Copy letter from Herbert Rix, to Messrs Clay & Sons, Cambridge 'Dear Sirs, We are sending you today 4,000 slips. We have had a little box made to contain 1,000, and we can, if you like, send this to you filled at short intervals. Yours faithfully, H Rix Asst. Sec. R.S. [Assistant Secretary, Royal Society]'. 13 June 1889