APOLOGETIC

His thunderbolt yielding nothing to that which justice
    Draws from your hand,
When she wishes to punish a crime or misdeed,
    Through the work of Vulcan. Vulcan was the Roman god of fire and the forge; here, the poet compares the man-made "thunder" of a cannon to the divine lightning Vulcan forged for Jupiter.

He will find a way to reduce to ruin
    The most elevated fortresses,
And men, too, by his crude machine,
    Will see themselves swept away.

But to better assist him, I shall see that Megaera,
    Tisiphone, and Alecto, These are the three Furies (or Eumenides) of classical mythology—deities of vengeance who personified anger and retribution.
Will make him invent this torture of war,
    And this deadly ball. The original French peloton refers here to a projectile or cannonball.

And they will suggest to him how he must put
    His knowledge to work:
And how one extracts Sulfur and Saltpeter,
    From a rotting soil. Saltpeter (potassium nitrate), a key ingredient in gunpowder, was historically harvested from "rotting" organic matter and mineral crusts found in cellars and stables.

Aconite, monkshood, venom, nor the plague,
    Arsenic, nor poison,
Will be its equal; they will seem like a mere feast,
    Compared to his Cannon.

Thus his murderous strikes will take vengeance
    For so many enormities,
And will sack this troublesome race
    Through his clever inventions.

So that without troubling you, the unbridled malice
    Of these ambitious men,