SECTIONAL TRANSACTIONS.— A; 297 



An attempt is being made to get band spectra of these molecules by investigating 

 different sources of light containing various compounds of these atoms. So far bands 

 definitely ascribed to these molecules have not yet been found. The investigation 

 is being continued also on account of the knowledge such molecules would yield 

 about the nuclear structure of these atoms. 



(k) Mr. J. H. Lees. — A Self-recording Photographic Photometer. 



A Cambridge Instrument Co. non-recording photometer was adapted, using the 

 original photographic plate movement, the light source, and the slit sj'stem . To obtain 

 an accurate magnification of the plate motion, a fine steel wire wrapped round the 

 screw controlling it passes over the drum carrying the bromide paper, giving in this 

 instance a magnification of 20. 



The light passing through the plate falls on a General Electric Co. caesium on 

 copper vacuum photoelectric cell. The current from this is amplified by a Phillip's 

 electrometer triode, and finallj' a galvanometer reflects a spot of light on to the 

 bromide paper. 



{/) Jlr. W. R. Harper. — The Probability of modified X-ray Scattering. 



By the choice of a suitable wave-length the ionisation due to the passage of X-rays 

 through light gases is caused almost entirely by recoil electrons if the usual laws of 

 photoelectric absorption can be extrapolated to this region. An experiment is being 

 made to verify this and to measure the energy associated with the recoil electrons. 

 Hence, the probability of the occurrence of modified scattering may be compared with 

 theory, and further development should enable the method to be used for X-ray 

 intensity measurements. 



(jn) Dr. H. H. PoTTER.^(So»ie Experiments on Magnetic Alloys. 



A ternary alloy possessing pronounced ferromagnetism has been prepared by 

 melting together silver, manganese and aluminium. A maximum magnetisability is 

 obtained when the atomic proportions are four parts silver, one part manganese and 

 one part aluminium. 



An attempt is now being made to obtain single crystals of this alloy — ^which has 

 a face-centred cubic structure — with the object of studying the directional magnetic 

 properties. 



The system silver-manganese-tin has also been examined but shows no maximum 

 of magnetisability in the ternary system. The manganese-tin binary system, however, 

 contains two ferromagnetic compounds, one of them being strongly magnetic at low 

 temperatures. 



(n) Dr. G. I. Harper. — The Absorption of X-rays in the Region of 

 1 to 10 A. 



Hitherto the chief errors in such measurements have arisen from the difficulty of 

 obtaining thin films of sufficient uniformity and puritj'. These difficulties are being 

 avoided by the use of gaseous absorbers, the absorption coefficients being measured 

 by an ionisation method using a vacuum monochromator, and a PhiUip's Electrometer 

 Triode which has been adapted to measure ionisation currents down to 10"'^ amp. 

 with an accuracy of 1 per cent., the ionisation currents being recorded on a table 

 galvanometer. It is hoped that these measurements will serve as an accurate test 

 of the validity of Jonsson's law of absorption, which is not in agreement with later 

 measurements. 



(o) Mr. J. H. Burrow. — Demonstration of Glass Metal Seals and Glass- 

 bloiver's Lathe. 



