84 LIFE AND WORK OF SIR JAGADIS C. BOSE 



Enough now of this theory of photography : we may 

 pass to Bose's ' Artificial Retina.' His various forms of 

 electric receiver were sensitive to the waves longer than 

 those of heat ; whereas the photographic plate is normally 

 sensitive only to the short waves towards the opposite 

 ends of the immensely long and varied spectrum. But, he 

 asked, may it not be possible to find substances of wider 

 and wider range of receptiveness ? The ideal substance 

 would be one sensitive through this enormous range, and 

 responding not only to our visible light, but to all the many 

 octaves of the invisible light, which stretch out on each 

 side of the single octave of our colour-sensation. Hence 

 a new and systematic series of tests of the range of 

 responsiveness of natural and artificial substances without 

 number, which is indicated, as begun, in the paper on 

 'Electric Touch,' but has never yet been completed and 

 published. Still, the desired substance was at length 

 found one so exquisitely sensitive to the long electric waves 

 as to supersede previous materials in the electric receiver 

 of wireless telegraphy, already mentioned ; yet giving also 

 the same unquestionable galvanometric answer to thermal, 

 luminous and ultra-violet rays. 



To reduce this all-perceiving super-retina to the level 

 of our human perception was next easy ; for on placing 

 in front of it a flask of water, to represent the aqueous 

 humour, the electric and thermal rays are now absorbed, 

 and thus can no longer be responded to ; and similarly as 

 to some of the ultra-violet rays as well. Thus this ' retina ' 

 could now practically only ' see ' the rays which are visible 

 to ourselves and signal their impulse to its galvanometric 

 ' brain ' behind, while on removing the absorbent water its 

 innumerable octaves of wider perception were restored. As 

 Bose remarked, ' Perhaps we do not sufficiently appreciate, 

 especially in these days of space-signalling by Hertzian 

 waves, the importance of that protective contrivance 

 which veils our sense against insufferable radiance/ Here, 

 then, is a first -class example of ' the wonders of science ' ; 



