i8 SCIENCE PROGRESS 



V. and J. Bjerknes with regard to rain of this kind. On 

 the plains the rain ceased, in the case described, with the arrival 

 of warm surface air, but a little orographical rain continued 

 to fall on the Norwegian mountains. 



The formation of cold-front and warm-front rain is similar 

 in summer and winter, but in summer the discontinuities of tem- 

 perature at the surface are often obscured by solar heating. 

 An example drawn from August 1919 is examined and, with 

 the help of the large-scale stream-line maps, the disturbing 

 effects of the various mountain ranges are traced. In this 

 particular cyclonic depression the " warm sector " was found 

 to diminish from day to day and soon disappeared. This led 

 to the dispersal of the whole system, as is usual under such 

 circumstances. 



Local Showers. — In dealing with this part of the subject the 

 close network of stations and construction of lines of flow are 

 seen to be essential. For the production of these summer 

 showers not only is convergence of the air-streams necessary, 

 but also sufficient humidity. The latter is derived from the 

 system of sea breezes, which play a fundamental part in the 

 process. In one of the examples given the gradual invasion 

 of Norway by polar air of low humidity entirely stopped a 

 period of local showers. It is very evident throughout that 

 the differences of pressure (always slight during this type of 

 weather) play an insignificant part in comparison with the 

 stability and moisture-content of the air. 



BIBLIOGRAPHY 



GuiLBERT, G., Sur Tobservation des nuages en provision du temps, Compies 



Rendus, tome 174, 1922, pp. 817-20. 

 Humphreys, W. J., Fogs and Clouds, Journal Frank. Inst., vol, 192, 1922, 



pp. 217-30, 327-84. 

 KoHLER, HiLDiNG, Ubet die Tropfchengrossen der Wolken und die Kondensa- 



tion, Met. Zeit., 38, 1921, pp. 359-65. 

 MoHOROVicic, S., Die zweiundeinhalt Jahrhundert lange Periode der Erde- 



ben-und Klimasschwankungen, Met. Zeit., 38, 1921, pp. 373-5. 

 Bjerknes, J., On the Dynamics of the Circular Vortex, with Applications to 



the Atmosphere and Atmospheric Vortex and Wave Motions, Geophys. 



Pub., vol. ii, No. 4, p. 87. 



PHYSICS. By J. Rice, M.A., University of Liverpool. 



The Problems of Atomic Structure. — In the previous issue of 

 Science Progress reference was made in this section to recent 

 work by Sir Ernest Rutherford and his pupils and its relation 

 to one of the problems of atomic structure, viz. the charge on 

 the nucleus or, what comes to the same thing, the number of 

 electrons in its " planetary" system. It appears definitely to 

 confirm the conclusion derived from other sources of evidence 



