940 Mr. A. G, Shenstone : Attempt to detect Induced 



the screen. This distance in practice was 1*2 cm. Actually 

 with the arrangement of distances such as is shown in the 

 diagram a few hydrogens could reach the screen. With 

 aluminium they were observed about 1 in 6 or 7 minutes 

 whether the disk was running or stationary.. To avoid 

 vibration the ZnS screen was mounted on a very stiff 

 attachment on the microscope objective, and remained in 

 perfect focus even when the vibration was at its worst. 



Fig. 1. 



Bearings of Disc. 



Mica = /c/77. a/r. 

 "~-\ / Source. 

 ! / / A//c/re/ Stee/ D/sc. 



lead <4/?y/e\ 



fio/d/'ng 

 source. 



Screwed to-, 

 frame work [p^ 

 of D/sc. 



Zn S Scree/?. 



Microscope 

 Objective* 



Ho/der 

 for Source. 



APPARATUS FOR I H V ESTI GATI O fl OF 

 inDUCED RADIO- ACXI ViTY. 



Lead Bracket. 



Difficulty was had at first from the wind from the disk 

 blowing the crystals off the screen, but this was satisfactorily 

 overcome by covering the screen with aluminium foil except 

 for a hole over the portion included in the field of the 

 microscope. The microscope used was fitted with Watson's 

 " Holos" X 5 eyepiece and Holos objective of *45 n.a. and 

 16 mm. focal length. A rim of the substance under exami- 

 nation was stuck on to the face of the wheel with shellac, 

 which successfully withstood the huge centrifugal force 



