﻿52 Dr. G. Green on Fluid Motion 



Evidence obtained from the Wilson photographs also leads 

 to the same idea, for it has been shown by Shimizu * that 

 the observed number of ray tracks which break up into two 

 branches near the end of the range is much greater than the 

 number deduced from probability considerations based on 

 our present theory of atomic structure. 



It is noteworthy that this anomalous behaviour of the 

 a particle occurs at low velocities, where practically no 

 investigation of the scattering of a particles has been carried 

 out on account of the experimental difficulties of dealing 

 with slow ol particles. It is at higher velocities, where the 

 theory of scattering put forward by Sir Ernest Rutherford 

 has been so fully verified by experiment, that the most of 

 the theoretical straggling takes place, and this straggling- 

 has apparently been accounted for. 



In conclusion I wish to express my best thands to Professor 

 Sir Ernest Rutherford for his kind interest and advice. 

 I also wish to thank Mr. Crowe for the preparation of the 

 radioactive sources. 



Y. On Fluid Motion relative to a Rotating Earth. By 

 George Green, F>.Sc, Lecturer in Natmal Philosophy in 

 the University of Glasgow f. 



THE subject of this paper is at present one of consider- 

 able interest to meteorologists. Papers by the late 

 Dr. Aitken and also by the late Lord Rayleigh on the 

 dynamics of cyclones and anticyclones have been followed 

 by more recent papers by Dr. Jeffreys, Sir Napier Shaw, 

 and others. Very few actual solutions of the equations 

 defining atmospheric motions have been obtained. In the 

 late Lord Rayleigh's paper % attention is drawn to certain 

 general hvdrodynamical principles relating to the properties 

 of rotating fluid which can be applied to " assist our judg- 

 ment when an exact analysis seems impracticable." The 

 importance of the theorem regarding the circulation of the 

 fluid in any closed circuit is clearly explained in its applica- 

 tion to any actual fluid motion. In applying this theorem 

 to fluid motion in the atmosphere, however, we must bear in 

 mind that the motions with which w r e are concerned are not 

 the actual motions of the particles in space but their motions 

 relative to the Earth itself at each point of observation. 



* Shimizu, Proc. Roy. Soc. xcix. p. 432 (1921). 

 f Communicated by the Author. 

 X Sc. Papers, vol. vi. p. 447. 



