8 Proceedings of the Royal Irish Academy. 



volume of water gave a marked effect, so that the total activity obtained by 

 the use of acetone greatly exceeds that of the water solutions. 



4. The action of oxidizing agents greatly increases the activity of the 

 water solutions described above, and a similar effect was obtained by adding 

 oxidizing agents to solutions of several organic substances. Very large 

 activities were obtained in this way. 



These experiments seem to afford ample proof that, in these particular 

 cases at any rate, the emission of electrons under the action of ultra-violet 

 light is facilitated by chemical change. 



It is hoped to investigate some of the points raised in this paper in a more 

 conclusive manner, when we are in a position to use light of definite wave- 

 length. 



