Pictured Puzzles and Word Play / A Companion to the Twentieth Century Standard Puzzle Book - A. Cyril Pearson

The enigma—

I’m but a little letter, still
I have my duties to fulfil;
If off you take
My tail, and make
An alteration in my lot,
Though I seem shorter I am not.

is solved by Note.

This is the full text—

Says Tom to Bill, “Pray tell me, sir,
Why is it that the devil,
In spite of all his naughty ways
Can never be uncivil?”

Says Bill to Tom, “The answer’s plain
To any mind that’s bright;
Because the imp o’ darkness, sir,
Cannot be imp o’ light!”