204 



Mr. J. N. Lockyer. 



[May 12, 



In the next horizon are entered the frequencies with which iron 

 lines were seen in observations of a hundred flames by Tacchini. In 

 both these horizons the lengths of the lines represent frequency. 



This map shows that within the region F to b, there is no line com- 

 mon to spots and flames, if the lines & 3 & 4 , which are so frequently seen 

 affected in both spots and flames, be neglected. If, therefore, we were 

 unacquainted with the spectrum of iron, we should be justified in say- 

 ing that the spectrum of the prominences was due to one substance, 

 and that of the spots to another.* 



In a paper presented to the Royal Society in December, 1878, I 

 drew attention to the fact that many of the lines most frequently seen 



o 



in the flames by Young and Tacchini were assigned by Angstrom to 

 the spectra of two so-called elements. In the map I have entered his 

 results in the horizon arc A. 



I have since that time had prepared a table, showing the lines 

 having coincident readings in two or more metals, according to Thalen, 

 and in my paper of March 5th, 1879, " Discussion of Young's List of 

 Chromospheric Lines," showed that some of these lines could not be 

 due to impurity. The lines given coincident by Thalen in his tables, 

 are entered in the horizon spark T. 



I have confirmed in most cases Thalen's and Angstrom's work, and 

 have proved that these lines could not be due to an impurity of the 

 one in the other, as the longest lines of each were absent from the 

 other. I used the arc, quantity coi], and intensity coil, which are 

 respectively indicated by arc L, spark LQ, and LI, with high dis- 

 persion. 



Besides confirming Thalen's and Angstrom's work, I have been able 

 to add a few more basic lines to the list. 



I have already pointed out that the fact of different rates of motion 

 being indicated by different iron lines in the same field of view at the 

 same time, afforded important evidence that we were not dealing with 

 iron itself, but with primitive forms of matter contained in iron, which 

 are capable of withstanding the high temperature of the sun, after 

 the iron, observed as such, has been broken up as suggested by Brodie.f 



An appeal to the principles of continuity and evolution now enables 

 us to add another argument of equal weight. If on the cooling of a 



* It will be observed that the line at 5017'5 given among the flame observations in 

 the map is not recorded as an iron line by either .Angstrom or Thalen. The way, 

 however, in which it sympathised with the line at 4923 in the flames induced me to 

 look for it in iron with the intensity coil. I at once found it, and it is as sympa- 

 thetic with the fine at 4923 in the spark as it is in the flames themselves. Though 

 omitted by Thalen (most likely accidentally, thougn it may well be that he did no I; 

 iise sufficient tension to bring it out strongly) , it is recorded as an iron line by other 

 observers. 



f Or rather, of course, before " iron " had been formed by condensation. 



