PRELIMINARY EXPERIMENTS xxiii 



unburned wood, and yet it can be found when the wood is 

 partly burned. 



Why, now, is the glass blackened when held in the flame 

 and not when held directly above it? It is because the 

 carbon from the candle has not been completely burned 

 at the middle of the flame ; but it is burned beyond the 

 bright part of the flame. When the glass is held in the 

 flame, the carbon that is not yet completely burned is de- 

 posited on it, because it is cooler than that in the surround- 

 ing flame. 



A fine deposit of carbon can be had from any of the 

 luminous parts of the flame ; and it is these thousands of 

 little particles of carbon, getting white hot, which glow 

 like coals in the stove and make the light. Just as soon 

 as they are completely burned, there is no more light, as 

 coals cease to glow when burned to ashes. 



III. Carbon dioxid 



Let us now inquire what becomes of the carbon that we 

 find in the bright part of the flame and of the oxygen that 

 was in the air in the lamp chimney. When the candle was 

 extinguished within the chimney, there was no oxygen left, 

 as shown by the lighted splinter, which was put out immedi- 

 ately. Neither could any of the particles of carbon be 

 found except on the wick. Yet they both still exist within 

 the chimney, but in an entirely different condition. While 

 the candle was burning, the little particles of carbon that 

 we find ascending in the flame are joining with the oxygen 

 of the air and making an entirely new substance. This 

 new substance is a gas and cannot be seen in the air. 



Of what two substances is this new substance made? 

 It is CO 2 . 



