How the Chimney-sweeper's cry Every blackning Church appalls; (9-10)
The chimney sweeper makes us think of confinement in several ways. First, we have the image of some little kid climbing down a chimney—that's a pretty confined space if we ever saw one. Second, lots of these chimney sweepers back in the day didn't have a whole lot of choice about whether or not they wanted to work.
And the hapless Soldier's sigh Runs in blood down Palace walls. (11-12)
All soldiers are "confined" to certain rules and regulations—they've gotta do what they're told, more so than other people. The repetition of the S sound all over the place ("hapless," "Soldier's," "sight," "walls," "runs") reflects the restrictions of a soldier's life.