"Her Brow was fair."

Can any of your many readers inform me of the author of the following lines, which I copy as I found them quoted in Dr. Armstrong's *Lectures*: "Her brow was fair, but very pale, And looked like stainless marble; a touch methought would soil Its whiteness. On her temple, one blue vein Ran like a tendril; one through her shadowy hand Branched like the fibre of a leaf away."