228 Profs. Liveing and Dewar. [May l l J, 



6461*98. Not down as an iron line in Thalen's list. If it be an iron 

 line, we are unable to distinguish it from the calcium line (see 

 Appendix). 



5601*84. The iron line in this double is less refrangible than the 

 calcium line. 



5597*31. A rather close double in which the iron line is the more 

 refrangible. 



5348' 75. Clearly double, the iron line less refrangible than the 

 calcium line. 



5269*59. A very close double, the iron line less refrangible than 

 the calcium. 



5041*32. A close double, but distinctly separable, the iron line 

 the less refrangible. Kirchhoff gives the iron and calcium lines as 

 separate, but the calcium line less refrangible than the iron. 



4877*57. We could not resolve this line ; though Young has resolved 

 the corresponding solar line. 



4585*36 ~) There are no iron lines at these places in Thalen's list, nor 



4578*37 r could we detect any in the arc though the positive 



4580*93 J pole was of iron. 



4407*8 seems to be an iron line, though not in Thalen's list, but the 

 calcium line, if there be one at this place in the arc, is so faint that we 

 could not certainly make it out. 



4379*16 also seems to be an iron line not in Thalen's list, but we 

 could find no calcium line in the arc corresponding to it. 



4375*46 is not given as a calcium line in Thalen's list, and we could 

 see no calcium line at this place. 



4307*25 seems to be a very close double, not distinctly divisible, as 

 both lines are somewhat diffuse, but the iron a little less refrangible 

 if it expands symmetrically, and so given by Kirchhoff and by Thalen. 



4301*95. The iron line here is faint, and it is more refrangible than 

 the calcium line. 



4298*56. Close but distinctly divisible double, the iron less 

 refrangible than the calcium line. 



4271*33 had the appearance of a very close double, as when calcium 

 chloride was introduced into the crucible, the line expanded more on 

 its less refrangible side, as if the iron line were rather more refrangi- 

 ble than the calcium line ; but we could not definitely separate the two. 

 The two lines are not given as exactly coincident by Thalen. 



The lines 4249*81, 4246*89, 4233, 4143*14, 4131*52 are doubtful 

 calcium lines ; at least, we could not detect any such lines when 

 calcium chloride was introduced into the arc, though the other calcium 

 lines in the neighbourhood were well developed. 



4097*55 does not seem to be an iron line, and we could detect no 

 such line in the arc when the positive pole was of iron. 



Of supposed common lines of nickel and iron : — 



