74 LIFE AND WORK OF SIR JAGADIS C. BOSE 



action of warmth helped the automatic recovery. Even 

 substances like iron, which remained conducting as an after- 

 effect of electric stimulus, recovered automatically when 

 maintained at a higher temperature. 



FIG. i. Periodicity of Electric Touch. Abscissa represents the atomic 

 weight ; ordinate the electric touch positive or negative. 



From the observations of these various characteristics, 

 Bose was led to suppose that electric radiation produced a 

 molecular change of an * allotropic ' nature, similar to the 

 allotropic change induced in sulphur or phosphorus by 

 visible light. 



The action of light on various kinds of matter is 

 familiarly known, though little understood. Everyone has 

 noticed how colours are often faded by exposure ; while 

 chemists have long known that common yellow phosphorus 



