THE CONQUEST OF NATURE 



purposes. The principle was correct, but the construc- 

 tion of the mantle was defective. 



Meanwhile a German scientist, Dr. Auer von Wels- 

 bach, who had become famous in the scientific world 

 for his researches on rare metals, was experimenting 

 with certain oxides of different metals, and developing 

 a method of handling them that finally resulted in the 

 perfected incandescent burner in use at present. His 

 process, which in theory at least was not entirely original 

 with him, was to dip an open fabric of cotton into a 

 solution of the nitrates of the metals to be used, drying 

 it, and converting the nitrates into oxides by burning; 

 the cotton fabric disappearing but leaving the skeleton 

 of the oxide, which retained its original shape. 



At the same time corresponding improvements were 

 made in the type of burner, which is quite as essential 

 to success as the mantle itself. It had been found that 

 it was absolutely essential for such a burner to give a 

 practically non-luminous flame, as otherwise the deposit 

 of carbon particles will ruin the mantle. Two ways of 

 obtaining this are possible; one by mixing a certain 

 quantity of air with the gas before combustion, the other 

 to burn the gas in so thin a flame that the air permeates 

 it freely. Several burners of both types were used at 

 first, but gradually the burners in which the air is 

 mixed with the gas became the more popular, and most 

 of the incandescent burners now on the market are of 

 this type. 



In the construction of mantles at the present time, 

 while the principle of their use remains the same as that 

 of the lime-light, lime itself is not used, the oxides of 



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