184 LETTERS ON NATURAL MAGIO. 



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 is 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 homo- 

 geneous 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 

 will last as long as there is gas in the reservoir. In place 

 of a collar of cotton wick, a hollow cylinder of sponge, 

 with numerous projecting tufts, may be used, or a collar 

 may be similarly constructed with asbestos cloth, and, if 

 thought necessary, it might be supplied with a saline 

 solution from a capillary fountain. 



Having thus obtained the means of illuminating any 

 apartment with yellow light, let the exhibition be made 

 in a room with furniture of various bright colours, with 

 oil or water coloured paintings on the wall. The party 

 which is to witness the experiment should be dressed in a 

 diversity of the gayest colours ; and the brightest coloured 

 flowers and highly-coloured drawings should be placed on 

 the tables. The room being at first lighted with ordinary 

 lights, the bright and gay colours of everything that it 

 contains will be finely displayed. If the white lights are 

 now suddenly extinguished, and the yellow lamps lighted, 

 the most appalling metamorphosis will be exhibited. The 

 astonished individuals will no longer be able to recognise 

 each other. All the furniture in the room and all the 

 objects which it contains will exhibit only one colour. 

 The flowers will lose their hues. The paintings and 

 drawings will appear as if they were executed in China 

 ink, and the gayest dresses, the brightest scarlets, the 

 purest lilacs, the richest blues, and the most vivid greens 



