The song in the DT seems to be a rewrite of this song:

Lyrics from Bodleian Library Broadside Ballads, Harding B 11(4304); other copies--Harding B 11(1698), Harding B 15(88b), Harding B 20(43)—are nearly identical.

DOWN IN A COAL MINE

1. In me you see a collier, a simple honest man
Who strives to do his very best to help his fellow-man.
We toil away from morn till night where hard work's to be found,
Digging dusty diamonds from underneath the ground.

CHORUS:
Down in a coal mine, underneath the ground,
Where a gleam of sunshine never can be found,
Digging dusty diamonds all the season round,
Down in a coal mine, underneath the ground.

2. In the morning when we go to toil, and down the mine we go,
Contented with our lot in life, and free from care or woe,
We often think of home and wife, and hearts that's filled with mirth,
While digging up the fuel from the bowels of the earth.

3. You often read of accidents, which happen down the mine,
How hundreds of poor colliers are shortened of their time:
Explosions they are numerous, and caused by fire-damps,
Which when the gas escapes, it comes in contact with our lamps.

4. But when the wintertime comes in, the collier's worth is found:
Old England's commerce it is spread to all the nations round.
Let those at home rejoice and sing with hearts and voices full,
For what would England do without the boys that dig the coal?