462 Mr. J. N. Lockyer. On the Spectrum of Carbon. [May 27, 



battery) from carbon poles in an atmosphere of chlorine, the blue 

 Sittings alone are visible, while, when the spark is similarly photo- 

 graphed, the nltra-violet flutings and the blue line (4266) are also 

 visible, while the bine flutings become fainter. 



From this we may assume, in accordance with the working hypo- 

 thesis of a series of different temperature furnaces, as set forth in the 

 paper of December, 1878 (see fig. 1), that the different flutings and 

 the line correspond to different temperature spectra, the blue flutings 

 to the lowest and the blue line to the highest temperature, while the 

 ultra-violet flutings occupy an intermediate position. 



Fig. 2. 



Spectra of the hypothetical substance in intermediate furnaces, assuming that the 

 vapours are not completely dissociated. 



According to this working hypothesis, there should be a series of 

 heat-levels forming a perfect gradation between the spectrum which 

 contains the blue line alone and that which contains the blue flutings 

 alone (fig. 2). 



In comparing the spectra of carbon under different conditions, I 

 find this to be true. The blue line never appears in conjunction with the 

 blue flutings, unless the ultra-violet flutings are also present. In other 

 words, the highest and the lowest hypothetical temperature spectra are 

 never visible together without the spectrum of the intermediate hypo- 

 thetical temperature. 



But this is not all. By placing the spectra of the substances at 

 different heat-levels, so to speak, I am enabled to construct a diagram 

 which not only indicates the mere presence or absence of the lines and 

 their relative intensities, but shows that there exists a perfect grada- 

 tion between the spectrum which contains the line alone and that 

 which contains the blue flutings alone (fig. 3). I would point out 

 that there is nothing theoretical in this diagram. All the heat-levels 



