 The poem contains a complicated use of assonance ( the repetition of vowel sounds ) , as evident in line 19 , " O why did ye not melt , and leave my sense " , where the pairs ye / leave and melt / sense share vowel sounds . A more disorganized use of assonance appears in line 31 , " A third time pass 'd they by , and , passing , turn 'd " , in which the pairs third / turn 'd , time / by , and pass 'd / passing share vowel sounds . The first line exemplifies the poem 's consistent iambic <unk> <unk> : 
