There's no reason to believe, from the online _Agincourt_ "diary," that the "1848 text" or even the title of "A Hundred Years Ago" was recorded by anyone who was present on the voyage or even alive in 1848.

The online writer seems to have taken the shanty from Lubbock's book to flesh out the story of the voyage, assuming that Lubbock's "Old Chanty" "must have been" sung by the _Agincourt_ crew.

Lubbock doesn't print the original "midshipman's log" he refers to. He quotes a few lines, but mostly paraphrases and expands the information in the logbook.