Copy letter from Robert William Frederick Harrison to the Director, Cambridge Scientific Instrument Co., Ltd, Cambridge 'As requested in your letter of the 29th instant, I have instructed our printers to prepare and forward direct to you electros of plates 6, 7, 8, and 9 illustrating Mr C T R Wilson's paper in the Proceedings of the Royal Society, volume 87, A. This is done, of course, subject to the formal consent of Council, which, however, may be anticipated.' 31 January 1913