whoever wrote the line "the sheep on the hillside lay white as the snow" had obviously never seen sheep and snow in the same context.

Anyway, apparently it was Nahum Tate. Mr Tate, with all due respect Sir, you were obviously blind. I guess it doesn't snow that often in Ireland. The song is a bit crap too. But amusing to see that the English needed an Irish guy to write their poems. 
I think I've insulted everyone available now, my work here is done.