Hydraulic turbines are water motors that turn at great speed. The metal turbines at this site used the pressure of water created by the dam to generate power. They were more efficient and more durable than wooden water wheels, and they probably replaced breast wheels in the Valley Falls mill complex before 1870. At first, they were used only for mechanical power, driving machinery with shafts, gears, belts, and pulleys. From 1922 to 1925, a generator linked to one of the turbines provided electrical power. The cast iron circular base and floor plate visible in the Southeast Addition were part of the 54-inch turbine installation. Water enters through the fixed guides of this turbine and presses against the buckets of its moving runner before discharging at the bottom. A cylindrical gate moved up and down, regulating the flow of water to match the demand for power. The largest turbine on this site was a Holyoke type with a runner 54 inches in diameter. Installed in 1901, it replaced an earlier turbine in the Southeast Addition.