这是福斯特的歌曲《Old Folks at Home》第一段歌词:
way down upon the Swanee River,
far,far,far away.
That's where my heart is turning ever,
that's where the old folks stay.
All up and down the whole creation,
sadly I roam.
Still longing for the old plantation,
and for the old folks at home.
请教，第一行的 down upon 是么意思。谢谢！