350 
DR W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 
Xenon .—Xenon also shows two spectra, without capacity in the red region and 
with it, extending far into the ultra-violet. Practically the only material at disposal 
is contained in the extensive lists of Baly* (red spectrum 6198—-2536, hliie 
6097—-2414) with an accuracy of about '03 A. This is supplemented by observations 
by Liveing and Dew^ar,! especially by longer wave-lengths up to 6596, but 
unfortunately only measured to the nearest unit. 
Baly draws attention to the large number of lines apparently common to both 
Kr and X. The number of lines in the whole spectrum is very large. Baly gives 
1376 in the blue spectrum, hut perhaps the most noticeable point for our present 
purpose is the great variability with change in the conditions of excitation. This is 
very clearly indicated by a comparison of intensities of corresponding lines as observed 
by L., D. and B. The following are a few examples out of a large number illustrating 
this. The numbers following a wave-length give the intensities as estimated 
respectively by Baly and by Liyeing and Dewar 
5191 
5, 6 
4890 
5, 
3 
5188 
4, 3 
4887 
5, 
0 
5080 
7, 2 
4884 
1, 
4 
5068 
not seen, 5 
4883 
6, 
0 
5045 
3, 6 
4844 
10, 
10 
As between the tAvo spectra also, a fact noticed by L. and D. is of importance. 
They say “ there is one very remarkable change in the xenon spectrum produced by 
the introduction of a jar into the circuit. Without the jar the xenon gives two 
bright green rays at about X4917 and A4924, but on putting a jar into the circuit 
they are replaced by a single, still stronger, line at about 4922. In no other case 
have we noticed a change so striking.” They also state that changes occur with the 
same kind of discharge as between different tubes. These are clear cases of oun 
displacements. Paulson again {loc. cit.) gives some constant separations in the first 
spectrum. The triplet separations observed are about = 1778, j/g = 814, in due 
order of magnitude with those for Kr. No line suitable for S (l) comes within the 
observed region, but there are two lines with W.N. 40375’40, 39561'50 separated by 
813‘99, which would serve for 82 ( 1 ) and 83 ( 1 ) and are in a similar position to the 
KrS lines. They clearly suggest that the Si(l) line is at —42153'39, using 
vi = 1777’90 as found from the Sg set. This is further substantiated by employing 
the value of the e link, found below to he 7314, as a sounder. It requires a line at 
about 34839, and such a line is found at (< l) 3483678 (but see discussion under 
* ‘ Phil. Trans.,’ A, vol. 202, p. 183 (1903). 
t ‘Roy. Soc. Proc.,’ vol. 68, p. 389 (1901); ‘ Coll. Papers,’ p. 494. 
/ 
