43 
raised when the above series are studied. In some cases we find, 
namely, a value given under 2, which occurs in two series. The 
corresponding values of 4) are then somewhat different as a rule. 
It is now the question : 
“Do the observed lines belong to two series, or have we to do 
with two lines close together, one of which is difficult to distinguish 
from the other?” 
Befcre answering this question I will first draw attention to this 
that this phenomenon is also met with in the spectra of other 
elements. Thus we find in the spectrum of aluminium *) 2 2204,73 
classed as n =8 in the 1st subordinate series, and as n= 7 in the 
2nd subordinate series; in that of Zinc ®) 4 2430,74 as n= 8 in the 
2nd component of the 1st subordinate series, and as n= 9 in the Ist 
_ component of the same series. In the spectrum of Calcium *) we 
find 23101,87 as n==8 in the 3rd component of the 2nd subordi- 
nate series, and as 72 = 9 in the 1st subordinate series, These few 
examples may suffice to show that the phenomenon that presents 
itself a few times in the series found by me, is met with elsewhere. 
Let us now try to answer the question raised led by the examples 
which present themselves in our case. 
Let us begin with the spectrum of Tin. 
For 4, 2483.50 we find 2, = 2412.53 in VII and 24, = 2482.49 in 
VIII. Examining the observation of this line we find given by KAYsER 
and Runer*): “2 umgekehrt”, and by Exner and HascumK *): “3 
unscharf, umgekehrt’. It is not impossible that here two different 
lines must be observed. Also what follows pleads in favour of this: 
In VII we find successively the intensities: 30, 10, 3, 3. That for 
ed the intensity is not found smaller than 3 may find its explanation 
in this, that two lines of slighter intensity give this increased intensity. 
For 2, 2408,27, which is given in I, with Ay = 2408,71, in III, with 
Ay = 2508.27, a similar explanation may hold. Kayser and Runes find *): 
“3 umgekehrt”’, Exner and Hascuexk *): “1 unscharf.” The course of 
intensity in I is: 5.3.1.1. Probably 7, = 2408.71 agrees therefore 
with a very faint line beside 4 2408,27, which belongs to III. 
Aw 2199.46, which has been given in VIII, with A, = 2199.32, 
and in IX, with A, = 2199.42, we find in Kayser and Runer ®) with 
the indication: “1 umgekehrt’, and in Exner and HascueEk*) in the 
J) Kayser, Handbuch der Spectroscopie. Vol. IL, p. 547. 
STe. ps o42. 
Sliep. Geo. 
4) Ueber die Spekiren der Elemente. VII. Abh. Berl. Akad. 1894. 
b) 1. ce Volk IL. 
6) Ee. Vols-iLt, 
