PROFESSOR SIR J. J. THOMSON 



Experimental discoverer of the electronic constitution of matter, in the Cavendish Physical Laboratory, Cambridge. A great investi- 

 gator, noted for the imaginative range of his hypotheses and his fertility in experimental devices. 



From the Smithsonian Report, 1915. 



ELECTRONS PRODUCED BY PASSAGE OF X-RAYS THROUGH AIR 

 A photograph clearly showing that electrons are definite entities. As electron* 

 leave atoms they may traverse matter or pass through the air in a straight path 

 The illustration shows the tortuous path of electrons resulting fr. 

 atoms. 



