John Smeaton, FRS
1796
The 18th century engineer John Smeaton (1724-1792) is most famous for his work on the Eddystone Lighthouse, but he is also recognized for making some of the most important changes in waterwheel technology since the year 1000. Although he was not an inventor, he was an innovator. He pioneered the use of cast iron in millwheels, introducing cast-iron shafts and gears. His modifications improved the durability and efficiency of waterwheels and allowed for the development of the steam engine.

Illustration from:
Experimental Enquiry Concerning the Natural Powers of Wind and Water to Turn Mills and Other Machines Depending on Circular Motion, by John Smeaton in 1796. It was published in London and printed for S. and J. Taylor.