Scattering of u Particles by Gases, 291 



the experiments are being continued both with gases and 

 metal foils with thorium active deposit as the source of 

 a particles, though it must be stated that, owing to lack of 

 intensity, thorium active deposit did not give very encouraging 

 results with gases in some preliminary experiments carried 

 out at Manchester. With the heavier metal foils, however, 

 they will probably give even more satisfactory results than 

 those obtained by Geiger by the scintillation method. 



Description of Apparatus used. 



Figs. 1 and 2 will explain the arrangement of apparatus 

 as finally adopted. C C is the gas-chamber shown in fig. 2. 

 The gns chamber is connected by (fig. 1) a glass tube with a 

 Toepier pump at T, a Fleuss pump at F, a manometer at M, 



Fig. 1. 



a small flask containing P 2 5 at X, and a side-tube at N 

 communicating with a series of drying-tubes through which 

 any particular gas can be admitted into the gas-chamber. 

 At L is a ground-glass joint where the gas- chamber can be 

 readily connected lo or detached from ihe r< st of the 

 apparatus. The gas-chamber is placed between the poles of 

 an electromagnet to deflect /S rays. 



