Water mill in the context of "Flour"

A fall line (or fall zone) is the area where an upland region and a coastal plain meet and is especially noticeable at the place rivers cross it, with resulting rapids or waterfalls. The uplands are relatively hard crystalline basement rock, and the coastal plain is softer sedimentary rock. A fall line often will recede upstream as a river cuts out the uphill dense material, forming "c"-shaped waterfalls and exposing bedrock shoals. Due to these features, riverboats typically cannot travel any further inland without portaging, unless locks are built. The rapid change of elevation of the water and resulting energy release make the fall line a good location for water mills, grist mills, and sawmills. Seeking a head of navigation with a ready supply of water power, people have long made settlements where rivers cross a fall line.

Comminution is the reduction of solid materials from one average particle size to a smaller average particle size, by crushing, grinding, cutting, vibrating, or other processes. Comminution is related to pulverization and grinding. All use mechanical devices, and many types of mills have been invented. Concomitant with size reduction, comminution increases the surface area of the solid.

For example, a pulverizer mill is used to pulverize coal for combustion in the steam-generating furnaces of coal power plants. A cement mill produces finely ground ingredients for portland cement. A hammer mill is used on farms for grinding grain and chaff for animal feed. A demolition pulverizer is an attachment for an excavator to break up large pieces of concrete. Comminution is important in mineral processing, where rocks are broken into small particles to help liberate the ore from gangue. Comminution or grinding is also important in ceramics, electronics, and battery research. Mechanical pulping is a traditional way for paper making from wood. The mastication of food involves comminution. From the perspective of chemical engineering, comminution is a unit operation.

A sluice (/slus/ SLOOS) is a water channel containing a sluice gate, a type of lock to manage the water flow and water level. There are various types of sluice gates, including flap sluice gates and fan gates.

Sluices are used for channeling water toward a water mill, including for transporting logs from steep hillsides. Different terms are used regionally for sluices; the terms sluice, sluice gate, knife gate, and slide gate are used interchangeably in the water and wastewater control industry.

The Watt steam engine was an invention of James Watt that was the driving force of the Industrial Revolution. According to the Encyclopædia Britannica, it was "the first truly efficient steam engine", with the history of hydraulic engineering extending through ancient water mills, to modern nuclear reactors.

Sutter's Mill was a water-powered sawmill on the bank of the South Fork American River in the foothills of the Sierra Nevada in California. It was named after its owner John Sutter. A worker constructing the mill, James W. Marshall, found gold there in 1848. This discovery set off the California gold rush (1848–1855), a major event in the history of the United States.

The mill was later reconstructed in the original design and today forms part of Marshall Gold Discovery State Historic Park in Coloma, California. A meteorite fall in 2012 landed close to the mill; the recovered fragments were named the Sutter's Mill meteorite.