110 



LETTERS ON NATUEAL MAGIC. 



of these flames is regulated by the cock I. The 



inflammation, therefore, of the ignited gas will be 



sustained by these four subsidiary flames through 



Fig. 22. 



which it passes, independent of any agitation of 

 the air, or of the force with which it issues from 

 the burner. On a projecting arm e h, carrying a 

 ring A, I fixed a broad collar, made of coarse 

 cotton wick, which had been previously soaked 

 in a saturated solution of common salt. When 

 the gas was allowed to escape at M, with such 

 force as to produce a long and broad column of 

 an explosive mixture of gas and atmospheric air, 

 the bluish flame occasioned by the explosion 

 passes through the salted collar, and is converted 

 by it into a mass of homogeneous yellow light. 

 This collar will last a long time without any fresh 

 supply of salt, so that the gas lamp will yield a 

 permanent monochromatic yellow flame, which 



