Most lovers of this film will have difficulty finding the words of the hymn sung to the tune Penparc, because they used here the words of a different hymn, usually sung to the tune 'Aylesbury'. So what we hear in the movie (before the deacons' meeting in chapel, and in both scenes when there are deaths in the mineshaft) is actually the first verse of "Ai marw raid i mi", written by John Hughes, 1776-1843. Here are the Welsh words with an English translation:

Ai marw raid i mi,
A rhoi fy nghorff i lawr?
A raid i'm henaid ofnus ffoi
I dragwyddoldeb mawr?

Must I die
And lay my body down?
And must my fearful soul flee
To a great eternity?