Experiments on Positive Rays. 235 



a positive charge by subsequently colliding with cathode 

 rays ? The evidence at present before us points to the con- 

 clusion that an overwhelming majority of these charged 

 atoms have positive charges, i. e. have lost a corpuscle: has 

 this corpuscle been detached by the impact with a positive 

 particle which set the atom free ? To force a corpuscle from 

 an atom would seem to require the communication to the 

 corpuscle of an amount of energy equivalent to that possessed 

 by the corpuscle when it has a velocity comparable with 

 2 x 10 8 cm. /sec. It is difficult to see how a comparatively 

 slowly moving heavy atom could communicate so great a 

 velocity to the corpuscle directly. Tt might, however, liberate 

 a corpuscle which was previously moving with this velocity 

 in a state of steady motion round a massive system. Take, 

 for example, the following case : Suppose a corpuscle were 

 moving in a state of steady motion round an electrical doublet 

 AB, fig. 19, having a mass comparable with that of an atom ; 



Fig. 19. 



<izr> 



— I B 



suppose, now, that the doublet were struck by an atom and 

 knocked into a position A'B' at right angles to AB. The 

 Corpuscle would fly off with the velocity it had before the 

 impact with the doublet : and it is easy to show that the 

 work required to turn the doublet from AB to A'B' is equal 

 to the energy with which the corpuscle flies off. We see 

 that in some such way as this a slowly moving atom with the 

 requisite energy might detach a corpuscle from an atom. 



Atoms with double charges. — The photographs show that 

 the atoms of nearly all the elements, with the very suggestive 

 exception of hydrogen, occur w T ith two charges, though the 

 number of these doubly charged atoms is always small 

 compared with those having a single charge. We are able 

 to detect the double charge on the atom because the parabola 

 corresponding to the doubly charged atom is distinct from 

 that due to the singly charged atom or molecule. We could 



