James Watt (1736-1819), Scottish engineer and inventor, historical artwork. Watt made numerous practical improvements to the steam engine of his day. By 1790 the superior Watt steam engine had completely replaced the older Newcomen variety. His inventions included the double acting engine where the piston is made to both push and pull (1782) and the pressure gauge (1790). He also adopted the centrifugal governor to regulate the speed of a steam engine and coined the term inshorsepowerins to describe a unit of energy. Watt's innovations, coupled with the business acumen of his partner Matthew Boulton, made him a huge financial success.