RECENT ADVANCES IN SCIENCE 199 



Magnitudes of the Cape Photographic Durchmusterring, 

 No. 2, H.A., 80, No. 13. 



Harvard Standard Regions, H.A. 71, No. 4. 



Tucker, R. H., The Magnitude Equation and the Visual 

 Scale, Lick Obs. Bull. No. 307, 191 8. 



Halm, J., On the Determination of Photographic Magni- 

 tudes (second paper), M.N., R.A.S. 78, 379, 191 8. 



Miscellaneous. — Uhler, H. S., Generalisation of the Pro- 

 blem of the Rotation of Prisms Producing Constant Deviation 

 by two Refractions and one Internal Reflection, Aslroph. 

 Journ. 47, 65, 191 8. 



Dawson, B. H., Resultade de las observaciones con la 

 ecuatorial de 433 mm. de abertura (191 2-1 7), Pub. La 

 Plata Observatory , 4, Pt. i a . 



PHYSICS. By James Rice, M.A., University, Liverpool. 



Volume xxx. of the Proc. Phys. Soc. contains two interesting 

 papers by Prof. Nicholson. In Part I. (December 191 7) he 

 makes some tentative suggestions concerning the structure of 

 the electron and of the nucleus of an atom. There are several 

 difficulties which are at present encountered in discussing the 

 form of electrons. One is the existence of a finite radius and 

 therefore also a discontinuity at a prescribed surface which 

 marks off a distinct region from the ether. This conception is 

 somewhat at variance with the views of those who regard 

 the electron as a structure built out of ether ; but in the hands 

 of Lorentz and others it has been of great service, and has 

 led to conclusions concerning the variation of the mass of 

 an electron with its speed which are in undoubted agreement 

 with careful experiments. Such considerations involve the 

 existence of a linear constant which is the same for every 

 electron and is usually regarded as a " radius." Thus it 

 appears that if e is the fundamental electronic charge (in 

 electrostatic units), and a is the " radius " (in centimetres) 

 the mass of the electron is a multiple of e 2 /a, the multiple in- 

 creasing with speed, but for small speeds (i.e. small compared 

 to the speed of light) being equal to 2/3C 2 , where c cms. per 

 sec. is the speed of light. This result rests on the assump- 

 tion that all the charge of the electron is confined within a 

 sphere of radius a and is uniformly distributed therein. (No 



