The note is undated; in the published letter Gordon N. Ray suggests that it was written in November/December 1859; the note has no salutation but the published letter indicates it is to George Smith.
Francis Mahony, referenced in this letter, was an English satiric poet and journalist who wrote under the pseudonym of Father Prout.
Part of a collection of letters from William Makepeace Thackeray to George D. Smith. Letters in this collection have been described individually in separate catalog records; see collection level record for more information.
Suggesting that Mahony's alterations be omitted; asking "Who is that awful reader?"