--3S- 



very same processes take place. The wood is heated, gases are given 

 off, which are burned on the spot. The flames of wood, coal, and oil 

 are gas flames. 



The Candle Flame. 



The special study of the candle flame will be best taken up some time 

 after the making of gas out of wood. The pupils are to find out that it 

 is a gas flame, the brilliant light being produced by minute particles of 

 carbon becoming incandescent as they pass from the center portion, 

 where no combustion is going on, through the part lying just outside 

 of this where the gases are in active combustion. The gases which 

 burn and the carbon which thus makes the light and is finally con- 

 sumed are all from the oil of the candle being decomposed into these 

 products by the heat, just as the same products are made out of coal by 

 heat in the process of the manufacture of illuminating gas, and in the 

 making gas out of wood in the experiments already given. None of 

 these facts are to be told at first, of course. 



By cutting up a few candles into short pieces each pupil can have his 

 own flame to study. 



Let each try to make out the parts of the flame. It will be found that 

 there are four: the blue cup at the bottom; a thin, almost transparent 

 outer sheet of flame; a brilliant light giving part just underneath this; 

 and a dark central portion. In the dark central portion is a mass of 

 gases charged with black floating particles of carbon (smoke). If a 

 sheet of paper held horizontally is suddenly thrust down on the flame 

 to about its middle and held for a short time, but removed just before 

 it breaks into a flame, a round ring is scorched on the paper correspond- 

 ing to the two outer coats of the 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 unscorched 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 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 ascend- 

 ing currents of air strike it to the best advantage, and insures good com- 

 bustion 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 combustion takes 

 place in them. In the one next the dark center the carbon particles as 

 has been said are passing through and glow with a bright light. They 

 are completely burned in the outer coat. 



