19.14.2 Energy from moving water.
Water flowing in contact with a device a waterwheel is one of oldest sources of power other than humans or animals. Grain mills driven by waterpower existed in ancient Greece and Room, and large waterwheel developing up to 50 hp were contructed im the middle Ages. In colonial North America, waterwheel drove grist mills and sawmills and were further applied to leather, textile, and machine shop operations. Because of problems with low water flow in the summer and ice formation in the winter, these operation were rapidle displaced when steam engines became available in the early 1800s.