Seamus Heaney: "What will be our trace"

From "Station Island," II. The narrator converses with the shade of William Carleton:

'The angry role was never my vocation,'
I said. 'I come from County Derry,
where the last marching bands of Ribbonmen

on Patrick's Day still played their "Hymn to Mary".
Obedient strains like theirs tuned me first
and not that harp of unforgiving iron

the Fenians strung. A lot of what you wrote
I heard and did: this Lough Derg station, flax-pullings, dances, fair-days, crossroads chat

and the shaky local voice of education.
All that. And always, Orange drums.
And neighbours on the roads at night with guns.'

'I know, I know, I know, I know,' he said,
'but you have to try to make sense of what comes.
Remember everything and keep your head.'

'The alders in the hedge,' I said, 'mushrooms,
dark-clumped grass where cows or horses dunged,
the cluck when pith-lined chestnut shells split open

in your hand, the melt of shells corrupting,
old jam pots in a drain clogged up with mud—'
But now Carleton was interrupting:

'All this is like a trout kept in a spring
or maggots sown in wounds—
another life that cleans our element.

We are earthworms of the earth, and all that
has gone through us is what will be our trace.'
He turned on his heel when he was saying this

and headed up the road at the same hard pace.