1872.] Capt. W. A. Ross on Pyrology, or Fire Analysis. 



471 



slight sublimates, the steellegsof the forceps should be polished bright before 

 use, and then pointed downwards near a window, when the slightest deposit 

 will affect the appearance of the shining surface through a lens. 



87. The distinction made by writers on the "blowpipe" between subli- 

 mates of metals by means of the different distances at which they are de- 

 posited from the assay on charcoal, is apparently based on an error, as these 

 seem to be due chiefly to the violence or weakness, as the case may be, of 

 the superposed blast (paragraph 7). This may be proved by causing the 

 sublimate of the same metal, as antimony, to be deposited at different dis- 

 tances, as shown in fig. 8 at c c c, through modified blowing. 



88. The same figure shows the manner in which it is proposed to utilize 

 the whole effects of the hydrocarbonous pyrocone for sub- ^„ g t 



stances which cannot be conveniently supported on platinum 

 wire, as metals or alloys, by which the defects of large pieces 

 of charcoal in breaking up and spreading out the pyrocone, 

 and in absorbing and wasting so large an amount of heat, may 

 be avoided. This is by sawing charcoal paste (made of C 

 powder, flour, and water according to the directions given in 

 Plattner's work) into parallelograms about lj inch long by 

 a \ inch deep, and bevelling or slanting off one end as at b. 

 This is called a "charcoal mortar," and is supported by a 

 common sewing-needle stuck into one side, as at «, figs. 8 and 

 10. A cavity is scooped at first in the slanting face of the 

 mortar with the point of a penknife, or, better, an implement 

 like fig. 9, which is the representation of a broken drift. After 



some use the mortar burns away as shown in fig. 10; but no fresh cavity 



Fig. 10. 



requires to be scooped, as the assay being hotter than the surrounding 

 paste, burns a place for itself, while the great advantage is obtained by 



