Overshot v. Undershot
By which I mean mill wheels.
There is a fascinating article on water-powered mills to be found on “History–Now and Then” giving detailed information on how the ancient grist mills worked. The author, known as “Jerseyman,” explains how overshot wheels were designed and how much more efficient they were than undershot wheels. Immediately I thought of a locally famous overshot wheel at the old Sergeant’s mill near the Wickecheoke. Here’s a picture that says it all–the perfect example of an overshot wheel.