— Se 
’ SECTIONAL TRANSACTIONS.—A. 368 
that they force their way into the continent in high latitudes and actually pre- 
vent the formation of anticyclones and their concomitant low temperature. These 
conditions lead to mild winters in Canada. : 
The Meteorological Service is investigating as to whether there is any 
connection between the temperature and position of the Japan current and the 
behaviour of these cyclonic areas. 
14, Prof. A. H. Compron.—The Quantum Theory of the Scattering of 
X-rays. 
15. Prof. J. A. Gray.—Scattering of X- and Gamma-rays and the 
Production of Tertiary X-rays. 
1. Experiments with X-rays show that the proportion of scattered rays of 
longer wave-length than the primary is independent of the crystalline structure 
and thickness of the radiator. 
2. The rather peculiar intensity distribution curves of unmodified and 
modified scattered radiations suggest that they are not really independent types. 
3. Results on the scattering of y-rays do not altogether agree with the 
quantum theory of scattering. 
4. The ‘tertiary’ X-rays discovered by Clark and Duane must be formed 
in the atoms in which the photoelectrons are produced. They may even be a 
special type of scattered rays. 
5. If X-rays consist of quanta, they should have a range. [If this is the 
case, in the writer’s opinion the wave theory should be abandoned. ] 
6. The writer, while aware of the difficulty of explaining certain results by 
the wave theory, believes that other results cannot be explained without its 
aid. The quantum theory cannot explain interference. 
16. Prof. W. Duanz.—On Secondary and Tertiary Radiation. 
This paper gives the results of recent experiments on secondary and tertiary 
radiation carried on in our laboratory by Doctors Allison, Clark, and Stifler. 
The experiments with an X-ray tube in one large room radiating through a hole 
in the wall into a second room that contains the X-ray spectrometer indicate 
the presence of scattered radiation, fluorescent radiation, and tertiary radiation 
only, in the beam of X-rays coming from a secondary radiator. The tertiary 
radiation has the short wave-length limit that would be expected if it were 
due to the bombardment of photo-electrons. No other radiation comparable in 
intensity with these three types appears in the spectra. In case the X-ray tube 
lies in a small box, the influence of the walls of the box on the spectra is 
discussed. 
Experiments also are described illustrating the reflection by a crystal of 
X-rays characteristic of the chemical elements in the crystal itself, and the 
precautions necessary to procure photographic evidence of this characteristic 
reflection are mentioned. 
By placing sheets of copper in the path of the X-rays incident on the crystal 
sufficient in thickness to cut off practically all the radiation having wave- 
lengths of the characteristic line spectra of the crystal, it has been shown that 
this phenomenon cannot be regarded as an increase in the reflecting power of 
the crystal for certain rays already existing in the primary beam, but must be 
due to the fluorescent radiation generated in the crystal itself by X-rays of 
much shorter wave-lengths. 
17. Prof. J. C. McLennan, F.R.S.—Recent Developments in Low 
Temperature Research. 
(A visit to the Cryogenic Laboratory, by kind invitation of Prof. 
McLennan, was paid during the meeting. Liquid helium and 
the luminescence of solid nitrogen, among other things, were 
exhibited. ) 
18. Joint Discussion with Section G on Optical Determination of 
Stress. 
