Lewis Carroll and Alfred, Lord Tennyson, became improbable acquaintances in the 1850s, a few years before Carroll published Alice’s Adventures in Wonderland. The young author sent a letter to his cousin, May 11, 1859, after one memorable visit to the laureate: Tennyson told us that often on going to bed after being engaged on composition he had dreamed long passages of poetry (‘You, I suppose,’ turning to me, ‘dream photographs?’) which he liked very much at the time, but forgot entirely when he woke. One was an enormously long one on fairies, where the lines from being very long at...