There are two lectures, Reading and Writing, which he delivered as part of Yale University's Tanner lecture series. Filled with marvellous quotes and thoughts. Page 224.
Everybody used to verbalize as they read. Indeed during the Middle Ages people read aloud, and everybody knows the story about the scholar who had to discontinue his studies because he had a sore throat. Because they verbalized — I hate that word, but I can’t find another — they truly took in — drank in, one might almost say — what they read and it was impressed on their minds forever.