[Composed, probably, in Switzerland, in the summer of 1816. Published in Hunt's "Examiner", January 19, 1817, and with "Rosalind and Helen", 1819.]
1.
The awful shadow of some unseen Power
Floats though unseen among us,—visiting
This various world with as inconstant wing
As summer winds that creep from flower to flower,—
Like moonbeams that behind some piny mountain shower,
It visits with inconstant glance
Each human heart and countenance;
Like hues and harmonies of evening,—
Like clouds in starlight widely spread,—
Like memory of music fled,—
Like aught that for its grace may be
Dear, and yet dearer for its mystery.
2.
Spirit of BEAUTY, that dost consecrate
Shelley begins the next four lines by repeating the word ‘like’, creating a rhythmic pattern that holds the reader’s attention — a device known as  anaphora . The repetition gives emphasis to the importance of the ‘Power’ and yet demonstrates the impossibility of pinning down the description. None of the examples is adequate for Shelley.
Hymn To Intellectual Beauty