thumb|A replica of Trevithick's engine at the National Waterfront Museum in Swansea, Wales In 1784, James Watt, a Scottish inventor and mechanical engineer, patented a design for a steam locomotive. Watt had improved the steam engine of Thomas Newcomen, hitherto used to pump water out of mines, and developed a reciprocating engine in 1769 capable of powering a wheel. This was a large stationary engine, powering cotton mills and a variety of machinery; the state of boiler technology necessitated the use of low-pressure steam acting upon a vacuum in the cylinder, which required a separate condenser and an air pump. Nevertheless, as the construction of boilers improved, Watt investigated the use of high-pressure steam acting directly upon a piston, raising the possibility of a smaller engine that might be used to power a vehicle. Following his patent, Watt's employee William Murdoch produced a working model of a self-propelled steam carriage in that year.
thumb|a replica of trevithick's engine at the national waterfront museum in swansea wales in 1784 james watt a scottish inventor and mechanical engineer patented a design for a steam locomotive watt had improved the steam engine of thomas newcomen hitherto used to pump water out of mines and developed a reciprocating engine in 1769 capable of powering a wheel this was a large stationary engine powering cotton mills and a variety of machinery; the state of boiler technology necessitated the use of low-pressure steam acting upon a vacuum in the cylinder which required a separate condenser and an air pump nevertheless as the construction of boilers improved watt investigated the use of high-pressure steam acting directly upon a piston raising the possibility of a smaller engine that might be used to power a vehicle following his patent watt's employee william murdoch produced a working model of a self-propelled steam carriage in that year