SECTIONAL TRANSACTIONS— A. 341 



Absorption lines are supposed to be produced by combined scattering 

 and absorption, the former process being predominant in the upper layers 

 and being responsible for the bright lines in the chromosphere. The 

 behaviour of absorption lines at the extreme limb is not fully accounted 

 for by current theory. Lines represented strongly in the flash spectrum 

 can be seen bright over the edge of the photosphere ; numerous absorption 

 lines due to neutral metals can be detected at the extreme limb, but excitation 

 potential is an untrustworthy guide to their strength. There is an un- 

 explained shift to the red of the absorption lines relative to the chromo- 

 spheric lines. 



Dr. R. L. Waterfield. — Coronagraphy (12.45). Read by Prof. W. H. 

 McCrea. 



Afternoon. 



Visits to Stanton Ironworks ; Bar-Lock Factory ; Messrs. John 

 Taylor & Co., Bell Founders, Loughborough ; North Wilford Power 

 Station. 



Tuesday, September 7. 



Dr. EzER Griffiths, F.R.S., and Mr. J. H. Awbery. — The contributions 

 of refrigeration to everyday life (lo.o). 



A review is given of some recent investigations at the National Physical 

 Laboratory and elsewhere which may be regarded as contributing to the 

 comfort and convenience of everyday life. 



They include : — 

 , (i) Work on basic engineering problems of refrigeration. 



(2) Investigations in hygrometry which find application in methods of 



' air-conditioning.' 



(3) Study of materials for thermal insulation. 



Film illustrating Industrial physics at the Natio7ial Physical Laboratory 

 (10.20). 



Prof. L. F. Bates. — The magnetic properties of amalgams (11. 10). 



The results of an examination of the magnetic properties of dilute amalgams 

 of metals with mercury, produced by electrolysis or by mechanical means, 

 are described. The dependence of the magnetic susceptibility at room 

 temperatures upon the concentration of the dissolved metal, and the variation 

 with temperature of the susceptibility of particular amalgams are discussed. 

 Experiments with iron amalgams are described. 



Mr. A. Brookes. — Some gas-absorption problems during annealing of low 

 carbon iron (11.25). 



Modernisation of a particular heat treatment department, replacing the 

 old coke-fired furnaces by electric furnaces having automatic control and 

 inert gas annealing resulted in the magnetic properties of the low carbon 

 iron being appreciably inferior to those given by the older methods, and. 



