578 



Dr. W. Huggins. 



[June 17, 



I have since that date taken a large number of photographs of the 

 spectra of different flames, in the hope of being able to present the 

 results to the Royal Society, when the research was more complete. I 

 think now that it is desirable that I should describe the spectrum of 

 the flame of hydrogen, but I shall reserve for the present the experi- 

 ments which relate to the presence of carbon and its compounds. 



The spectrum of the flame of hydrogen burning in air is represented 

 in the diagram, Spectrum No. 1. It consists of a group of lines which 

 terminates at the more refrangible limit in a pair of strong lines, 

 \ 3062 and X 3068. At a short distance, in the less refrangible direc- 

 tion, what may perhaps be regarded as the group proper, commences 

 with a strong line, A. 3090. Between the strong line X 3068 and the 

 line X 3090 there is a line less bright, X 3080. Less refrangible than 

 the line X 3090 are finer lines at about equal distances. The lines are 

 then fine and near each other, and appear to be arranged in very close 

 pairs. There is a pair of fine, but very distinct lines, X 3171 and 

 X 3167. In this photograph the group can be traced to about X 3290. 

 This group constitutes the whole spectrum, which is due probably to 

 the vapour of water. 



I then introduced oxygen into the flame, leaving a small excess of 

 hydrogen. A spectrum in all respects similar came out upon the 

 plate. I repeated the experiment, taking both spectra on the same 

 plate. Through one-half of the slit the spectrum of the oxyhydrogen 

 flame was taken. This flame was about 7 inches long, and the 

 spectrum taken of a part of the flame 2 inches from the jet. The 

 oxygen was then turned off, and the quantity of hydrogen allowed to 

 remain unaltered. A second spectrum with an exposure of the same 

 duration was then taken through the second half of the slit. On the 

 plate the two spectra are in every respect similar, and have so exactly 

 the same intensity, that they appear as one broad spectrum. 



In all these experiments a platinum jet which had been carefully 

 cleaned was used. 



In these experiments the two gases met within the blowpipe and 

 issued in a mixed state. 



The jet was removed, and a flame of hydrogen was surrounded 

 with oxygen. The spectrum, No. 2 in the diagram, shows some addi- 

 tional lines. In this case the jet was brass, and in this or some other 

 way impurities may have been introduced ; and I should, at present, 

 incline to the view that the additional lines about X 3429 and X 3473, 

 and the groups more refrangible than X 3062, do not belong to the 

 water spectrum, but to impurities. 



Coal-gas was substituted for hydrogen in the oxyhydrogen blow- 

 pipe, and oxygen admitted in as large a proportion as possible. The 

 inner blue flame rising about 2 inches above the jet showed in the 

 visible part of the spectrum the usual " five-fingered spectrum." The 



