Chemical Apparatus. 12 1 



flame increases the heat must be obvious. Flame 

 is ignited vapour, and by being agitated, a greater 

 surface of inflammable vapour is exposed to the 

 contact of the atmospherical air, and in that 

 situation which is favourable to the combination 

 of the oxygen of the air with the inflammable 

 matter, which is therefore condensed, and the 

 caloric it contained is set free. To illustrate this 

 by the blow-pipe, which is a tube of glass or 

 metal bent, it will be more convenient if there is 

 a globe blown at the angle of the pipe to con- 

 dense the moisture of the breath. By this we 

 find a flame of a very moderate size, when agi- 

 tated with air, produces a v^ry intense heat. 

 This instrument is often useful in adjusting small 

 vessels, or in sealing them up, or in trying a 

 mineral by exposing it on a piece of charcoal to 

 the heat produced by it. There is some art in 

 managing the blow-pipe so as to produce a con- 

 tinued stream of air. This is effected by apply- 

 ing the tongue to the roof of the mouth in such 

 a manner as to interrupt the communication be- 

 tween the mouth and the nostrils. By these 

 means the operator is enabled to breathe through 

 the nostrils without varying the blast through 

 the pipe. A wax candle with a thick wick is 

 very convenient for experiments with the blow- 

 pipe ; but a good tallow candle will answer most 

 purposes. The body to be acted upon should 

 seldom exceed a pepper-corn in size. Consider- 



VOL. II. G 



