A.—MATHEMATICS AND PHYSICS. Bil 
In terms of Bohr’s theory the 9-fold value of the Rydberg constant 
would be interpreted as meaning that aluminium atoms which emitted 
_ this spectrum had lost two electrons, and were represented by Al+ +, 
or, as it is now written, Al(im). The 16-fold Rydberg constant would, 
on the same theory, also be interpreted as meaning that the atoms of 
silicon which emitted this spectrum were those that had lost three 
electrons, i.e. Si(tv). These results, it will be seen, amply confirm 
the view that the bound electrons in the neutral atoms of sodium, Na(1), 
are of the same type and are characterised by the same quantum 
numbers as those of the singly ionised atom of magnesium, Mg(m), 
_ of the doubly-ionised atom of aluminium, Al(m1), and of the trebly- 
_ionised atom of silicon, Si(rv). 
What has been found to be true of the spectra of sodium, magnesium, 
| aluminium, and silicon, will no doubt be found to be true of the spectra 
- of the elements lithium, beryllium, boron, and carbon. The spectra 
_ of beryllium and boron are extremely meagre in wave-lengths, and but 
_ little is known of their spectral series. The spectrum of carbon, how- 
ever, especially in the extreme ultra-violet, has been well worked out 
: by a number of observers, and particularly so by Simeon.*° 
In the spectrum of beryllium the doublet A = 3131.194 A, 
A =3130.546 A has been shown to be the first member of a principal 
and a second subordinate series of doublets.- Moreover, Back,*' who 
recently investigated its magnetic resolution, has found that the mag- 
netic components are of the D, and D, type, just as Kent has shown 
the magnetic components of the close lithium doublet A= 6708 A 
to be. It will, therefore, probably be found when the spectrum of 
beryllizm has been extended that the doublet A = 3131.194 A, 
A =3180.546 A will prove to be the first member of the doublet series 
of the positive singly-charged atom of beryllium, with a Rydberg con- 
stant for the series of 4K. In the spectrum of boron the doublets 
4 =2497.73 A, }=2496.78 A and A =2089.49 A, A =2088.84 A, 
particularly the latter, merit attention in looking for a 9K series. In 
the ultra-violet spectrum of carbon there is a strong doublet at 
A =1335.66 A, } =1334.44 A, and another nearly as strong at 
A =1329.60 A,A=1329.07 A. These two also merit attention in any 
attempt to identify 16K series for this element. 
In considering the general validity of the Kossel-Sommerfeld Dis- 
‘placement Law the recent work of Catalan * on the series spectra of 
Manganese, chromium and molybdenum is of interest. 
_ The spectra of the neutral and singly ionised atoms of manganese, 
as well as that of the neutral atoms of chromium, have been shown 
by him to consist of sets of sharp diffuse and principal triplet series. 
Moreover, he has found that in all these spectra there are certain 
groups of prominent lines, to which the name ‘ multiplet’ has been 
given, that have similar characteristics, and that show similar varia- 
tions with changes in temperature. This has led Catalan to put forward 
pat i 
80 Simeon, Proc. Roy. Soc., A, vol. 102, p. 490, 1923. 
$1 Back, Ann. der Phys., No. 5, p. 333, 1923. 
_ *2 Catalan, Phil. Trans., Roy. Soc., Series A, vol. 223, pp. 127-178, 1922; 
).R., Jan. 8 and 22, and April 16, 1923. 
