Colli 



of a Particles ivith Light Atoms. 



563 



This carrier was then introduced into the rectangular brass 

 vessel shown in fig. 1 of the previous paper, and the whole 

 apparatus was phiced between the poles of a strong electro- 

 magnet. A vertical slit 1*5 cm. long and 3 mm. wide, cut in 



Fiff. 1. 



the end plate ol the box, was covered with a thin sheet of 

 iron E whose stopping-power for a particles corresponded to 

 4 cm. of air. Close to this was placed the zinc sulphide 

 screen S. The distance between the slits A and B was 

 2*85 cm., and between B and the iron screen 3*25 cm. On 

 exhausting the apparatus of air a well-defined band of a. rays 

 about 2 mm. broad was observed on the screen. The distance 

 measured by the microscope between the centres of the two 

 bands on reversing the field of about 9000 gauss was about 

 3*9 mm. A film of paraffin wax about 30 fju thick mounted on 

 a frame was then placed close to the slit A between it and the 

 source. This gave a band of H scintillations on the screen, 

 which was of about the same width as the beam of a rays. 

 Aluminium screens were introduced between the iron plate 

 and zinc sulphide screen, so that the total absorption between 

 the source and screen was equivalent to 14*4 cm. of air. 

 Under these conditions the two bands of H scintillations 

 obtained by reversal of the field were carefully determined 

 by the microscope, and the centres of the bands were found 

 to be about 6 mm. apart. 



As a result of three concordant determinations, it was 

 found that under the experimental conditions the average 

 deflexion of the pencil of H atoms was 1*45 times the 



