160 THE CHANNEL AT NIGHT. 



"The heat produced by the burning in this case that is, 

 the chemical union of pure hydrogen and oxygen, is incon- 

 ceivably intense. There is scarcely any substance so re- 

 fractory as to endure it. Any substance, however, that can 

 sustain it, is raised to such an intense incandescence by the 

 heat that it emits a light of the most wonderful power. It 

 has been seen, it is said, at the distance of more than one 

 hundred miles in the daytime. 



" The light produced thus by an oxyhydrogen flame pro- 

 jected upon lime is sometimes called, from the source of 

 it, the oxyhydrogen light, and sometimes the lime or cal- 

 cium light, and sometimes the Drummond light, from the 

 name of the man who first discovered it, or, at least, who 

 first introduced it. 



"There is one curious circumstance in connection with 

 this subject," continued Lawrence, " which you can men- 

 tion in your recapitulation or not, just as you think best, 

 after you learn what it is, and that is, that it makes appar- 

 ently no difference what the solid substance is which is 

 raised to this intense incandescence in the various methods 

 adopted of heating them. The particles of carbon in the 

 Bude light, for example, are black when they are cold, but 

 they give out a none the less intense light on that account 

 when they are heated up to the requisite point. Indeed, 

 it is very curious that all solid substances, however differ- 

 ent they may be in chemical or mechanical properties, be- 

 gin to become luminous at the same temperature, and are, 

 so far as I know, equally brilliant at the highest tempera- 

 tures. The reason, therefore, for using lime is not because 

 it is white, but because it will stand the heat without melt- 

 ing. 



"But you must remember that while all solid substances 

 become incandescent at the same temperature, and emit, as 

 I suppose, the same quantity of light in comparison with 



