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Shannon News, 29 June 1923, Page 2

A curious instance of colour-blind-ness is reported in one of the American scientific journals. A college student who was being tested had no difficulty in distinguishing red from green. But he found anything written in blue ink hard to read indeed, a blue-black writing fluid used on white paper was hardly visible to him until it had turned quiite black. A blue pencil made a! mark that seemed to him scarcely different from that made by white chalk. When al blue, ribbon was used with a typewriter the effect was just. as though the keys, had hit the paper direct without a) ribbon, and the writing could only be read when the paper was held on a slant, The subject of this experiment sab that the first colour difficulty, he could, remember was in his childhood, \vhen he was puzzled to know -what people :ne;ant in/.talking of the sky as blue.