While some versions of The Marriage of Heaven and Hell end after the last Memorable Fancy, others include two more sections at the end.
The first of these—the ninth section overall—is "A Song of Liberty."
Remember when we told you about Blake's interest in politics, back in "In a Nutshell"? Well, go read that if you don't.
In this case, the section is a list of 20 sentences or short paragraphs about the various revolutions going on around the world at the time Blake was writing this.
The speaker describes how "The Eternal Female groan'd" (9.1), which seems to symbolize the other countries that are clamoring to be free.
The speaker says that things are too quiet in "Albion," or England (9.2).
Next he calls for France and Spain to break free of their rules (the monarchy and the Catholic Church, respectively).
The speaker describes a "new-born fire," which is located "by the Atlantic sea" (9.8). This is more symbolism to reference a newly-independent (when Blake was writing, anyway) America.
The speaker then calls on London's citizens to open their eyes ("enlarge they countenance") (9.12). Then—and there's no other way to put this—he calls for the Jew to stop counting gold. He also calls for "winged thought" to "widen [the] forehead" of the African.
So… yeah—the speaker's definitely got some backwards, racist views going on here.
The gist of what he's calling for, though, is that the rest of world wake up to the energy of the recent revolutions in America and France.
What follows is a pretty entailed fantasy in which "the jealous king" and his buddies are forced to run away and then are buried in the ruins that they have created (9.12-9.17).
The king tries to push through a wasteland with his ten commandments, but his world has changed.
The speaker ends with the image of the dawn: "Morning plumes her golden breast" (9.19). The revolution is complete, according to the speaker: "Empire is no more! And the now the lion and the wolf shall cease" (9.20). Good times all around, gang.