Analysis of Spirits

Angel spirits of sleep,
White-robed, with silver hair,
In your meadows fair,
Where the willows weep,
And the sad moonbeam
On the gliding stream
Writes her scatter'd dream:

Angel spirits of sleep,
Dancing to the weir
In the hollow roar
Of its waters deep;
Know ye how men say
That ye haunt no more
Isle and grassy shore
With your moonlit play;
That ye dance not here,
White-robed spirits of sleep,
All the summer night
Threading dances light?