Copy letter from Herbert Rix, to Dr David Bierens de Haan, Leyden 'Dear Sir, In answer to your query concerning the sheet which I return herewith, No 1672 is not the same as our No. 1545, but no. 1671 (of which you send us only a portion) is the same as 1545. The date, however, should be 13th November, instead of 12th November. Our No. 1545 is, as you conjecture, to Dr Wallis, and is of the same date as No.1544, addressed to Oldenburgh. I am, yours truly, H Rix Asst. Sec. R.S. [Assistant Secretary, Royal Society]'. 2 December 1893