Copy letter from Robert William Frederick Harrison to The Secretary, The Imperial Merchant Service Guild, The Arcade, Lord Street, Liverpool 'Dear Sir, Referring to your letter of March 8, the paper by Sir William Abney on Colour-Blindness has just been published in the Proceedings of the Royal Society, Series A, No. 565. The number may be obtained from Messrs Harrison & Sons, 45 St Martin's Lane, London, WC, price 2/6.' 15 April 1910