eee LL eee 
SECTIONAL TRANSACTIONS.—A. 431 
Proresson Mitiikan forwarded a summary of the results obtained to date 
by various investigations on the extreme ultra-violet spectra of the elements. 
_Prorressor Fowzer dealt with optical spectra. Alternation of doublet and 
triplet series in the spectra of elements of successive groups in the periodic 
classification. General relations between the spectra of the elements of the 
same group, and departure from these relations in the case of some of the lighter 
elements. Remarks on the spectra of the lighter elements for which series 
have not yet been traced. The spectra of ionised elements; the displacement 
law. The spectra of certain elements, including silicon, at successively higher 
stages of ionisation. General accordance of the phenomena with Bohr’s theory. 
21. Dr. D. Coster.—On High Frequency Spectra and the Theory of 
Atomic Structure. 
Moseley showed that the characteristic X-ray spectra have a very simple 
structure. The square root of the frequency of a given X-ray line is a linear 
function of the atomic number. The great changes in physical and chemical 
properties, which mostly occur when proceeding from one element to the next 
one in the periodic table, are not expressed in the X-ray spectrum. 
Recent researches have revealed that some peculiarities of the periodic table 
find expression in the X-ray spectrum. If we plot Moseley curves not for the 
lines themselves but for the spectral terms,! we observe at different stages 
sudden changes in the slope of these curves. These irregularities correspond 
with regions of the periodic table where, according to Bohr, an inner group of 
electrons is being completed—i.e. in the neighbourhood of the iron group, the 
palladium group, the platinum group, and in the case of the rare earth metals. 
Recently X-ray spectroscopy has led also in a more direct way to a confirma- 
tion of the Bohr theory. According to Bohr, the element of atomic number 72 
should not belong to the rare earth metals, but must be a homologue of 
. This conclusion of the theory was verified by the discovery of 
afnium. 
22. Dr. F. W. Aston, F.R.S.—Further Determinations of the Con- 
stitution of the Elements by the method of Accelerated Anode 
Rays. 
23. Mr. R. W. Rosertrs.—The Magnetic Rotary Dispersion in 
certain Paramagnetic Liquids. 
It is well known that the presence of iron salts in aqueous solution will 
cause a diminution of the magnetic rotation of the solvent. It was found 
by Richardson, Roberts, and Smith that the same is true for cobalt salts at 
ultra-violet frequencies, but not for nickel salts. As the effect shown by 
cobalt salts might be a dispersive one, the ordinary dispersion of aqueous 
solutions of several cobalt salts in the visible and ultra-violet portions of the 
spectrum has been investigated. The results obtained show that the depression 
in the magnetic rotation exhibited by aqueous solutions of cobalt salts is a 
true paramagnetic one superimposed on the usual positive rotation explained 
by the Hall effect. 
24. Mr. RB. Asierr.—The Angle of Contact—Variation with Relative 
Motion of Solid and Liquid. 
When a cylinder with its axis horizontal is partially immersed in a liquid 
to such a depth that the liquid surface is horizontal right up to the cylindrical 
surface, then the tangent at the line of contact makes an angle with the 
horizontal equal to the angle of contact §. This has been found to be 
104°34'+5’ for paraffin wax and water at 10°C. On rotating the cylinder 
uniformly the angle on the side emerging decreases towards a minimum value 
1 Every line frequency may be represented by the difference of two terms, 
each of which, corresponds with, the energy of the atom in one of its stationary 
states. j 
1923, GG 
