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xxxviii INTRODUCTION. which firfl attracts our notice, and placing theothersin their correfponding places, viz. figure, luflre, fradture, fragments, didindt concretions, frangibility, brittle- nefs and weight e. That they Jhoukl be fvffcicnily accurately de termined. Many minerals are completely alike, ex cepting in certain fhades of character, which mud alfo be mentioned if we do not wifh to be deprived of the didirndions they afford. Thus it is not enough in defciibing white filver ore, to fay that is has a grey colour, nor even that it poffeffes a lead grey colour ; accurate determination requires that the colour of white filver ore fhould be given—fallow lead grey. 7. That it fhould contain only j'uch cxpreffions as have met with umverfal approbation. g. That the degree of the frequency cf the occur rence of any one of thefe charafters Jhould be expref fedy as by the following terms, abundantly, com monly, fornetimes, partly, feldcm, rarely, very rarely. h. That the defcription fmdd be written fa as to afford a fynoptical view, and that tire char afters may eqfily attract the eye. This is bed done by be ginning each character by a new line, and diftin- guifhing the mod important ones by capital letters, or, by printing in italics. My knowledge of oryao- gnofie is too limited to permit me the ufe of italics. Wenwr s In defcribing a mineral, according to the method incthod of r , TT i i „ iicicribinjr of Werner, we do not employ a few ifolated charac- -ajmera). ag j s j n Z00 < 0 gy an J g otanyj a$ { j UV( , already mentioned, a feries or fuite, which being pe culiar to the fpecics, confequently chara&tfifcs it. But