How did James Watt improve Thomas Newcomen's steam engine?

Answer 1

Newcomen's engine was heated with steam being admitted to it, then the cylinder was cooled causing the steam to condense, creating a vacuum that drew the piston down, driving a pump. Watt improved upon this by building a separate condenser to keep from heating and cooling the cylinder, which caused thermal stress and cracking. Later with the help of Matthew Boulton they designed an engine that used the power of the steam itself (rather than a vacuum) to drive the piston in both directions, creating the first double acting engine.