On the Photographic Action of a, ß and 7 Rays emitted from Eadioae-tive Substanoes. \~i 



In conclusion, we wish to thank Professor Nagaoka for pla- 

 cing the resources of the Laboratory at our disposal and for his 

 continual interest ^luring the progress of this investigation. 



Pli_ysical Laborator}^, University of Tokyo. 



Explanation of llie Piales. 



Fig. 1. The general feature of a plate coutaiuiug several spots, cacb of wbic-li consists 



(^f a nnnil)er of radial a ray tracks. The isolated spot at the top and the 



large one at the bottom of the figure are reproduced in figs. 5 and G 



respectively in a higher maguiiication. 

 Figs. 2-4. Haloes due to radium C, at different stages of formation, 

 Figs. 5-8. Haloes (hie to radium A and C. In eacli halo two concentric circles are 



to be seen. Tiie inner circle is due to radium A and the outei' to radium C. 



In fig. 5 the inner circle is more conspicuous than the outer one, while m fig. 



(> the reverse is the case. 

 Fig. 9. The tracks of a particles emitted from a nucleus of radium C, reaching to 



varioiis distances. 

 Fig. 10. a ray tracks showing sudden bents. On tliis figure are visible the tracks of 



four a particles which passed from left to right. Three of tliem suffered 



sudden deHxions. 



Published November 20Lh, 1917. 



