"The ease with which our prose admits 'blank verse lines', and the difficulty which many find in detecting them, are further proofs of the same fact. Hence all poetry in this metre has to be read with what we may call 'double audition'."

Thank you for tracking down the references!

I don't think I agree with Lewis that rhapsodizing is strictly to be avoided, but he's right about needing to learn to listen for it. (I said, pentametrically.)