FIRST RESEARCHES IN PHYSICS 47 



year, that Bose felt free enough definitely to start regular 

 work as an investigator; indeed on that birthday, Indian 

 fashion, he made to himself that vow. And, as we have 

 seen, he was well prepared, not only in physical knowledge 

 and experimental skill, but also in character, his initial 

 adventurous courage and strenuousness now matured and 

 strengthened by life. 



In these years the most conspicuously interesting move- 

 ment in physics centred round the work of Hertz, the 

 brilliant and too short-lived experimentalist who produced 

 the electric waves which Clerk Maxwell, building in his 

 turn on the experimental work of Faraday, had predicted 

 mathematically, twenty years before, in his magnificent 

 correlation of light-waves with electro-magnetic disturbance. 

 So in the formative years of our investigator, as older readers 

 will remember, the Hertzian waves were the wonder of their 

 time, just as later the X-rays of Rontgen, and a little later 

 the magical radium of Madame Curie, and the later develop- 

 ments of that still branching investigation. 



First, then, a word of explanation is needed before we 

 come to Hertz and his problem, much less to Bose's develop- 

 ment of it. In the previous generation Fresnel had cleared 

 the wave-theory of light, and enabled us to visualise it, in 

 terms of vibrations of the ether : but these not in longitudinal 

 pulsations like sound-waves in air, but transversal, like 

 the up and down movements which take place in the waves 

 of the sea, which travel fast and far without corresponding 

 movement of the water itself until it breaks upon the beach. 

 Throw a stone into a standing pool ; and watch the surface 

 rising and falling as the wave-circles extend to the bank ; 

 watch too how this reflects these wave-circles back into the 

 pond, and at angles varying with those of their incidence ; 

 and thus, in the minor infinities of intersecting ripples which 

 arise, we have a simple introduction to those intricate yet 

 orderly wave-motions of the ether which the physicist has 

 to assume as filling space, in order to realise the manifold 



