Get out the microscope, because we’re going through this poem line-by-line.
"I was right joyful of that wall of stone,
That shut the flowers and trees up with the sky,
And trebled all the beauty: to the bone,
"Yea right through to my heart, grown very shy
With weary thoughts, it pierced, and made me glad;
Exceedingly glad, and I knew verily,
"A little thing just then had made me mad;
- The speaker says that she actually enjoyed the stone wall – she didn't feel trapped by it; instead, its presence made everything inside it seem even more beautiful.
- All that beauty went straight to her heart and made her happy.
- She needed cheering up, because, remember, she'd been feeling sad and "careless" for a few months at this point.
- She says she also realized that something was making her slightly "mad" (insane) at that moment – or that some little thing could potentially make her "mad."
- The tense of the verb makes it unclear – did something already make her insane, or did she just realize that she was teetering on the brink, so that some little thing could make her go crazy?
- She doesn't say what that something was, though, or why it would make her "mad."