Victorian illustration to download showing a floating tidal mill on a river. Below decks is a wheel, or screw propeller, which is turned by the river current. The wheel drives a pulley, which works a saw, tended by a carpenter. Another man adjusts the wheel mechanism. This was an experimental vessel belonging to the Tidal Mill Company which was moored in the Thames at Southwark in 1847. The company’s experiments showed that a 7ft wheel could provide 4 horse power with a current or tide running at 4mph; the bigger the wheel, the more horse power.