THE STRUCTURE OF THE SERIES OF LINE- AND BAND-SPECTRA. 589 
all the Cyanogen-bands, but this conclusion is evidently negatived by the last series at 
A= 3590 mentioned in the preceding table, where the edges of the corresponding heads 
and tails would then be turned towards each other, 7.e. the lines would not be within 
the space between head and tail. We notice also that Dr JuncBiury’s relation applies 
as well to the differences between the heads of the four Cyanogen-bands when compared 
one with the other. Thus: 
4606 — 4216 = 390 4216 - 3884=332 
7 
4578 — 4197 = 381 ; 4197 — 3872 = 325 
4553 — 4181 =372 3 4181 — 3862=319 P 
4532 — 4168 = 364 4168 — 3855 = 313 
The most probable conclusion would therefore be that the alleged relation constitutes 
a property of the “heads” of the bands, and that Mr Kuine’s shadings should be con- 
sidered as the edges of a new band of the Cyanogen-spectrum, and not as the tails of 
the band at > = 3884. 
In concluding this section of my investigations dealing with the band-spectra, I may 
point out another form of the Rypperc-THieLe formula which, though somewhat more 
complicated in appearance, reveals well its significant structure. Using wave-lengths 
we may write the equation in the form 
je ees (14) 
where n stands for (m+) and where y denotes a constant. We notice without 
difficulty that for \,=0, 2.e. when 
——— (15) 
the formula becomes identical with RypBErRGe’s equation for line-spectra, which again, on 
the further supposition that n represents integers, assumes the well-known form of 
BALMER’S equation. So far, it is true, the observations have shown no evidence of 
Series to which the positive sign in the denominator is applicable. In other words, 
no line-series have yet been found progressing from the violet towards the red, 2.e. 
having their heads on the violet, and their tails on the red side of the spectrum. But 
the present investigation points now to the possibility of such regularities, and may 
perhaps induce physicists to search for series of this character. 
If, on the other hand, we suppose A» = 0, equation (14) assumes the form 
r 
Ne: Of (16) 
n\2 
1+(7) 
which becomes identical with Drstanpres’ formula for band-series, if we assign to n 
integer values. The positive sign expresses that the band shades off towards the violet, 
