Student Essay

Water Power

Three WaterWheels.
Courtesy of Slater Mill Historic Site, Pawtucket, RI.

Water power was the prime mover of the Industrial Revolution. Waterwheels used the power of water running downstream in a river to turn machinery. However, water power was nothing new. Water-powered devices had been used, even in some textile processes, for nearly two thousand years. Mills mechanized a number of very tedious tasks. Waterwheels powered grist mills for grinding grain into flour, saw mills for carving lumber out of logs, fulling mills for finishing cloth, and twisting mills for winding silk thread. Neither animals nor people could match the economy and tireless power of water.

The reliance upon water power to run the machinery of the new factories meant that factories had to be built upon a river. Yet not every place upon the river made a good factory site. The best location was where the level of the river dropped to provide more power. Because there are a limited number of good mill sites on each river, a potential mill site was valuable and costly.

Thomas Sweeny III and Robert Howard, Typical Mill Site.
Courtesy of the Hagley Museum, Wilmington, DE.

To develop water power on a site, the millwright commonly built a dam to store water at the highest point above the mill and a channel, called a mill race, to direct the water to the waterwheel and to carry it back to the river. Damming the river to collect water in the mill pond often interfered with fishing, farming, and boat travel. So the new water-powered factories often came at the expense of other members of the community who had previously relied upon the river for their own livelihood and convenience.

The use of water power also had consequences for the organization of the factory. Because it was difficult to transmit the mechanical energy of the waterwheel over long distances, the factory was located by the riverside. To keep the manufacturing close to the power, mill owners often built two-and-three story factories and transmitted the power by gearing to the upper floors. A central power source like the waterwheel encouraged entrepreneurs to bring the new machinery, raw materials, and workers to one location, an organization which had the additional advantage of greater control over production.

Thomas Sweeny III and Robert Howard, Undershot Wheel.
Courtesy of the Hagley Museum, Wilmington, DE.

The development of the mechanized factory led to efforts to improve the efficiency of existing water power technologies. A British engineer named John Smeaton analyzed the relative efficiency of two forms of waterwheels, the undershot and the overshot. The average overshot wheel was far more efficient than the undershot, about 65% as opposed to 25%. The undershot wheel is an impulse wheel, since the water imparts its energy by pushing. If the hillside is steep, the water moves fast at the bottom and can push impressively against the paddles of an undershot wheel. The overshot wheel is a gravity wheel. It is a series of buckets attached to the outside of a big circle. The water goes into a container at the top and drops all the way down. The ability to capture more power from a descending river allowed mills to proliferate and in turn further encourage the development of water-powered technologies.

Thomas Sweeny III and Robert Howard, Overshot Wheel.
Courtesy of the Hagley Museum, Wilmington, DE.

The growth of mills was accompanied by the growth in the power of waterwheels. From the first half of the 18th-century to the first half of the 19th-century, the average horsepower increased 300% to 12-18 horsepower. The largest wheels were 60 and 70 feet in diameter and capable of producing upwards of 250 horsepower. Taking advantage of America's abundance of wood, most waterwheeels were constructed of wood. Usually, only the bearings and the gear teeth were made of metal. However, wooden wheels needed replacement roughly every ten years. When American millowners' waterwheels no longer functioned, they could choose to install turbines instead of new waterwheels. This difference may have had a large role in the Americans' far more rapid adoption of the newest form of waterwheel, the turbine, at midcentury.

Water produced the largest part of industrial power until after the Civil War. In 1790 there were some 7,500 small mills in the United States. In 1825 Maine, New Hampshire, Vermont, and New York had about 16,000 mills. By 1850 some 60,000 mills existed, scattered all across the country. Most of these mills were grist and sawmills, operating seasonally as demand and water were available. Others were part of large mill complexes that made textiles and other manufactured goods. Not until the 1870s did most textile factories begin to use steam power and then only a few years later many turned to electric power. The first part of the American Industrial Revolution was powered by water.

Copyright © 1998 The Lemelson Center for the Study of Invention and Innovation, National Museum of American History, Smithsonian Institution. All rights reserved.

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Last Revision: 6/5/98