Harnessing the power of steam marked a significant step in technology. The introduction of the steam engine led to many new inventions, most notably in transportation and industry. Steam engines transfer the energy of heat into mechanical energy, often by allowing steam to expand in a cylinder equipped with a movable piston. As the piston moves up and down (or alternatively, from side to side), an attached arm converts this motion into parallel motion that drives a wheel. Models of the steam engine were designed as early as 1690, but it was not until 70 years later that James Watt arrived at the design of the modern steam engine.
Steam engines also improved significantly.
In early steam engines, steam from the boiler was directed to a cylinder, where it drove the movement of a single piston before it was expelled. These single-expansion engines wasted some of the steam's energy. More efficient double-expansion engines used the steam expelled from one cylinder to power another cylinder. By 1873 even more efficient triple-expansion engines came into use.