756 Dr. Bottomley and Mr. King : Experiments with 



appear to stop, or, at any rate, to reduce greatly the 

 radiations which affect the gold leaves. Some carious 

 observations, however, which may modify this last statement, 

 were made when the radium clock was the subject o£ experi- 

 ment. It was found that metal screens allowed radiations to 

 pass through, which repelled the gold leaves of the radium 

 clock, and thus caused its period of charge and discharge to 

 be lengthened. Tables showing this numerically will be 

 given in a future communication. 



Experiment 10. — It was found that divergence of the 

 leaves only took place when the light was shining directly 

 upon them ; and that no effect was perceptible when the light 

 was projected through the glass envelope, without illuminating 

 the gold leaves. In testing this, the image of an incandescent 

 electric lamp was focussed, by means of a lens, first upon the 

 gold leaves and then upon the glass cover, the gold leaves 

 being avoided. The result mentioned above was obtained; 

 but it was also found that if only one leaf was illuminated 

 the opposite leaf was repelled away from the illuminated one, 

 which remained hanging vertically, as shown in fig. 6. If the 



Fig. 7. 



■«( 



spot of light was so arranged that it illuminated a little 

 patch in the centre of one of the gold leaves, the opposite 



