On the Chemistry of the Hottest Stars. 



195 



Professor Pickering announced last month that the star £ Puppis 

 contained, in addition to the usual series of hydrogen lines, a second 

 series of rhythmical lines, which he supposed to be due to a new 

 element. On further inquiry, it was found that the lines were closely 

 allied to the hydrogen series, and that it was probably due to that 

 substance under conditions of temperature or pressure as yet un- 

 known. 



His basis for this statement was founded on the fact that the 

 wave-lengths of the new series could be directly computed by sub- 

 stituting for the value of n in the formula which gave us the known 

 hydrogen series even numbers instead of odd ones.* 



Now, this new series of hydrogen has, so far as we know, only 

 been seen in one other star, namely, 29 Canis Majoris. 



Professors Pickering and Kayser both concede that this new form 

 of hydrogen is due most probably to a high temperature, so that we 

 should expect to find it in the bright-line stars, which, on the meteo- 

 ritic hypothesis, give us the effect of the highest temperature, due to 

 the possibility of end-on collisions without the shielding effects of 

 gaseous envelopes." Kayser expressly states,f " that this series has 

 never been observed before, can perhaps be explained by insufficient 

 temperature in our Geissler tubes and most of the stars." 



It seems as if the two series are of the " subordinate" type, and 

 that the principal series is still wanting, because in subordinate 

 series the lines for large values of n lie very near to one another, the 

 principal series on the other hand terminates more in the ultra-violet. 

 It seems, therefore, probable that one or two of the many unknown 

 lines recorded in stellar spectra may belong to the principal series of 

 hydrogen, but that they have not as yet been identified as such. J 



* The two series are as follows : — 



Old Series. New Series. 



Observed 



n. 



Computed. 



Observed. 





Computed. 



(means). 



6 



6563 -0 



6563 -0 



5 



10128-1 





8 



4861-5 



4861 -5 



7 



5413 -9 





10 



4340-6 



4340 -7 



9 



4543-6 





12 



4101 -9 



4101 -8 



11 



4201 -7 



4200 -4 



14 



3970 -2 



3970 -2 



13 



4027-4 



4026-8 



16 



3889 -2 



3889 -1 



15 



3925 -2 



3924-7 



18 



3835 -5 



3835 -5 



17 



3859-8 



3858 -7 



20 



3798-0 



3798-1 



19 



3815-2 



3815 -9 









21 



3783 -4 



3783 -4 



These figures are taken from Professor Pickering's article in ' Astrophysical 

 Journal,' vol. 5, p. 93. See also Kayser' s article on p. 95 of the same journal, 

 f ' Astrophysical Journal,' vol. 5, p. 96. 



X I find that this conclusion has already been in part arrived at by Kayser 

 ('Astrophysical Journal,' vol. 5, p. 93). 



VOL. LXr. P 



