Read this poem about the American colonists fighting the first battle of the Revolutionary War. First, identify the figurative language used in the line shown in boldface and determine its meaning. Then, explain how this figurative language contributes to the overall meaning of the poem.

Passage
By the rude bridge that arched the flood,
Their flag to April's breeze unfurled,
Here once the embattled farmers stood,
And fired the shot heard round the world.

The foe long since in silence slept;
Alike the conqueror silent sleeps;
And Time the ruined bridge has swept
Down the dark stream which seaward creeps.

On this green bank, by this soft stream,
We set to-day a votive stone;
That memory may their deed redeem,
When, like our sires, our sons are gone.

Spirit, that made those heroes dare
To die, and leave their children free,
Bid Time and Nature gently spare
The shaft we raise to them and thee.

—Ralph Waldo Emerson, "Concord Hymn"