COMBUSTION WITHOUT FLAME. 310 



is here on fire, and this fire has continued for 

 nearly sixty years, and has resisted every attempt 

 that has been made to extinguish it. This fire, 

 which has reduced many acres of land to a mere 

 calx, arises from a burning stratum of coal about 

 four feet thick and eight or ten yards deep, to 

 which the air has free access, in consequence of 

 the main coal having been dug from beneath it. 

 The surface of the ground is sometimes covered 

 for many yards with such quantities of sulphur 

 that it can be "easily gathered. The calx has 

 been found to be an excellent material for the 

 roads, and the workmen who collect it often find 

 large beds of alum of an excellent quality. 



A singular species of invisible combustion, or 

 of combustion without flame, has been frequently 

 noticed. I have observed this phenomenon in 

 the small green wax tapers in common use. 

 When the flame is blown out, the wick will con- 

 tinue red-hot for many hours ; and if the taper 

 were regularly and carefully uncoiled, and the 

 room kept free from currents of air, the wick 

 would burn on in this way till the whole of the 

 taper is consumed. The same effects are not 

 produced when the colour of the wax is red. In 

 this experiment the wick, after the flame is blown 

 out, has sufficient heat to convert the wax into 

 vapour, and this vapour being consumed without 

 flame, keeps the wick at its red heat. A very 

 disagreeable vapour is produced during this im- 

 perfect combustion of the wax. 



Prof. Dobereiner, of Jena, observed that, when 

 the alcohol in a spirit of wine lamp was nearly 

 exhausted, the wick became carbonized, and 

 though the flame disappeared, the carbonized 



