The first two lines of the second verse are "O Christ, the Lord of hill and plain, / O'er which our traffic runs amain." The melody to which the second line is sung has an arc, to musically describe that "traffic" travelling over the "hill," and then it levels out around G and F#, depicting the "plain":
To some degree, the breadth of this phrase also compasses the Holy Spirit's being "spread abroad the firmament" in the third verse.
The last two lines of the fourth verse are "Thus evermore shall rise to Thee / Glad praise from air and land and sea," and the melody for the first of these two lines ascends (as if to musically portray the "ris[ing]" of the "Glad praise"):
Furthermore, this phrase ascends chromatically (E to F to F# to G), which seems to make the ascent more obvious when the tune is heard.
