156 NATURE STUDY 



of flame. The center is unscorched and may be blackened. This 

 is where the dark central portion of the flame was in contact with 

 the paper. If a splinter of wood is held across the flame a short 

 time, it will be scorched where the outer coats touch it, but un- 

 scorched where the central portion meets it. 



A very small glass tube three or four inches long may be 

 thrust into the central portion and the outer end inclined upward. 

 In this position it will tap the central portion, when smoke will 

 issue from the tube. This may be lighted, and thus give us a 

 a new small flame, showing that the central portion is composed 

 of combustible gases, 



The blue cup at the bottom is just in the position where the 

 ascending currents of air strike it to the best advantage, and 

 insures good combustion without smoke and floating particles of 

 carbon. This gives great heat, but little light. 



The air reaches the two outer coats of the flame, and com- 

 bustion takes place in them. In the one next the dark center 

 the carbon particles, as has been said, are passing thru and 

 glow with a bright light. They are completely burned in the 

 outer coat. 



That particles of carbon may make a colorless flame bright 

 may be shown by sprinkling lamp black or powdered charcoal into 

 an alcohol flame. On the other hand, if with a glass tube drawn 

 out to a fine point, or with a blow pipe, air is blown well into a 

 candle flame, the whole of the flame will become blue, no longer 

 giving out much light. 



A better supply of air makes a more prompt combustion of 

 all gases and carbon, but with the result of less illumination. 



If the supply of air to the candle flame is interfered with, the 

 flame smokes, much of the carbon and gases escaping unconsumed. 



The smoking lamp or the smoking fire means poor com- 

 bustion. In each case the smoke can be reduced by a better 

 supply of air. Questions may be proposed which will explain the 



