314 SECTIONAL TRANSACTIONS.— A. 



Dr. S. M. Naud^. — The Quadruplet Structure of the Spark Spectrum of 



Mercury, Hg II. 



By means of a direct current discharge "with 1,600 volts in a tube ■which was 

 provided with a hollow carbon cylinder as cathode and contained mercury in the 

 presence of helium, Paschen has recently produced and analysed the ordinary spark 

 spectrum of mercury. By choosing a larger cathode and using 5,000 volts D.C., 

 it is possible to maintain a steady discharge in pure mercury vapour which is 

 continuously produced by the heat from the glowing cathode. The spectrum so produced 

 has been photographed with glass and quartz Hilger spectrographs, a one and a half 

 metre concave grating and a one-metre vacuum spectrograph. On the basis of the 

 (5d96s2)3D3 5 ground terms discovered by Paschen, twenty new terms have been 



found belonging to multiplets which have the quadruplet structure ; these are 

 compared with the copper arc spectrum. The terms obey the rules developed by 

 Pauli, Heisenberg and Hund. The excitation potentials of various lines calculated 

 from the term scheme, compare satisfactorily with measurements by direct impact 

 of electrons made by Dejardin. 



Prof. S. Chapman, F.R.S. — A Theory of the Equilibrium and Changes of 

 Atmospheric Ozone. 



Dr. F. W. Aston. F.K.S. — Recent Work on Mass Spectra. Followed by- 

 Discussion on Atomic Nuclei. — Sir Ernest Rutherford, O.M., 

 Pres. R.S. 



Thursday, August 1. 



Dr. EzER Griffiths, F.R.S. — Some Aspects of the Research Work of the 

 National Physical Laboratory, England. 



The paper describes with numerous illustrations recent research at the N.P.L. on 

 industrial problems and in the development of instruments. 



The purposes for which the Laboratory was founded were (1) to carry out research, 

 especially research required for the accurate determination of physical constants and 

 for the maintenance of standards ; (2) to make tests on instruments and materials ; 

 and (3) to carry out special investigations for Government Departments and private 

 firms. 



Whilst models are used for investigations in connection with the lighting of picture 

 galleries, the acoustics of public buildings, and the design of ships and aeroplanes, 

 especial attention is given to the translation of the data to full scale by actual observa- 

 tions on the full-sized structure and by theoretical work based on the Principle of 

 Similitude. 



In instrumental equipment the application of interferometer methods is illustrated 

 by apparatus for the testing of camera lenses and telescope objectives, block gauges 

 for length measurements and the mode of vibration of piezo-electric quartz oscillators. 



The methods employed for the establishment of the scale of temperature in the 

 range —200° to -f3000° C. and the determination of the electrical units are outlined. 



Mr. A. C. Menzies. — The Raman Effect : a Short General Account. 



Sir Gilbert Walker, F.R.S. — Meteorology in Application. 



Joint Discussion (Sections A, B) on Quantitative Chemical Analysis by 

 X-Rays and its Applications. — Prof. G. Hevesy. 



A method has been worked out by which minerals and alloys can be quantitatively 

 analysed without the use of chemical processes. A known amount of reference 

 substance is added to the substance to be investigated and the intensity of the 

 emission X-ray spectra of the two substances excited by X-rays is examined. In this 

 way practically any element in a mineral can be determined in a few hours, provided 

 the proportion present is more than one in ten thousand. The method is particularly 



