Quadruple Expansion Engine Piston
A piston system from a quadruple expansion engine showing the movement of steam. Steam first enters the first piston, then expanded into the first intermediate piston. This pushes the piston down, then the steam enters the second intermediate to push the piston up. The steam then enters the low piston, where the steam exits the system.
Derr, Louis Cyclopedia of Engineering (Chicago, IL: American Technical Society, 1911)