Now, my friends emerge Beneath the wide wide Heaven -- and view again The many-steepled tract magnificent Of hilly fields and meadows, and the sea, With some fair bark, perhaps, whose sails light up The slip of smooth clear blue betwixt two Isles Of purple shadow!
Line 20 breaks off into a new stanza as the speaker's friends break out of the ravine and into the wide open air.
They can see the sky above like "Heaven," and the hills and meadows stretching out into the distance. The tops of the hills look like so many "steeples" of churches.
You could easily miss the controversial point made in these lines: nature is like a church. Coleridge and Wordsworth were sometimes accused of being "Pantheists" who believed that God and Nature were the same thing, and you could find support for that view in these lines.
They also see the ocean, and maybe even a ship ("fair bark") that sails between two islands that appear "purple" at this time of day.
Yes! they wander on In gladness all; but thou, methinks, most glad, My gentle-hearted Charles! for thou hast pined And hunger'd after Nature, many a year, In the great City pent, winning thy way With sad yet patient soul, through evil and pain And strange calamity!
The speaker's imagined vision of the nature walk reaches a climax with the image of the ocean and the little sailboat, and he starts to get overheated, shouting, "Yes!"
All of the speaker's friends are happy, but he thinks his friend Charles (as in, Charles Lamb) must be the happiest of all. He calls Charles, "gentle-hearted," which really makes him sound, well, like a lamb.
Charles loves nature. In fact, he has a hunger for it that has been built up from all the time he has spent in the city.
Turns out the speaker isn't the only one who has been sentenced to a metaphorical "prison" sentence. Lamb has been "pent" up in London, where he works. He has a "sad" and melancholy soul because he has lived through a lot of bad things, including evil, pain, and "strange calamity."
Actually, Lamb did suffer a terrible catastrophe in his life when his sister suffered a fit of mental illness and stabbed their mother to death. This is a truly horrifying story and helps to explain Coleridge's almost fatherly attitude toward Lamb in this poem. After all he has been through, the speaker's opinion is that Charles deserves the beauty of this day.