442 



Mr. J. N. Lockyer. Discussion of [Mar. 20, 



direction, since, as I have been anxious to avoid any question arising 

 from the known impurity of carbon poles, I have limited myself 

 to the use of double metallic poles or experimented on very volatile 

 substances, the impurities carried up by which are easily detected. *I 

 append a provisional table of the results I have already obtained. I 

 do not hold to its absolute accuracy, but I know it is sound in the 

 main. (See p. 443.) 



The dispersion I have employed (Rutherford's grating, 17,000 lines 

 second order) has been so great that the observations would have 

 been more satisfactory if the light of the arc had been less reduced 

 by dispersion. We may therefore feel assured that we are dealing 

 with lines of the same wave-length, identical, that is, within the 

 range of the most powerful instrumental methods ordinarily employed. 

 In all cases a battery of thirty Grove cells was used, and the lines 

 were successively observed at the intersection of two cross-wires 

 in the field of view, everything remained unchanged and rigid except 

 the poles between which the arc was made to pass. For the lines 

 between H and G an inspection of photographs has taken the place of 

 eye observations, and for this not only my own series of photographs 

 has been used, but a most valuable one placed at my disposal by Pro- 

 fessor Roscoe. 



The list in its present very incomplete state leads to very remark- 

 able conclusions; the line at 1474 has been found in several spectra, 

 while Lorenzoni's / is markedly absent from the spectra of forty-two 

 metallic elements ; this result, I think, justifies the suspicion long ago 

 stated that / belongs to the same substance, or at least is nearly related 

 to that which produces D 3 . It will be seen too that a line coincident 

 with the h line of hydrogen has been photographed in the spectra of 

 several substances besides indium, G being absent, and F also, as I 

 have gathered from an inspection of Dr. Roscoe's photographs. I may 

 add that I have reason to suspect the existence of the C line alone in 

 the spectra of some chemical substances. 



These observations have compelled me to make rapid surveys of the 

 arc-spectra of most of the metallic elements, and have again brought 

 to the front, in a very striking way, the view I expressed to the Royal 

 Society some five or six years ago, that many of the lines in line- 

 spectra are the brightest portions — the remnants — of flutings and 

 possibly of other rhythmic structure. I am at present engaged in 

 investigating this question of rhythm, and I have already found that 

 many of the first order lines of iron may probably arise from the 

 superposition or integration of a number of rhythmical triplets. All 

 this goes to show how long the series of simplifications is that we 

 bring about in the case of the so-called elementary bodies by the 

 application of a temperature that we cannot as yet define. Indeed 

 the more one studies spectra in detail, and especially under varying 



