236 Mr. J. N. Lockyer. On the Classification [Jan. 10, 



Fig. 19 shows how the aurora spectrum can be built up from the 

 lowest-temperature spectra of manganese, magnesium, lead, and 

 thallium, and the brightest flutings of carbon. 



When the temperature is increased iron (615) sometimes flashes in. 

 This was particularly noticed in the Norwegian observations, to which 

 I have subsequently to refer. 



VI. Further Discussion of Gyllenskiold' s Observations. 



Tf, in discussing Gyllenskiold's observations, we limit ourselves to 

 those cases in which not more than four lines were recorded, we find 

 that with a few exceptions, the lines seen were lines which are 

 brightest in the spectra of meteorites at low temperatures. It might 

 at first sight be expected that when only a few lines are seen, they 

 ought to be the same in every case. There are variations, however, 

 which in all probability are due to differences in composition of 

 ditferent groups of meteorites. 



The following tables contain all the observations in which not more 

 than four lines were recorded. The probable origin of each line is 

 also stated. Some of the lines have been arranged in different 

 columns, as the discussion has suggested. 



It will be observed that the characteristic line was seen alone eight 

 times by Gyllenskiold out of the thirty-eight observations recorded 

 in the first table. 



Out of the total number of seventy-six observations in the tables, 

 the line of manganese at wave-length 540. which is seen in the 

 spectra of many of the " bright line stars," was seen alone on two 

 occasions, and six times in company with other lines. 



The first fluting of lead, at wave-length 546, occurs alone three 

 times, is twice associated with the thallium line, and occurs six times 

 along with other lines. 



The remnant of the magnesium fluting at 500 occurs alone only 

 once, but that at 521 occurs alone six times. 



The first fluting of carbon, at 517, occurs alone three times, and 

 twice in company with other lines. The carbon band extending from 

 468 to 474 occurs alone four times, and six times with other lines. 

 The low-temperature fluting of carbon at 483 only occurs once, and 

 is then alone. The first iron line at 579 occurs alone twice, and six 

 times along with other lines, When we get iron apparently without 

 manganese 558 it is probably due to masking of 558 by continuous 

 spectrum. The green line of iron at 527 occurs alone seven times, 

 and thirteen times in company with other lines. 



The thallium line appears alone only once, but in company with 

 other lines it appears fifteen times. 



