The Watts steam engine was the first type of steam engine to make use of steam at a pressure just above atmospheric to drive the piston helped by a partial vacuum. Improving on the design of the 1712 Newcomen engine, the Watt steam engine, developed sporadically from 1763 to 1775, was the next great step in the development of the steam engine. Offering a dramatic increase in fuel efficiency, the new design replaced Newcomen engines in areas where coal was expensive, and then went on to be used in the place of most natural power sources such as wind and water. James Watt's design became synonymous with steam engines, due in no small part to his business partner, Matthew Boulton.