CREW AND BAKER. — SPARK SPECTRUM OP CARBON. 403 



appear in the spark spectra of elements in air at barometric pressure. At 

 first we took the band at A. 3371.1 to be a hitherto undescribed carbon 

 band ; and it was only through an excellent suggestion from Professor 

 Hale that we discovered our mistake. He advised us to try the spark 

 without capiacity. On trying this experiment, we found the band at 

 X 3371.1 strongly present in the spectra of aluminium, zinc, and other 

 metals in air ; but when the spark was worked in atmospheres of oxygen 

 or coal gas, these flutings all disappeared save the merest trace of the 

 strongest two. 



The cold carbon spark (unlike that of metals) without capacity shows 

 these bands only with extreme faintness ; and the condensed carbon 

 spark does not show them at all ; but carbon when white hot shows them 

 strongly, as indicated above. 



In this connection,- the question may be raised whether the band de- 

 scribed by Professor Hutchins * does not belong to this nitrogen group. 

 For we have found in the spark spectrum of aluminium a band, with 

 its edge at A. 3914.41, which shows a weak line alternating with a strong 

 one exactly as in Hutchins's photograph. But on examining this spark 

 in a current of oxygen, not the slightest trace of the band was found. 

 Since it is found in metals, but not in the carbon spark, and since it 

 disappears when nitrogen disappears, it seems to us more probably due 

 to nitrogen f than to carbon. 



What is apparently the same band may be seen very distinctly on 

 McClean's map of the spark spectrum of copper; and again a similar 

 fluting has been found by Deslandres at the negative electrode of a 

 spectrum tube filled with nitrogen. For Deslandres' drawing see 

 Comptes rendu s, 9 Aug., 1886. This is probably also the same band 



* Hutchins, Astropliysical Journal, 15, 310 (1902). 



t Mr. F. J. Truby lias measured the first 14 lines of this fluting, wjiich form a 

 group lying between tlie edge and the heavy impurity line at A 3905.74. His 

 values are as follows : 



3914.41, head 3909.95, weak 



3913.89 3909.30, strong 



3913.35 3908.52, weak 



3912.62, strong 3907.80, strong 



3912.17, weak 3906.88, weak 



3911.70, strong 3906.1G, strong 



3911 17, weak 3905.74, impurity 

 3910.61, strong 



There are possibly two otlicr weak lines near the head wliich Mr. Truby's definition 

 does not permit him to measure. 



