"Sometimes I watch you, mark your brooding eyes"

Sometimes I watch you, mark your brooding eyes,
Your grave brow over-weighted with deep thought,
Your mouth's straight line — details of such a sort
That all aloofness in your aspect lies.
And yet when in the dark down from above
You swoop like a great bird or God himself
To kiss, your lips have curves. What changeling elf
Is that soft mouth of passionate close love?