Annette, can't help with your grandfather's song -- but there is a more recent song from Ian Sinclair (of the Scottish group Mirk, from Thurso) on the same lines; I think it may have been commissioned for a Radio Scotland programme 20-odd years ago, but I've lost any link to the source.

I can vaguely hear the melody in my mind and the lines that end with ….. in Patagonia.

(Hope someone else can help with more info.)