Links to most of the numerous "Danny Boy" discussions here are given at:  History of the song Danny Boy

That extra verse is a recent addition, made by somebody who wanted the song to be about Ireland, rather than what, historically, it is: an English song set (at the second attempt!) to an Irish melody, and apparantly with no particular country in mind, though the references to "pipes" and "glens" are typical of the tendency to use romantic Scottish backdrops in popular songs of the time.

Malcolm