CHEMICAL HISTORY OF A CANDLE in 



luminous. I have here taken three or four examples apart 

 from the candle on purpose to illustrate this point to you, 

 because what I have to say is applicable to all substances, 

 whether they burn or whether they do not burn that they 

 are exceedingly bright if they retain their solid state, and 

 that it is to this presence of solid particles in the candle- 

 flame that it owes its brilliancy. 



Here is a platinum wire, a body which does not change 

 by heat. If I heat it in this flame, see how exceedingly 

 luminous it becomes. I will make the flame dim for the 

 purpose of giving a little light only, and yet you will see 

 that the heat which it can give to that platinum wire, though 

 far less than the heat it has itself, is able to raise the plati- 

 num wire to a far higher state of effulgence. This flame 

 has carbon in it; but I will take one that has no carbon in 

 it. There is a material, a kind of fuel a vapor or gas, 

 whichever you like to call it in that vessel, and it has no 

 solid particles in it; so I take that because it is an example 

 of flame itself burning without any solid matter whatever; 

 and if I now put this solid substance in it, you see what an 

 intense heat it has, and how brightly it causes the solid body 

 to glow. This is the pipe through which we convey this par- 

 ticular gas, which we call hydrogen, and which you shall 

 know all about the next time we meet. And here is a sub- 

 stance called oxygen, by means of which this hydrogen can 

 burn; and although we produce, by their mixture, far 

 greater heat( 8 ) than you can obtain from the candle, yet 

 there is very little light. If, however, I take a solid sub- 

 stance, and put that into it, we produce an intense light. If 

 I take a piece of lime, a substance which will not burn, and 

 which will not vaporize by the heat (and because it does not 

 vaporize remains solid, and remains heated), you will soon 

 observe what happens as to its glowing. I have here a most 

 intense heat produced by the burning of hydrogen in con- 

 tact with the oxygen; but there is as yet very little light 

 not for want of heat, but for want of particles which can 

 retain their solid state; but when I hold this piece of lime 

 in the flame of the hydrogen as it burns in the oxygen, see 



8 Bunsen has calculated that the temperature of the oxyhydrogen blow- 

 pipe is 8061 Centigrade. Hydrogen burning in air has a temperature of 

 3*59 C., and coal-gas in air, 2350 C 



