Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to the Hon. Secretary [RB Asquith Ellis Esq. Associate Member of the Institution of Mechanical Engineers], James Watt Centenary Advises a letter intended for Sir Richard Threlfall was by mistake put into an envelope addressed to the recipient, and would appreciate its return at his earliest convenience. He encloses the letter intended for the recipient which was accidentally sent to Sir Richard Threlfall. 16 August 1919