Atomic Nucleus and the Law of Force. 



m 



reaching the zinc-sulphide screen. The position of: A was 

 adjusted to be equidistant from the source R and the 

 zinc-sulphide screen S. The distance from the source to 

 tin- diaphragm was 29*1 mm. and from the source to the 



Fig. 12. 



screen 99*2 mm. The source-holder, diaphragm, and foil- 

 holder were mounted on a brass base which fitted into slides 

 in the brass box 13, 12 cm. x 6 cm. x 6 cm., and were adjusted 

 so that their common axis was exactly central to the 

 opening in the end of the box. This opening, of 6 mm. 

 diameter, was covered with a mica sheet of 2 cm. stopping- 

 power. The box was closed by the glass plate C and could 

 be exhausted through the tap T. 



The direct pencil of a rays which came through holes in 

 the central disks of D and A could be cut off at will by the 

 lead screen L carried by the glass joint G. 



The ZnS screen was observed through the microscope M, 

 which had a field of view of 1*5 mm. diameter. 



The wheel, which was made of glass, was rotated between 

 the end of the box and the ZnS screen, and contained 

 besides the slit a hole 1 cm. in diameter, which was brought 

 between the opening and the screen when counting the 

 scattered particles. When the wheel was rotated for 

 the counting of the direct pencil, this hole was covered 

 with a thick sheet of mica. The diameter of the wheel at 



