Read the poem and answer the question.
The pale moon moved like a silver boat,
A lantern hanging far and high;
The sleepy houses closed their eyes,
When silver silence filled the sky.
The little brook sang a silver song,
The tall trees bowed to watch her go;
Soft shadows slid on street and stone,
And night was a velvet show.
"When silver silence filled the sky" is alliteration because of the repeated: