X-RAYS AND CRYSTALS 389 



each direction being the axis of a cone which cuts the plate in 

 one of the ellipses. 



There can be no doubt that these crystallographs must throw 

 a great deal of light on the physical nature of these short ether 

 waves. When an electron is shot into the anticathode of the 

 X-ray bulb and then brought up, there must be set up those 

 electro-magnetic pulses first supposed by Stokes to constitute 

 X-rays. It seems very probable that the waves here dealt with 

 are these electro-magnetic pulses and it will be of the greatest 

 interest to discover whether they are the same as the X-rays or 

 not. All that is known of them so far is that they are penetrat- 

 ing and act on a photographic plate. It is possible that there 

 may be in the rays from an X-ray bulb two components, waves 

 and corpuscles. The electro-magnetic pulses can be regularly 

 reflected, can interfere, can act on a photographic plate and 

 perhaps can be polarised. Their energy is spread uniformly 

 over a wave front. On the other hand, the facts of the emission 

 of characteristic secondary radiation from metals, of the equality 

 of the speed of electrons knocked out of atoms by X-rays and 

 the speed of the electrons which originally produced the rays in 

 the X-ray tube, seem to be explained far more simply by suppos- 

 ing the existence of a corpuscular radiation. These corpuscles 

 are represented by quanta of energy flying through space con- 

 tained in a small region of invariable volume. There is perhaps 

 the possibility of both these components having been hitherto 

 classed together as one. This is only conjecture but at any rate 

 it seems as if these experiments of Laue and his collaborators 

 may solve not only problems of crystal structure but also the 

 problem of the true nature of X-rays. 



