THE CONQUEST OF NATURE 



upon the regularity of the burning. As a finishing process 

 a flame is applied to the inside of the mantle after it has 

 cooled, to remove all traces of carbon that may remain. 



The mantle is now ready for use, but is so fragile that 

 it can scarcely be touched without breaking, and such 

 handling as would be necessary for shipment would be 

 out of the question. It is therefore strengthened tem- 

 porarily by being dipped into a mixture of collodion and 

 castor oil, which, when dry, forms a firm but elastic 

 jacket surrounding all parts. It is this collodion jacket 

 that is burned away when the new mantle is placed on 

 the burner before the gas is turned on. 



Quite recently the method of manufacturing mantles 

 used by Clamond has been revived. In this method the 

 cotton thread is dispensed with, the thread used being 

 made from a paste containing the mantle material itself. 

 The paste is placed in a proper receptacle the bottom 

 of which is perforated with minute openings, and sub- 

 jected to pressure, squeezing out the material in long 

 filaments. When dry these are wound on bobbins, 

 and, after being treated by certain chemical processes, 

 are ready for weaving into mantles. It is claimed for 

 mantles made on this principle that they last much 

 longer and retain their light-emitting power more uni- 

 formly than mantles made by the older process. 



THE INTRODUCTION OF ACETYLENE GAS 



When the incandescent mantle had been perfected 

 so as to be an economical as well an as efficient light- 

 giver, the position of coal gas as an illuminant seemed 



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