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Profs. G. D. Liveing and J. Dewar. [Dec. 21, 



which can be reached independently by the mere decomposition of 

 cyanogen or acetylene, then we may safely infer that the temperature 

 of individual molecules of carbon, nitrogen, and hydrogen in the 

 respective flames of cyanogen and acetylene may reach a temperature 

 of from six to seven thousand degrees. 



A previous estimate of the temperature of the positive pole in the 

 electric arc made by one of us, gave something like the same value. 



Farther evidence of the high temperature of the cyanogen flame is 

 afforded by the occurrence in the spectrum of that flame, when fed 

 with oxygen, of a series of flutings in the ultra-violet, which appear to 

 be due to nitrogen. The series consists of four, or perhaps more, sets, 

 each set consisting of a double series of lines overlapping one another. 

 The lines increase in their distance apart on the more refrangible side, 

 otherwise the flutings have a general resemblance to the B group of 

 the solar spectrum. The accompanying figure gives the general 

 appearance of two of the sets, but is not drawn to a scale. 



The four sets commence approximately at about the wave-lengths 

 2718, 2588, 2479, 2373 respectively. They are frequently present in 

 the spectrum of the arc taken in a magnesia crucible, and show 

 strongly in that of the spark taken without a condenser either in air 

 or nitrogen. As they appear in the spectrum of the spark in nitrogen, 

 whether the electrodes be aluminium or magnesium, and do not appear 

 when the spark is taken in hydrogen or in carbonic acid gas, they are 

 in all probability due to nitrogen. When a large condenser is used 

 they disappear. 



The formation of acetylene in ordinary combustion seems to be 

 the agent through which a very high local temperature is pro- 

 duced, and this is confirmed by the observations of Gouy on the 

 occurrence of lines of the metals in the green cone of the Bunsen 

 burner, which are generally only visible in spark spectra; on this 

 view acetylene is a necessary agent in the production of the flame 

 spectrum during combustion. The fact that when the arc is taken 

 in a magnesia crucible, although the cyanogen spectrum is strong, the 

 flame spectrum is often invisible, but may be made to appear by 

 introducing a cool gas or moisture, may be accounted for by an 



