234 Mr. J. N. Lockyer. On the Classification [Jan. 10 y 



the oxy-coal-gas flame, and even with the purest electrolytic iron 

 prepared by Jacobi and by Professor Roberts-Austen it is visible 

 before the iron lines. The importance of this fluting in this discussion 

 cannot therefore be overrated. 



The aurora being a low-temperature phenomenon, we should expect 

 to find in its spectrum, lines and remnants of flutings seen in the 

 spectra of meteorites at low temperatures, the manganese fluting 

 being the most prominent for the reason before stated. 



The characteristic line of the aurora is the remnant of the brightest 

 manganese fluting at 558. Angstrom gave the wave-length of the 

 line as 5567, and since then many observers have given the same 

 wave-length for it, but probably without making independent deter- 

 minations. Piazzi Smyth, however, gives it as 558, which agrees 

 exactly with the bright edge of the manganese fluting. R. H. Proctor 

 also gives the line as a little less refrangible than Angstrom's deter- 

 mination. He says: "My own measures give me a wave-length 

 very slightly greater than those of Winlock and Angstrom" (' Nature/ 

 vol. 3, p. 468). 



Gyllenskiold's measures with the Wrede spectroscope also give 

 5580 as the wave-length of the characteristic line. I feel justified, 

 therefore, in disregarding the difference between the wave-length of 

 the edge of the manganese fluting and the generally accepted wave- 

 length of the aurora line. 



The line of manganese at 540, which is seen in the spectra of many 

 of the " stars " with bright lines, has been recorded in the aurora by 

 Vogel. 



The remnants of the two magnesium flutings seen in bodies of 

 Group II, at wave-lengths 500 and 521, are also seen as lines in the 

 aurora. In addition to these, there is sometimes the lead fluting at 

 546, corresponding to Duner's band 5, and probably also the green 

 line of thallium at 535, as indicated in the tables. 



Four lines in the aurora spectrum are probably due to carbon. The 

 first is at 516'5, the brightest fluting seen in the spectrum of a bunsen 

 burner; I have previously described this as a high-temperature 

 fluting, but the term is only relative. The second is the low- 

 temperature fluting at 483, which has been recorded by several 

 observers. There is probably also the high-temperature carbon 

 group beginning at 474, the maximum light of which is about 469. 

 Vogel records it as a band extending from 463 to 469, and Lemstrom 

 as 469 to 471. These observations, therefore, justify us in regarding 

 this as a band, and if we take the readings of the other observers as 

 the wave-lengths of the part of maximum brightness, we get the 

 mean reading of the maximum as 467'5. This agrees as well as can 

 be expected with the true wave-length of the maximum, 468. The 

 hydrocarbon fluting at 431 has probably also been seen. 



