mineralogy, not to supply their place, and therefore it is pre- 

 sumed, that in consulting the former he will always bring with 

 him some previous knowledge of the subject, at least, as regards 

 vocabulary and manipulation, as he is not to expect, in the pres- 

 ent attempt, any explanation of either of these necessary ad- 

 juncts ; in making which, however, the Compiler has endeavored 

 to render this preliminary knowledge a minimum, by giving 

 prominency only to the most obvious characters. F. H. B. 



EXPLANATION OF THE PLAN OF ARRANGEMENT. 



First Grand Division. 



It is the character of many of the metalhc minerals to hold, 

 among their constituents, volatile bodies, which, exposed to a 

 certain temperature, within the reach of the blowpipe, pass 

 off under the form of a vapor, usually both visible and odorif- 

 erous ; often condensing upon the support, (charcoal,) as a yel- 

 lowish, brownish, reddish, bluish or whitish powder. This is so 

 constant a characteristic of several metallic minerals, and at 

 the same time one so obvious to the senses, that its develop- 

 ment or non-development, under the action of the blowpipe, 

 may be well made portions of the grand frontiers of introduc- 

 tion and exclusion among them ; and accordingly, while volatil- 

 ity, with fusibility, or perfect volatihty alone, is made to limit the 

 first grand division, the want of volatility, with fusibility, limits 

 the second. 



The first grand division is separated into two divisions, the 

 distinguishing feature of which is still one of volatility, viz. the 

 development, or not, of an arsenical odor before the blowpipe.* 



* The blowpipe has sometimes been described as a difficult instrument to use ; 

 whereas, for all common purposes of roasting and reduction, it is very easy. The 

 directions which are usually given, to contract and distend alternately the muscles 

 of the face, at the same time breathing through the nose, are unnecessary and oc- 

 casion a number of useless grimaces. If so unexperienced a practitioner might pre- 

 sume to give a word of advice, it would be, to persevere in blowing steadily and 

 moderately, with the endeavor always to preserve, as long as possible, a well de- 

 fined flame, a cone within a cone, the innermost being blue : repeat this a few times 

 and the rest will soon follow. 



