26 THE PROSPECTOR'S HANDBOOK. 



(N.B. By heating a point of a straight tube in a spirit lamp, 

 the tube may be bent into the required angle.) The char- 

 coal on which the mineral is to be heated ought to be made 

 from very light wood such as elder, pine, &c. and which, 

 when heated, should be as free from smoke and ash as 

 possible. 



To treat the substance on charcoal, a small cavity should 

 be bored on the edge of the grain in the top part of the 

 charcoal by means of a knife-blade, and when the blowpipe 

 flame is directed on the specimen, the support should be 

 held in an inclined position, in order that the incrustation 

 deposited on the cool portion can be properly noticed. 



An aluminium plate about 4 inches long by 2 broad, and 

 ;n> inch thick, and with half an inch at the end bent nearly 



FIG. 22. 



at right angles to the other part, and on which the specimen 

 can be rested, is a capital support ; only, as the plate is apt 

 to become very hot during an operation, it must be held by 

 tongs, the handles of which are wadded, so as not to come 

 in contact with the operator. In using this support the 

 specimen may be placed on a thin piece of charcoal. The 

 incrustations on the aluminium plate are thicker than those 

 on the charcoal support, and they can easily be experi- 

 mented on by the blowpipe. When the operation is over, 

 the plate may be cleaned by rubbing it with fine bone ash, 

 by means of a piece of washleather. 



Firstly, treat the substance alone on charcoal, and notice 

 the effect of the oxidizing and then of the reducing flame on 

 it. After which, treatment with carbonate of soda, and after- 

 wards with borax and inicrocosinic salt, may be necessary. 



As, sometimes, metals cannot be reduced from minrnils 

 by simply heating on charcoal alone, carbonate of soda is 



