Rays of Positive Electricity. 757 



positions of the bands when the magnetic and electric fields 

 coincide, the continuous lines their position when the magnetic 



Fie:. 5. 







field is pushed forward towards the screen. The shape of the 

 lower band can be explained as we have seen by supposing 

 that it is due to secondary rays which are continually being 

 produced as the undetected rays travel from the cathode to 

 the screen. The configuration of the upper band can be 

 explained by supposing that it is due to primary rays coming- 

 through the cathode, and that these are not recruited b} r 

 secondary rays, but on the other hand gradually get 

 neutralized by combining with negative corpuscles. For if 

 this were the case the rays which strike the screen near are 

 not, as in the previous case, rays which have been produced 

 near the ends of the electric and magnetic fields, but are rays 

 which have been neutralized soon after entering these fields. 

 As the deflexions of such rays are due to the forces which act 

 on the charged particle immediately after it leaves the tube 

 and enters the space between the plates, the effect of pushing 

 the magnetic field forward away from the tube will be to 

 diminish the magnetic force on these particles while the 

 electric force is unaltered : this will clearly tend to make the 

 luminous band more nearly horizontal than it was before 

 the magnets were pushed forward, and we see from fig. 5 that 

 this is just the effect produced. 



The upper band also differs from the lower one in not 

 having, so far as I have been able to observe, any negative 

 portion connected with it. 



The difference between the properties of the rays which 

 constitute the two bands is also shown by the following 

 experiment. Two systems of magnets and parallel plates 

 instead of one are placed between the cathode and the screen, 

 the fields in these could be excited separately. The deflexion 

 due to the magnet next the cathode is horizontal, that due to 

 the magnet next the screen vertical. The electric fields are 

 at right angles to the corresponding magnetic fields. Suppose 

 that the magnetic field nearest the cathode is excited, the 

 phosphorescent patch will be drawn out into a horizontal 



