There are miners still
In the underground rivers
Of West Moor and Palmersville.
There are guttering cap-lamps bound up in the roots
Where the coal is beginning again.
They are sinking slowly further
In between the shiftless seams,
To black pools in the bed of the world.
In their long home the miners are labouring still -
Gargling dust, going down in good order,
Their black-braided banners aloft,
Into flooding and firedamp, there to inherit
This line pulls together and explains the essence of the poem; the miners are ‘labouring still’ in spirit. 
 Their ‘long home’ is literal and figurative. These ghostly miners inhabit a seam of coat, but ‘long’ also refers to time.
Fantasia on a Theme of James Wright