Like many other modern inventions, the steam engine had a long evolution. It was first conceived of by Greek scientist Hero of Alexandria in the first century A.D. The mathematician invented many “contrivances” that were operated by water, steam, or compressed air. These included not only a fountain and a fire engine, but the steam engine. Many centuries later, Englishman Thomas Newcomen (1663–1729) developed an early steam engine (about 1711) that was used to pump water. He was improving on a previous design, which had been patented by another inventor in 1698.

But it was Scottish inventor James Watt (1736–1819) who substantially improved Newcomen’s machine, patenting his own steam-powered engine in 1769. It was the first practical steam engine, and Watt’s many improvements to the earlier technology paved the way for the use of the engine in manufacturing and transportation during the Industrial Revolution (c. 1750–c. 1850); Britain was just on the cusp of this new age when Watt patented his engine. The steam engine was eventually replaced by more efficient devices such as the turbine (developed in the 1800s), the electric motor (also developed in the 1800s), the internal-combustion engine (first practical engine built in 1860), and the diesel engine (patented 1892). Nevertheless, James Watt’s steam engine played a critical role in moving society from an agricultural-to industrial-based economy. Watt’s legacy also includes the use of “horsepower” and “watts” as units of measure.