80 Mr Talbot's Experiments on Coloured Flames. 



so remarkable that alcohol burnt in an open vessel, or in a 

 lamp with a metallic wick, gives but little of the yellow light ; 

 while, if the wick be of cotton, it gives a considerable quanti- 

 ty, and that for an unlimited time. (I have found other in- 

 stances of a change of colour in flames, owing to the mere pre- 

 sence of a substance which suffers no diminution in conse- 

 quence. Thus, a particle of muriate of lime on the wick of a 

 spirit lamp will produce a quantity of red and green rays for 

 a whole evening, without being itself sensibly diminished.) 

 The bright flame of a candle is surrounded by the same ho- 

 mogeneous yellow light, which becomes visible when the flame 

 itself is screened. The following experiment shows its na- 

 ture more evidently : If some oil is dropped on the wick of a 

 spirit lamp, the flame assumes the brilliancy of a candle sur- 

 rounded by an exterior yellow flame. This appearance only 

 lasts until the oil is consumed. 



4. The flame of sulphur and nitre contains a red ray, which 

 appears to me of a remarkable nature. While examining the 

 yellow line in the spectrum of this flame, I perceived another 

 line situated beyond the red end of the spectrum, from the 

 termination of which it is separated by a wide interval of dark- 

 ness. In colour it nevertheless differs but little from the rays 

 which usually terminate the spectrum. It arises, I believe, 

 from the combustion of the nitre, as the yellow ray does from 

 that of the sulphur, for I have since observed it in the flame 

 of a spirit lamp, whose wick had been soaked in nitre or chlo- 

 rate of potash. It appeared to me that this ray was so dis- 

 tant from the rest, that it might be less refrangible than any 

 in solar light ; and I have been since informed by Mr Her- 

 schel, that he had already observed it in a similar experiment, 

 and was impressed with the same idea. 



With the hope of establishing this, I admitted candle light, 

 and that of the nitre lamp which I have just mentioned, 

 through the same aperture, and noticed how far this isolated 

 red ray appeared beyond the spectrum of the candle. I then 

 compared, in the same way, the light of the candle with that 

 of the sun, and I found that the great intensity of the solar 

 lio-ht lengthened the red end of the spectrum about as far, so 



that I was obliged to leave the question undecided, as the 



11 



