PROCEEDINGS OF SECTION A. 319 



7.— ON THE VELOCITY OF EJECTIOxN OF THE ELECTRON 

 FROM AN IONISED MOLECULE. 



By R. B. KLEEMAN, £.Se., 1851 Exhibition Scholar of the University of Adelaide. 



[Abstract.] 



It has been shown by the author (Phil. Mag., Oct., 1906) that 

 initial recombination does not occur in the case of ions made by 8, 7, 

 or X rays, so that the effect is peculiar to the ions marfe by a rays. 

 In explanation, it is now suggested that the electron is ejected from the 

 atom with different speeds by these different ionising agents. Curie and 

 Sagnac have shown that the negative particles displaced from a metal 

 plate by X rays have considerable penetrating power, and it is to be 

 assumed that electrons ejected from gaseous molecules by the same rays 

 also move with large velocities. Thus they soon become well separated 

 from their parent molecules, and the phenomenon of initial recombina- 

 tion does not occur. On the other hand, Fiichtbauer (Phys. Zeit., Nov., 

 1906) has shown tiiat the secondary radiation due to canal rays has very 

 little penetrating power ; and it may be assumed, therefore, that this is 

 true also in the case of the a rays, which are so very similar to canal 

 rays. Hence the electron ejected by the a particle does not get away 

 from the influence of its parent atom, and is apt to recombine with it. 

 It is suggested that the electrons are ejected at slower speeds as the a 

 particle slows down, which may explain why the a particle, though it 

 produces more ions towards the end of its course, spends its energy at a 

 uniform rate as it goes. 



8.— AUSTRALIAN GEODESY. 



By W. ERNEST COOKE, M.A., F.R.A.S., Government Astronomer for 

 Western Australia. 



[Abstract.] 



Probably no problem in geodesy more urgently awaits solution 

 than the determination of the true shape of the earth ; and no place 

 is so well suited for this work as AustraUa, with its clear atmosphere, 

 immense plains, and the advantage of being under a single Government 

 which has control of all the telegraph lines. 



This compact little continent, of nearly 20° by 40° is pecuHarly 

 adapted for the latest geodetic methods, such as are now being used in 

 mid-Europe by the International Geodetic Bureau, and may be sum- 

 marised thus : — 



1. A careful triangulation is made of the prepared field of opera- 

 tions. 



2. Determinations of latitude and either azimuth or differences of 

 longitude are made by the most refined methods. 



3. Latitudes and longitudes of each principal astronomical station 

 are computed from the triangulation, on the assumption that the earth 

 has some definite figure — say, Clarke's or Bessel's ellipsoid. 



