James Watt’s steam engine was based on that of Thomas Newcomen and Watt improved upon it in many ways:
A separate steam condenser was added, which greatly increased the efficiency of the engine.
An original linkage converted the vertical movement of the piston into circular motion for which there were more industrial applications.
A flyball governor was used to regulate the amount of steam allowed in the engine. This system, combined with a heavy flywheel, made it possible to control the rotation speed.
A new distribution system, which applied steam to both sides of the piston, increased the power of the engine as well as the steadiness of movement.
Watt’s first steam engine dates to 1765. It is estimated that by 1800, he and his partner, Matthew Boulton, had built 500.
The caption reads in the original French:
Machine à balancier de Watt.