Alliteration is also an important factor in the rhythm of this poem. A poem has many rhythms. There is the rhythm set up by the stresses, which in English appear at regular intervals. There is the rhythm set up by the line units, especially when, as here, the line endings are marked by rhythm. There is the rhythm set up by the pauses between grammatical units, or marked in different ways by punctuation and layout. And there is also the rhythm set up by various interior sound repetitions, including alliteration.