224 Mr Orange, On certain phenomena of the kathode region. 



It would seem now that no such simple explanation based on 

 the geometry of the kathode will suffice. Each beam is sym- 

 metrical about the central normal to the corresponding side of the 

 triangle, although the two corners which bound that side differ 

 considerably. Thus we cannot invoke the aid of the electrostatic 

 field ; this is shown also by the way in which the two narrower 

 beams cross each other, at a of Fig. 3, as if operated quite inde- 

 pendently. The latter fact is also opposed to the supposition that 





Fig. 5. 



the constituent particles of the beams are strongly mutually 

 repulsive, a supposition that might have been advanced to account 

 for the curved boundaries. 



The author puts forward the suggestion that the latter are 

 similar to caustic curves, that is, are the envelopes of straight rays, 

 as shown diagrammatically in Fig. 5. 



We thus avoid the necessity for supposing the beams to be 

 acted on by peculiar systems of forces, systems which would seem 



