366 LETTERS ON NATURAL MAGIC. 



Professor 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 part of the wick became red hot, and con- 

 tinued so while a drop of alcohol remained, and provided 

 the air in the room was undisturbed. On one occasion 

 the wick continued red hot for twenty-four hours, and a 

 very disagreeable acid vapour was formed. 



On these principles depend the lamp without flame 

 which was originally constructed by Mr. Ellis. It is 

 shown in the annexed figure, where A B is the lamp, and 

 A a cylindrical coil of platinum wire, the hundredth part 



Fig. 74. 



of an inch in diameter. This spiral is so placed that four 

 or five of the twelve, coils of which the cylinder consists 

 arc upon the wick, and the other seven or eight above it. 

 If the lamp is lighted, and continues burning till the 

 cylindrical coil is red hot, then if the flame is blown out, 

 the vapour which arises from the alcohol will by its com- 

 bustion keep the coils above the wick red hot, and this 

 red heat will in its turn keep up the vaporisation of the 

 alcohol till the whole of the alcohol is consumed. The 

 heat of the wire is always sufficient to kindle a piece of 

 German fungus or saltpetre paper, so that a sulphur match 

 may at any time be lighted. Mr. Gill found that a wick 

 composed of twelve threads of the cotton yarn commonly 



