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Earths and Stones. *5 arife; and doubts may remain, which can be removed only by the application of Chemical tefts or internal charadters, not indeed analyfes, but other tefts of more eafy and fpeedy appli cation. Again, many minerals bave received their de- nominations merely from internal properties, fuch as limeftones and marls, &c. The only certain tefts ot thefe are chemical agents, though external charadters may afford a high degree of probabihty, ö b The over-zealous difciples of Mr. Werner contend for the fufficiency of external charadters, in all cafcs, with refpedt to ftonesthat have been already analyzed. 1t were an eafy, if not an invidious, talk to refute them, from the miftakes into which the moft eminent of them have fallen, through^ too great reliance on thefe charadters; but, in juftice to Mr. Werner, 1 muft fay, that u e rec °tntnends the aid of eafy chemical tefts, and has in fome cafes happily applied them. lt has been objedted to external charadters, by myfelf and many others, that they are not of a fixed and permanent nature, nor appropriated purely and lingly to any particular lpecies, but common to many, and incapable at leaft as to their gradations of a definition fufficiently precife. 1 he firft part of this objedtion is certainly true, if applied only to one or two of thofe charadlers; but, if they be takcn in their totality, it will very rarely happen that they fuit any mineral but one, and in luch cafes chemical tefts may decide; yet even this afliftance may be fometimes unfucctfs- ful, as in nature many fpecies border upon, and pafs into, each other, and thus der.y fufficient ßrounds of diftindfion. As to the difficulty arifing