Copy letter from Robert William Frederick, to the Direct Photo-Engraving Company, 9 Barnsbury Park, N. 'Dear Sirs, Referring to the illustrations of Messrs Worthington & Cole's paper, I beg to inclose a letter from the Authors and to ask that you will, in accordance with the request made in the third paragraph, make prints from those negatives sent to you on April 17 but of which you have not sent us proofs. Kindly return Prof. Worthington's letter to me. I am, yours faithfully, Robt Harrison Asst. Sec. RS. [Assistant Secretary, Royal Society]'. 19 May 1896