And BTW, here is the offending lyric, as I remember it, from my school days. I've done it in minstrel dialect, which is the way I remember us singing it too.

I jumped aboard de telegraph

and trabelled down de ribber,

the electrie fluid magnified

and killed ten thousand nigger,

De bulgine burst, de horse ran off

I really thought I'd die

I shut my eyes to hold my breath

Susannah don't you cry.