I walked into the next room and saw a long, undulating line of Duplo blocks carefully joined together. "Oh," I said. "What exactly does a vocabulary machine do?"
He gave me a reproachful look, as though I should have known without asking. "It calculates how much you weigh."
Of course. I ought to have guessed that at once.
In other Nicholas-related news, we have finished The Lion, The Witch and The Wardrobe and are three chapters into Prince Caspian. I sometimes wonder whether he's really paying attention, as he wriggles around and stares off into space a lot, but every night he asks to make sure I'm going to read him another chapter...