COMBUSTION. 143 



in appearance. Its size is diminished, while its length is 

 increased, and its brightness almost entirely destroyed, ow- 

 ing to the more perfect combustion of the carbon within it. 

 The three cones named in 172 are still seen, the inner one 

 is of a blue color, the middle one is partly luminous, and 

 the outer one is again paler. The middle cone is called the 

 deoxidizing or reducing flame, and has the effect of reduc- 

 in<^ metallic oxides brought under its influence. This is 



O O 



owin<* to the fact that it contains an excess of combustible 



O 



matter, and is ready to take oxygen from the metals. The 

 outermost cone, called the oxidizing flame, has the opposite 

 effect, for the supply of oxygen is here abundant, and any 

 substance eager to take it up is oxidized. The hottest part 

 of the flame is a little beyond the end of the middle cone. 



In skillful hands either the reducing or the oxidizing 

 flame may be made to predominate, and advantage is taken 

 of this by the operator according as he may desire to reduce 

 or oxidize any substance. This little instrument is of great 

 service to the chemist and mineralogist to assist them in as- 

 certaining the nature of mineral substances. The material 

 to be examined is supported on charcoal, or in platinum- 

 pointed pincers, and heated in the blow-pipe flame ; by the 

 changes which take place in its appearance the chemist is 

 able to determine its constituents with considerable accu- 

 racy. 



183. Improper Management at Fires. The principles 

 above indicated are often disregarded in attempts to put 

 out fires. The more we can keep the air from having free 

 access to a fire, the more readily shall we put it out. If a 

 fire, then, be on the inside of a building, there should be no 

 more openings made into it than are absolutely necessary 

 to enable us to throw water upon the fire. Especially 

 should we avoid making any openings which will allow a 

 current of air to pass through the part that is burning. If, 



