58 LIFE AND WORK OF SIR JAGADIS C. BOSE 



which stands conveniently upon one end of a writing-table, 

 and may be packed into a suit-case, and thus carried and 

 exhibited to any audience. 



Bose had now made himself the best equipped among 

 physicists in this field of investigation. For with the 

 most perfect production of rays, and these under the fullest 

 control, it was possible to work towards shorter and shorter 

 waves, less dispersive in their diffraction, and producible 

 as a definite beam of half -inch section. Furthermore, his 

 receiver not only surpassed previous ones in that sensibility 

 which is so great in all forms, but what is more important 

 in its certainty and uniformity of action. His problem 

 thus admitted of fuller and clearer statement, and*came 

 substantially to this : Hertz's study of the electric waves, 

 and still more his comparisons of their behaviour with 

 optical phenomena, were more or less qualitative. But 

 ' science is measurement ' : it must have quantitative 

 precision ; and for this purpose more regular waves must 

 be produced, and as near those of heat and light as 

 may be i.e. as short as possible. With the perfected 

 apparatus Bose carried out his extended investigations on 

 the optical properties of the electric rays. The scheme 

 adopted was as follows : 



(a) Verification of the Laws of Reflection (plane 



mirror, curved mirror). 



(b) Phenomena of Refraction (prisms, total reflection, 



opacity caused by multiple refraction and reflec- 

 tion ; determination of the indices of refraction). 



(c) Selective Absorption (electrically coloured media). 



(d) Phenomena of Interference (determination of 

 wave-length). 



(e) Double Refraction and Polarisation (polarising 



gratings, polarising crystal, double refraction 

 produced by crystals, by other substances, and 

 by strain ; circular polarisation ; electro-polari- 



