Copy letter from Herbert Rix, to Professor Archibald Barr, Royston, Dowanhill, Glasgow 'Dear Prof. Barr, Our engraver says that it would be convenient for him to have the negatives of your illustrations, but that it is not necessary if inconvenient to send them & that in whatever shape they come we can adapt them to our needs. Yours truly Herbert Rix Asst. Sec. RS [Assistant Secretary, Royal Society]'. 14 May 1891