James Watt ( January 19 , 1736 - August 19 , 1819 ) was a Scottish mathematician and engineer . James Watt , FRS , FRSE ( 19 January 1736 â `` 25 August 1819 ) was a Scottish inventor and mechanical engineer whose improvements to the Newcomen steam engine were fundamental to the changes brought by the Industrial Revolution in both the Kingdom of Great Britain and the world .