264 



Photograph VI is a trial'plate to investigate the effect of various times 

 of exposures. The exposures marked N are seen to be slightly darker 

 on the negative. This seems to indicat'^^ that there is a slight effect 

 from the radiations of the Welsbach burner. Photographs VII and VIII 



are to show whether or not VI is due to a radiation. VII shows similar 

 results to VI and is taken under similar conditions. It was thought 

 that it might be due to heat, and to prove this a lead plate was placed 

 against the tin can. where it became heated. Exposure VIII is made with 

 the radiation cut off by the lead plate suspended between the source and 

 sulphide screen and shows similar results to VI and VII. The exposures 



