This document describes the working of a hydraulic ram, which uses water hammer pressure to lift a small amount of water to a higher elevation using the force of a larger volume of flowing water from a higher source. It works by using the kinetic energy of the supply water to close and open valves, pressurizing an air vessel to discharge water into the delivery pipe. The document also defines two types of efficiencies for hydraulic rams - D'Aubuisson efficiency and Rankine efficiency - which calculate the efficiency based on the water flow and head pressures in the supply and delivery systems.