Who developed a practical steam engine?

A steam powered water pump was invented in 1698 by an Englishman, Thomas Savery. In 1712, Thomas Newcomen improved the Savery engine but it was still very inefficient. Then Scottish inventor James Watt improved the Newcomen engine and is credited with inventing the first working steam engine. However steam power was first mentioned by the Greek inventor Hero in Alexandra, Egypt in the first century, AD. It was called the aeolipile and was a simple metal ball that contained water. There were two tubes sticking out on opposite sides of the ball with a 90 degree bend that went in opposite directions. When heated over a fire, the water boiled in the ball and came out the tubes, which made it spin.