Seamus Heaney's "Digging" describes a man's journey through time to observe, stand in awe of, and struggle to measure up to, the greatness of two men in the speaker's past.
First the narrator talks of his father. He is writing from his memory, offering the sensory details—the sights, the smells and the sounds—alive in his memory. The narrator holds his pen—it rests snugly, like a gun. This is an interesting simile, but perhaps it alludes to the quotation, "the pen is mightier than the sword," giving the sense that it may be a small object, but the pen has its own power.
The speaker hears the sound of his father outside:
Under my window a clean rasping sound
When the spade sinks into gravelly ground:
My father, digging. I look down...
Here the speaker is looking (in the present) at his father digging (in the present). He describes the sound of the spade working its way into the ground, "rasping" against pebbles in the dirt.
The narrator now notes that he is engaging a memory of his father in the garden—where he...
...comes up twenty years away
Stooping in rhythm through potato drills
Where he was digging.
His father has years of experience: there is a rhythm in his digging as he unearths the potatoes. He holds the spade comfortably—it fits snugly against his knee just as the speaker's pen rests against his finger...from the practice of long days, years, of digging potatoes that the children would gather behind him...
Loving their cool hardness in our hands.
The speaker sets two lines apart—not only to praise his father, but to bridge that memory with a man the speaker also remembers: his grandfather.
By God, the old man could handle a spade,
Just like his old man.
This man was a master in his own right, using his shovel for a different purpose, but with precision and skill unequalled by any man living nearby.
My grandfather could cut more turf in a day
Than any other man on Toner's bog.
The narrator recalls taking his grandfather a bottle of milk as he worked. He drank and quickly returned to the task at hand. Even as a youngster, the speaker could gauge his grandfather's skill:
...Nicking and slicing neatly, heaving sods
Over his shoulder, digging down and down
For the good turf. Digging.
The speaker is able to recall the slapping sound of the "soggy" peat, the smell of the potato mold, and the sight of precise edges of the turf: things that sharply bring the past to the forefront of his mind. He infers there is a great difference between him and his kinsmen:
The cold smell of potato mold, the squelch and slap
Of soggy peat, the curt cuts of an edge
Through living roots awaken in my head.
He admits that he has no spade—no skill as they had—to dig for the cool hard potatoes or the "good turf."
But I've no spade to follow men like them.
Then the reader is reminded of the narrator's pen. And while he is unfamiliar with how to use a spade as these great men before him, he notes that he can "dig" for the "good turf"—the important words—with his pen.
...The squat pen rests.
I'll dig with it.
The strength of the writer's feelings for his kinfolk is obvious. However, it is the imagery that so speaks to the reader with words like "soggy," "squelch," "slap," "cool hardness," and the "cold smell." It is imagery like this that demonstrates the narrator's skill with his pen, which can be evenly compared to the skill of the men who came before him: their tools are different, but equally effective.