Hull of SS Francis Smith with Smiths patent screw propeller, 1836.

UNITED KINGDOM - JULY 30: This basic model represents a screw driven steam launch constructed at Wapping, London, in accordance with Francis Pettit Smith's (1808-1874) patent of 1835. On trials, when one turn of her two turn wooden propeller was accidentally broken away, the launch was observed to increase her speed. Smith, originally a farmer by occupation, never profited financially from his lifetime devotion to the cause of screw propulsion, but was knighted in 1871. (Photo by SSPL/Getty Images)