Thanks for the link, 'spaw.
Sian, thank you too for your help. I think Slane is the hymn "Be thou my vision" and "Star of the county Down" is the tune for the hymn with the line "Lay down o weary one, lay down."
Later today I'll try to transcribe the melody for the Dylan song, and then post it.
For one thing, this hymn is major, and both Slane and Star are minor at least in places.
Blessings,
Barbara