She stopped at a place where they could peer into a portal of the Stock Exchange. 'Just as a whole workshop can be powered by a mill-wheel, driven by a trickle of water in a race, or by a breath of air on the blades of a windmill, so the movement of goods through yonder Weigh-House is driven by a trickle of paper passing from hand to hand in there ' (pointing to the Stock Exchange) 'and the warm wind that you feel on your face when you step into the Maiden.'