The steam engine inventor was James Watt who issued a patent for his invention in 1769.
James Watt was born in Scotland in the little town of Greenock on the banks of the Clyde in 1736. At the age of sixteen he had a short 2 year apprenticeship working for a mechanic / mathematical instrument specialist.
After his short apprenticeship Watt moved to London where he gained employment as a mathematical instrument maker. However, after a severe cold he returned home after an absence of little more than a year.
At this point Watt was appointed to the college of Glasgow as a mathematical instrument maker to the university. It was here at the university that Watt began to experiment with how steam might escape when contained within a tight syringe. This action led to a basic piston that was able to raise quite a considerable weight of 15lbs.
Overtime further experiments were made to improve on this discovery. For example the steam was cooling too quickly so materials were used that would conduct heat more slowly.
Ultimately Watts experiments led to an idea that struck him, that if a communication was opened between a cylinder containing steam, and another vessel which has been exhausted of air and other fluids, then the steam as an expandable fluid, would immediately rush into the empty vessel, and continue to do so until it had established an equilibrium; and if that vessel was to be kept very cool by an injection or otherwise then more steam would continue to enter until the whole was condensed.
Watt further perfected this idea by adding a pump that extracted any water, air and uncondensed steam. Next Watt surrounded the cylinder by a casing to assist the retention of the heat. A piston rod worked through an aperture used the elasticity of the steam from the boiler to impel the piston down the cylinder and all this ultimately led to Watts steam engine.