386 SECTIONAL TRANSACTIONS.— A. 



(concurrently with above.) 

 Symposium on Magnetic alloys and X-ray structure (continued) (2.15). 



Dr. W. SuCKSMiTH. — The variation of magnetic saturation intensities 

 with temperature in the iron-nickel- aluminium system. 



In view of the necessity for making measurements on a large number of 

 alloys of widely varying physical properties, a new method of measuring the 

 saturation intensity (in fields up to 18,000 gauss) from liquid air temperatures 

 up to the Curie temperature, has been developed. The method requires 

 only about aV^h gram of the alloy, and is not dependent upon the shape of 

 the specimen. The measurements are equally valid for materials ranging 

 from coarse powders to roughly cut cylinders. 



Measurements have been made on alloys of which the X-ray structure 

 has been investigated by Bradley and Taylor, the same specimens having 

 been utilised through the collaboration of Dr. Bradley. 



Some of the multiphase regions have been investigated, and the results 

 show that the phase boundaries as determined by magnetic methods con- 

 form closely to those given by the X-ray data. The different regions usually 

 have characteristic properties, and the effect of heat treatment upon struc- 

 ture changes can be followed quite closely by observation of the magnetic 

 saturation intensity at different temperatures. 



Mr, D. A. Oliver. — Martensitic permanent magnet steels and dis- 

 persion-hardening alloys (2.45). 



The structures of martensitic permanent magnet steels and dispersion- 

 hardening alloys are illustrated by a selection of photomicrographs. The 

 necessity for X-ray examination is stressed. A summary of the important 

 magnetic properties is given with special reference to those alloys which are 

 of commercial importance. The effect of impurities on magnetic proper- 

 ties is discussed and recent data on the effect of carbon presented. Mention 

 is also made of the improved magnetic properties which can be obtained 

 when these magnetically hard alloys are cooled in a magnetic field. A few 

 experiments are carried out illustrating either the properties or the applica- 

 tions of the newer permanent magnet alloys. 



General Discussion (3.15). 



Visit to works of Cambridge Instrument Company. 



Saturday, August 20. 



Symposium on High-altitude cosmic radiation (lo.o). 



Prof. P. M. S. Blackett, F.R.S. — Introduction. 



Prof. W. H. Furry. — A discussion of some recent experiments on the 

 properties of cosmic ray particles (10.45). 



It is now realised that most cosmic ray showers can be explained by the 

 assumption that electrons multiply by radiative collisions and pair produc- 

 tion as required by the present radiation theory. The most conclusive 

 evidence comes from cloud chamber photographs obtained by Fussell. 



