234 THE CHEMISTRY OF THE SUN. [CHAP. 



after all this work had been accomplished. It gives a list of 

 the iron lines in a small part of the spectrum, which, after 

 making every allowance for the existence of impurities, we 

 found to coincide with lines in other substances. 



It will be seen, to take some instances from the above table, 

 that the two short lines 390600 and 395423 coincided, the 

 first with short lines in uranium, zirconium, and yttrium, the 

 second with short lines in uranium, molybdenum, and tungsten. 

 Similarly there are two short-line coincidences with zirconium, 

 and no less than six with vanadium, and so on. The total 

 gives the coincidences of the lines of all the elements under the 

 conditions that I have drawn attention to. So that the sum 

 total of this really very laborious inquiry with regard to iron was, 

 first, that in the region between 39 and 40, the region including 

 H and K, where, before the introduction of photography, scarcely 

 any iron lines had been seen, and where only five solar lines 

 had been given in Angstrom's atlas, photography gave us a total 

 of nearly 300 lines in the solar spectrum, and it gave us sixty- 

 two lines of iron. 



Next, of those sixty-two lines of iron only eighteen were what we 

 then considered normal ; by which I mean that the remainder had 

 short-line coincidences with lines of other substances. So that 

 the idea first thrown out by Kirchhoff, Angstrom, and Thalen of 

 the possibility of the coincidence of lines among the metallic 

 elements seemed entirely endorsed. It will be seen that it is 

 the rule in the case of iron, and it might be the case also in 

 other substances. The fact of a line not being coincident with 

 a line in another substance was the exception, and not the rule. 

 The ratio in the case of iron being as 44 to 18 over the region 

 examined. 



I now proceed to give the results in the case of titanium. 

 We got one case of three coincidences, five cases of two, and 

 ten of one coincidence : 



