I'm persuading myself that the 1868 reference to "Valparaiso, Round the Horn" isn't to this song but to the one commonly called "Rounding the Horn" or "The Girls Around Cape Horn" - about the ship "California," the frigate "Amphitrite," the ship "Conway," etc. (Roud 4706).

The style and diction of "Paddy Lay Back" is just too post-romantic for me. There are no "poetic" cliches, no sentimentality, no "brave boys," etc.: circumstantial, plain-spoken, first-person realism only.

It's the fresh first-person realism, undiluted, that impresses me: the narrator is an individual, not a conventional figure or a "we." He insists that he did and saw these many, very specific things personally and makes no attempt to generalize, moralize, or aestheticize them. The style just doesn't strike me as typical of the 1860s or earlier.

Unless new evidence shows up, I'd date "Paddy" to ca1885 or later.

Tentatively.