The steam engine consists of a steam piston/cylinder that moves a large wooden beam to drive the water pump. The engine does not use steam pressure to push up the steam piston! Rather, the system is constructed so that the beam is heavier on the main pump side, and gravity pulls down the main pump side of the beam. Weights are added to the main pump side if necessary. The pumps in Figure 1 expel water on a upward pump piston stroke, in agreement with the pumps used in the equipment at the time, and the discussion follows that design. In order to draw water into the main pump on the right side of the diagram, consider a cycle that starts with the beam tipped down on the right. The cylinder below the steam piston is first filled with atmospheric pressure steam and then water is sprayed into the cylinder to condense the steam. The resulting vacuum pulls the steam piston down, pulling the main pump piston upwards, lifting the water above the main pump piston and filling the lower main pump chamber with water. At the bottom of the steam piston stroke, a valve opens to restore the steam cylinder to atmospheric pressure, and the beam tips down on the right by gravity, permitting the main piston to fall. As the main piston falls, the water from below the piston passes to the chamber above the piston as explained later. Atmospheric pressure steam enters the steam cylinder during this step, enabling the process to be repeated.
