Analysis of Hugo's "pool in the forest"

How calm, how beauteous and how cool--
 How like a sister to the skies,
Appears the broad, transparent pool
 That in this quiet forest lies.
The sunshine ripples on its face,
 And from the world around, above,
It hath caught down the nameless grace
 Of such reflections as we love.

But deep below its surface crawl
 The reptile horrors of the night--
The dragons, lizards, serpents--all
 The hideous brood that hate the light;
Through poison fern and slimy weed
 And under ragged, jagged stones
They scuttle, or, in ghoulish greed,
 They lap a dead man's bleaching bones.

And as, O pool, thou dost cajole
 With seemings that beguile us well,
So doeth many a human soul
 That teemeth with the lusts of hell.