Few inventions have affected human history as much as the steam engine. Without it, there would have been no locomotives, no steamers and no Industrial Revolution. The power the steam engine supplied was closely tied to the changes in technology, culture and economy that took place in much of the Western world during the late 18th and early 19th centuries.
The steam engine was not the product of a single stroke of genius. Instead it developed gradually, as many inventions do, from the work of numerous people. In Greece, Hero of Alexandria built a device that used steam to produce rotation as early as the 1st century AD, but he did not intend it to be a practical device for generating power. Other steam-powered devices appeared in other parts of the world in later centuries, but most were little more than curious marvels until the 17th century. In the 1670s, a Frenchman Denis Papin built a sort of primitive pressure cooker he called a steam digester. After several accidental explosions, Papin added a steam release valve to the device. While watching the rhythmic action of the valve, Papin envisioned an early steam engine. Though he never built one, English inventor Thomas Savery adopted Papin’s ideas to build an engine for a water pump.
Savery’s pump exploited both atmospheric pressure and steam pressure. Savery generated the latter by forcing steam produced by a boiler into an empty chamber, which was showered with cold water to condense the steam and produce a vacuum inside the chamber. The creation of the vacuum pulled water up through a pipe. Savery designed the machine to pump water from mineshafts, but it performed inconsistently. Another Englishman, Thomas Newcomen, developed an improved steam engine and water pump around 1710. Unlike Savery’s design, the Newcomen engine included a moveable piston, a feature that significantly enhanced the engine’s power. With it, miners could pump water from depths of 150 feet or more.
The machine was the first engine to gain widespread use. By the mid 1700s, Newcomen engines could be found at mines in France, Sweden, Russia, Britain and other countries. Yet the engine had its problems. Most significantly, it was costly to run because it required large amounts of coal to produce the heat that turned water into steam. Also, the same cylinder into which the boiler transferred steam served as the location of condensation; as a result, the engine wasted a lot of heat. This heat was used just to get the cylinder, after it had been cooled with jets of water, back up to a high enough temperature to stop automatic condensation of new steam entering the chamber.
In the 1760s, someone finally developed a way to eliminate this problem, making the steam condensing engine more efficient, faster and more powerful. While working at a university in Glasgow as an instrument maker, James Watt was asked to fix a Newcomen engine. Examining the engine, Watt came to the conclusion that it wasted too much heat. He realized that by adding a separate condensing chamber to the engine, it would be much more efficient. Instead of heating and then cooling a single chamber over and over again, the engine Watt envisioned would keep one cylinder always hot so that it could receive steam from the boiler, and the second cylinder always cool so that the steam passed to it from the first chamber would condense into water. This water could then be drawn off and recycled for use by the boiler.
Despite the potential of his design, Watt did not find it easy to make it a reality. He had to borrow money to build a small prototype, then needed a partner to actually create a product that he could sell. In 1768, he and John Roebuck began a joint venture, and the following year Watt patented his design of an engine featuring a discrete chamber for condensing steam. The pair, however, did not get very far. Watt began working as a land surveyor to pay the bills and Roebuck went bankrupt in 1772. To pay off a debt, Roebuck gave his share of Watt’s invention to Matthew Boulton, an English manufacturer. Lucky for Watt (and the rest of the world), Boulton proved a much better entrepreneur than Roebuck. With Boulton’s help, Watt perfected a practical version of the engine, which they first produced for sale in 1775.
Watt’s engine used only about 25 to 30 percent of the fuel required of a Newcomen engine. Still, Boulton knew people who already owned Newcomen engines might not want to buy an entirely new one. He came up with the idea of licensing the separate condenser technology to these customers in return for a portion of the money they saved each month on fuel costs. Soon steam engines with separate condensers became the standard. As Watt and others improved the engine’s design in subsequent years, new uses arose. Before long, steam became synonymous with industrial power, and industrial power drove the West into its future.