The first line of the hymn is "Thy strong word did cleave the darkness." "Darkness" is sung with a melisma (Ab G F at the end of the second measure), musically giving a sense of having been "cleave[d]."
The fourth verse begins with the lines "From the cross Thy wisdom shining / Breaketh forth in conqu'ring might." Similar to the cloven "darkness," here "Breaketh" is sung with a melisma (C Bb C Db) musically giving something of a sense of the word's meaning.
The second verse starts with the lines "Lo, on those who dwelt in darkness, / Dark as night and deep as death" (adapted from Isaiah 9:2). Reflecting that "deep as death" musically, there's a descent in the melody (Bb Ab G F).
