| Quote #1 A sunbeam which hath lost its way, |
The small amount of sunlight that makes its way into the dungeon seems like it doesn't belong there – the speaker thinks it must have gotten "lost." Natural beauty has no place in a dungeon like his!
| Quote #2 And truly might it be distress'd |
The speaker might be banished from the natural world, but he still uses natural metaphors and similes to describe the people he loves.
| Quote #3 A polar day, which will not see |
The speaker's youngest brother's goodness and beauty remind him of a "polar day" during the summer – a day with no sunset.