Copy letter from Herbert Rix, to Professor Michael Foster, [Royal Society] 'Dear Sir, I am afraid we cannot offer anything that can be called "proof" as to the posting of Prof. Sylvester's card, but I may say that a double check is used --- the cards and envelopes are written separately by two different persons, and it is scarcely likely that both would omit a name; and in addition to this the addressed envelopes are called over and checked with the list independently ^just before posting^. Personally, I am pretty confident that no mistake could occur. I am, yours truly, H Rix Asst. Sec. R.S. [Assistant Secretary, Royal Society]'. 4 May 1894