Happen. The fiiver is then found inclofed in thzr 

 ilag of a globular form, and quite mining, as if ic 

 were polifhed. When a large quantity of fiiver is 

 contained in a lead ore, viz. in a potter's ore, i& 

 can like wile be difcovered through the ufe of the: 

 blowpipe, of which more will be mentioned here- 

 after. (Sect- xxxix.) 



SECT. XXXV. 



Of the pure Tin ores, the tin may be melted " 

 out in its metallic flare. Some of thefe ores melt. 

 very eafily, and yield thtrir metal in quantity, if 

 only expofed to the fire by themfelves : but others 

 are more refractory, and as thefe melt very (lowly,, 

 the tin, which fweats out in form of wry fmall glo- 

 bules, is inflantly burnt to aihes, before thefe glo- 

 bules have time to unite, in order to compofe a 

 larger globe, which might be fee n by the eye, and 

 is- not ib foon deitroyed by the fire > it is therefore 

 necefTary to add a little borax to thefe from the 

 beginning, and then to blow the flame violently 

 at the proof. The borax does here preferve the 

 metal from being too foon calcined, and even con- 

 tributes to the readier collecting of the fmall me- 

 tallic particles, which foon are feen to form them- 

 felves into a globule of metallic tin at the bottom 

 of the whole mafs, neareft to the charcoal. As 

 foon as fo mych of metallic tin is produced, as is 

 rufricient to convince the operator of its prefence, 

 the fire ought to be ce&kd; although not the whole 

 of the ore is yet rnplted j becaufe feldom, or ra- 

 ther never, the whole of this kind of ore can be 

 reduced into metal by means of thefe experiments,, 

 a great deal thereof always being calcined : and if 

 the fire is continued too long, perhaps even the 

 metal, already reduced, may likcw;fe be burnt- to 

 afnes : for the tin is very foon deftroyed from its 



cttllic ftatt by the fire/ S 'E C T. 



