Copy letter from Herbert Rix, to Dr Theodore Cash, 25 Dee Street, Aberdeen 'Dear Dr Cash, In answer to yours of the 13th the original MS [manuscript], however defaced, must be returned here and deposited in our Archives if you wish to keep your date. The alterations, however, appear to be somewhat extensive, and perhaps the simpler way will be to re-date the paper, in which case, the old MS need not come here. It is entirely for you to decided which course to pursue. Yours truly Herbert Rix Asst Sec R.S [Assistant Secretary, Royal Society]'. 15 October 1891