Now my friends emerge Beneath the wide wide Heaven—and view again The many-steepled tract magnificent(21-23)
The word "Heaven" does not have a specifically religious meaning here – it just means "sky." But the phrase "many-steepled track magnificent" compares the hills that poke out of the landscape to the steeples of country churches that are visible when you approach a village. Rather than being confined to one church, as most villages were, the landscape has many of these metaphorical places of worship. In other words, nature beats man.
gaze till all doth seem Less gross than bodily; and of such hues As veil the Almighty Spirit, when he makes Spirits perceive his presence. (41-44)
These lines are the most difficult in the poem. The speaker says that the landscape is not just blind matter, not "gross" like a lifeless rock or stump. Instead, nature is like a body that houses that "soul" of the Almighty Spirit of God. A philosopher might find this imagery to be evidence of "Transcendentalism" or "Idealism." The basic idea is that the "real world" – the true nature of things – lies "behind" or "inside" the visible world.
Henceforth I shall know That nature ne'er deserts the wise and pure; No plot so narrow, be but Nature there No waste so vacant, but may well employ Each faculty of sense, and keep the heart Awake to Love and Beauty! (61-66)
Try taking out the word "nature" in these lines and replacing it with the word "God." Do you see a substantial difference?
Had cross'd the mighty Orb's dilated glory While thou stood'st gazing; or, when all was still, Flew creaking o'er thy head, and had a charm For thee, my gentle-hearted Charles, to whom No sound is dissonant which tells of Life. (74-78)
The bird is a traditional symbol for the spiritual soul that flies "above" the material world. But this bird makes an awkward "creaking" sound that can only be understood in the context of nature as a whole.