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which we could not hear, and of responding to fluoric rays which 

 would affect no fibre of our retinal structure. In reference to 

 human vision, it was suggested that the rods of the retina might 

 be responsive to the vibrations of the primary colours, and that 

 combinations would give rise to an appreciation of every tint in 

 the spectrum — a natural three colour process — the weakness or 

 failure of any one set resulting in varieties of colour-blindne.— . 

 Colour-blindness, the lecturer remarked, was almost always a 

 congenital defect, only one case of its accidental acquirement 

 having come to his knowledge — an instance communicated by 

 Professor Tyndall. A sailor who occupied his spare time in wool- 

 working was one evening engaged on a rose, and, endeavouring 

 in the dusk to match the wools required, felt what he described 

 " as if something had snapped in his head." He put aside his work 

 for the night, but next day found, that he was quite unable to 

 recognise colour at all. Twelve years later, being experimented 

 upon, he found that he could just perceive the colour sensation 

 red when looking through a red screen at the intense light of the 

 electric arc. After dealing briefly with pseudoscopic and stereo- 

 scopic vision, the lecturer said that binocularism was a very 

 well-known optical effect; but the corresponding effect with 

 sound-waves usually passed unnoticed unless under exceptional 

 conditions. A very striking instance of this was given. At one 

 of the Paris Exhibitions was an arrangement to illustrate 

 " stereoscopic " hearing. A telephone transmitter was fitted on 

 the right and on the left of the stage of the Opera House, and 

 these transmitters communicated, each by a separate wire, with 

 receivers at the Exhibition. On placing the receivers from the 

 right and left of the stage to the right and left ears respectively, 

 a most wonderful effect was obtained — quite a new sensation. 

 The listener could locate the relative position of every instrument 

 in the orchestra, and could easily follow the movements of the 

 singers on the stage, etc. As the structure of the compound eyes 

 of insects, and their probable function, was the subject of dis- 

 cussion at the previous meeting of the Club, it was not referred 

 to at any length on this occasion, except to show that as insects 

 lived in the same air and light as ourselves, similar — or at least 

 analogous — structures in their organs might be looked for ; hence 

 we found the cornea, the lens, something corresponding to the 

 iris, the retina, the optic nerve, and the sensory ganglia, all 



