which they bear to our fenfes, and to other fubftances on or from which they are capable of producing or receiving fome peculiar obfervable change. Thefe Jaft-named fubftances are called chemical agents; fhe properties which relate to our fenfes are called the external, and thofe that relate to eher mical agents the internal, charaflers of bodies. In the Treatife I formerly compiled on this fübjeft I confidered the internal properties of minerals as the only that were fufficiently charac- teriftic of the fubftances to which they belonged. A fnpre tnature confideration has undeceived me. C ij. I per,