114 FARADAY 



are those particles which you can easily see by holding a 

 piece of paper behind them, and which, while they are in the 

 flame, are ignited by the heat produced, and, when so 

 ignited, produce this brightness. When the particles are not 

 separated you get no brightness. The flame of coal-gas 

 owes its brightness to the separation, during combustion, 

 of these particles of carbon, which are equally in that as in 

 a candle. I can very quickly alter that arrangement. Here, 

 for instance, is a bright flame of gas. Supposing I add so 

 much air to the flame as to cause it all to burn before those 

 particles are set free, I shall not have this brightness; and 

 I can do that in this way: If I place over the jet this wire- 

 gauze cap, as you see, and then light the gas over it, it burns 

 with a non-luminous flame, owing to its having plenty of 

 air mixed with it before it burns; and if I raise the gauze, 

 you see it does not burn below. ( 10 ) There is plenty of 

 carbon in the gas ; but, because the atmosphere can get to it, 

 and mix with it before it burns, you see how pale and blue 

 the flame is. And if I blow upon a bright gas-flame, so as to 

 consume all this carbon before it gets heated to the glowing 

 joint, it will also burn blue. [The lecturer illustrated his 

 remarks by blowing on the gas-light.] The only reason why 

 I have not the same bright light when I thus blow upon the 

 flame is that the carbon meets with sufficient air to burn it 

 before it gets separated in the flame in a free state. The 

 difference is solely due to the solid particles not being sepa- 

 rated before the gas is burnt. 



You observe that there are certain products as the result 

 of the combustion of a candle, and that of these products 

 one portion may be considered as charcoal, or soot; that 

 charcoal, when afterward burnt, produces some other 

 product; and it concerns us very much now to ascertain 

 what that other product is. We showed that something was 

 going away; and I want you now to understand how much 

 is going up into the air ; and for that purpose we will have 



10 The " air-burner," which is of such value in the laboratory, owes its 

 advantage to this principle. It consists of a cylindrical metal chimney, cov- 

 ered at the top with a piece of rather coarse iron wire gauze. This is sup- 

 ported over an Argand burner in such a manner that the gas may mix in 

 the chimney with an amount of air sufficient to burn the carbon and hydrogen 

 simultaneously, so that there may be no separation of carbon in the flame 

 with consequent deposition of soot. The flame, being unable to pass through 

 the wire gauze, burns in a steady, nearly invisible manner above. 



