400 



Profs. Liveing and Dewar. 



[Nov. 27, 



but the reversal of the brighter pair of the group seems to militate 

 against such a supposition, as the third line has not been seen re- 

 versed . It is, however, much fainter than the other two. 



The sixth group consists of a pair of lines sharply denned, for which 

 we have found, by measurements of their distances from some bright 

 manganese lines in their neighbourhood, the wave-lengths 4751*4, 

 4747*5. The first only of this pair is described by Lecoq de Bois- 

 baudrau. We have not seen either of them reversed, but there are 

 lines in the solar spectrum which correspond closely to them and may 

 therefore reasonably be attributed to sodium. 



The seventh group is a pair of lines with diffuse edges, which we 

 have seen reversed as fine dark lines in the middle of the diffuse blue 

 bands. For these we deduced the wave-lengths 4667"2, 4663*7. The 

 first only is described by Lecoq de Boisbaudran, and he assigns to it 

 the wave-length 4670. By putting some titanic oxide into the crucible 

 the titanium line 4666*5 was seen between the sodium lines, and we 

 have no doubt that it is sodium which gives the winged appearance to 

 the corresponding ray in the solar spectrum. The ray 4663' 5 in the 

 " normal solar spectrum " is probably the other ray of this pair, as the 

 difference between the wave-length of this and that found by us is 

 within the limits of error in our measurements of such diffuse lines. 



The eighth group is a more sharply defined pair, for which by 

 measurement of their distances from neighbouring barium lines we 

 deduced the wave-lengths 4543*6, 4540*7. The lines 4543*9, 4540*2 

 in the " normal solar spectrum " probably represent this pair. 



The ninth group is again a diffuse pair for which we deduced, by 

 measurements from two bright manganese lines near them, the wave- 

 lengths 4496*4, 4494*5. These are too diffuse for very exact measure- 

 ment, but a bright line, which we could not certainly recognise as the 

 manganese line 4495, appears nearly coincident with the more re- 

 frangible of them. Lines nearly corresponding to these are in the 

 solar spectrum. 



The tenth group is again a more sharply defined pair, for which, by 

 measurements from calcium and iron lines, we found the wave-lengths 

 4423, 4419*5. The lines 2656*7, 2664-9 of Kirchhoff's map of the solar 

 spectrum may represent this pair. 



The eleventh group is a very diffuse pair, sometimes seen as a con- 

 tinuous band dividing as the sodium evaporates, for which we found 

 the wave-lengths about 4393, 4390. There is a line corresponding to 

 the former in the "normal solar spectrum," and Kirchhoff's line 2709*6 

 may represent the latter. 



The twelfth group is a diffuse but narrow band, which we have not 

 seen divided. The middle of it has a wave-length about 4343, very 

 nearly coincident with a line which we took to be an iron line, and 

 rather more refrangible than a chromium line 4344*5. 



