It's the indication
Of a mirrored reflection
Somewhere along the line
Of what we call the spine.
He felt in modesty
His person was
Half looking-glass,
For why should he
Be doubled?
The glass must stretch
Down his middle,
Or rather down the edge.
But he's in doubt
As to which side's in or out
Of the mirror.
There's little margin for error,
But there's no proof, either.
Again, a serious predicament about not knowing where his center is, and what parts of him are real. It mirrors Bishop’s own confusion in the heat of turmoil.
The Gentleman of Shalott