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* viii PREFACE. Wallerius, in the new edition of his Syftema jVIineralogicum, publiflied at Stockholm in 1772, was the firft who fubjeded to a ferious examina tion the principles on which mineralogifts had hi therto arranged minerals. He rejeded the cha racters drawn from ufe, value, and geognoftic fituation, and affirmed, that claffes, orders, and ge nera Ihould be arranged according to chemical, but fpecies principally in conformity with the external charaders. Thefe principles he employed in the conftrudion of his fyftem, which proved the moll complete, and poffefied the moll determinate nomen clature of any that had hitherto appeared. By thug combining with the chemical charaders thofe exter nal charaders that were then known, he enabled mi neralogifts to difcriminate minerals with more cer tainty than they had been hitherto able to do. Still, however, the want of a proper mineralogical language rendered all fyftems and defcriptions impeded, and comparatively ufelefs. The external charaders em ployed by Agricola, Linnaeus, Wallerius, Hill, and others were either undefined, or fo inaccurately ex plained that it was difficult to underftand, or avoid confounding them with one another ; befides, they were employed irregularly, and even frequently in termixed with chemical, phyfical, and empyrical cha raders'. The illuftrious Werner early faw the impoffibility of mineralogy advancing fteadily without a determi- * Hill’s foflils, arranged according to their various obvious charaders, Londoti, 1771, 8vo. nate