Copy letter from Herbert Rix, to W G Spencer, 25 Brook Street, Grosvenor Square, W. 'Dear Sir, Many thanks for your note. I shall put the tracings in hand, but please observe that they are being done by zinco process and that corrections are always difficult, sometimes impossible, so I hope they will not amount to much. I am, yours truly, H Rix Asst. Sec. R.S. Assistant Secretary, Royal Society]'. 28 April 1894