XX11 



GENERAL INTRODUCTION 



to be understood, the following questions, together with 

 any others which suggest themselves, may be asked: What 

 is the reason that draughts are opened in stoves ? Why is 

 the bottom of a " burner " on a lamp always full of holes ? 



II. Carbon 



Let us now observe the blackened end of a burned match 

 or splinter. This black substance is usually known by the 

 name of charcoal. If handled, it will blacken the fingers. 

 Try this. The same substance is found on the bottoms of 

 kettles which have been used over a wood fire, but it is 

 there a fine powder. 



Let us see what was burning when the candle was 

 lighted, besides the oxygen in the air. Relight the candle 



and hold the porcelain or glass about 

 an inch above the bright part of the 

 flame. What happens to it there ? 

 Next, lower it directly into the flame 

 (C). What is the black stuff that 

 gets on the glass ? Look closely and 

 see whether it is not deposited here 

 also as a fine powder. Will this de- 

 posit from the candle blacken the 



C. THE CARBON (OR 



SOOT) IS DEPOSITED 

 ON THE GLASS. 



fingers ? 



Instead of using the name charcoal for this black sub- 

 stance, let us call it carbon, the better name, because 

 there are several kinds of carbon, and charcoal is only 

 that kind which is rather light and easily blackens the 

 hands. 



The carbon from the candle flame came mostly from the 

 wax or tallow ; only a very small part came from the wick. 

 It cannot be seen in the tallow, neither can it be seen in 



