THE PHENOMENA OF ELECTROSTATICS. 



237 



obtained by the arrangement shown in Fig. 166 in which AB is 

 a sensitive photographic plate upon which the narrow stream of 



photographic plate 



B 



f(~ 



t-f-wave 



^radio-active 

 material' 



Fig. 165. 



Fig. 166. 



rays impinges. Figure 167 shows the effect of an electrical field 

 upon a thin -stream of rays from a radio-active substance. The 

 direction of the electric field is shown by the fine horizontal arrows 



photographic plate* 



tlecbicallj/ 

 charged 

 plate + 



(positive) , 



electrically 



charged 

 i plate 



'(negative) 



~s//fi///r////////////. 



lead block / 



j////////////////////, 



7. lead block 



^ >^^fc,. 



^active material 



Fig. 167. 



(the lines of force of the electric field pass from the positively 

 charged plate to the negatively charged plate). The effect of the 



