Copy letter from Herbert Rix, to Professor Joseph Norman Lockyer, Fellow of the Royal Society 'Dear Sir, We are sending you this afternoon original and proof of one of your spectra done by the Direct Photo-Engraving Co. you will let us know whether this is satisfactory, the rest shall be put in hand at once. Yours faithfully, H Rix Asst. Sec. R.S. [Assistant Secretary, Royal Society]'. 16 July 1894