Air enters the aspirator bottle, initially almost filled with water, through a tube inserted through a sealed stopper into the water bath, while the water leaves through a nipple near the bottom of the bottle. This arrangement provides a constant water pressure head, which is equal to the height of the water column between the nipple and the bottom end of the tube. Thus the water jet will have the same range as the water level in the bottle falls from its initial level to the level of the bottom of the tube.
The idea of this gizmo to provide water at a constant pressure, was first proposed by Edme Mariotte, a 17th century French scientist. A device called the Mariotte siphon, making use of this concept, is used in agriculture to provide irrigation at a constant flow rate and as a research tool in determining the properties of soil. His work is also cited in the Catholic Encyclopedia.