Before revision: + Principle of operation of a pound lockFor a boat going upstream: 180pxFor a boat going downstream:1–2.The boat enters the lock.8–9.The boat enters the lock.3.The lower gates are closed.10.The upper gates are closed.4–5.The lock is filled with water from upstream.11–12.The lock is emptied by draining its water downstream.6.The upper gates are opened.13.The lower gates are opened.7.The boat exits the lock.14.The boat exits the lock.
After revision: + Principle of operation of a pound lockFor a boat going upstream: 224pxFor a boat going downstream:1–2.The boat enters the lock.8–9.The boat enters the lock.3.The lower gates are closed.10.The upper gates are closed.4–5.The lock is filled with water from upstream.11–12.The lock is emptied by draining its water downstream.6.The upper gates are opened.13.The lower gates are opened.7.The boat exits the lock.14.The boat exits the lock.