A mill is a device, often a structure, machine or kitchen appliance, that breaks solid materials into smaller pieces by grinding, crushing, or cutting. Such comminution is an important unit operation in many processes. There are many different types of mills and many types of materials processed in them. Historically mills were powered by hand or by animals, working animal, wind (windmill) or water (watermill). In modern era, they are usually powered by electricity.
A tabletop hammer mill
Principle of SAG Mill operation
Table top hammer mill
A windmill in Kuremaa, Jõgeva County, Estonia
A horse mill is a mill, sometimes used in conjunction with a watermill or windmill, that uses a horse engine as the power source. Any milling process can be powered in this way, but the most frequent use of animal power in horse mills was for grinding grain and pumping water. Other animal engines for powering mills are powered by dogs, donkeys, oxen or camels. Treadwheels are engines powered by humans.
Donkey mill at La Alcogida Ecomuseum in Fuerteventura
Horse or donkey-powered stone mills at Pompeii.
The Horse Mill at Wester Kittochside Farm near Glasgow
A bullock-powered mill, Seychelles