The Humphrey pump was patented by HA (Herbert Alfred) Humphrey, a gas engineer and chemist, in 1906. An explosion of inflammable gas and air hitting the surface of the water propels the pump. As a result, the Humphrey pump has been likened to a water cannon. This kind of pump was used at the Cobdogla irrigation settlement on the River Murray. Today, the world's only working Humphrey pump is at the Cobdogla Irrigation and Steam Museum. It can be seen in action four times a year and is known as 'Big Thumper' as the ground shakes with its action. Big Thumper can deposit 1.25 million gallons of water in irrigation channels per hour.