The study of the properties of fluids, hydrostatics, was an important section in most courses on experimental philosophy. Fountains of varying constructions and containers with different liquids would be used to visualise the properties of fluids.
The central fountain in the image below is an instrument used to demonstrate the expansion of air by heat. As the air expands it pushes up a jet of water. To create a jet of fire Nollet recommends the use of eau de vie instead of water, lighting the jet with a candle once it exits the vase, as shown to the left.
The illustrations below relate to a range of experiments using water-containing vessels and immersed objects. Scales are used to investigate what happens when a hollow object is placed in water, while glass tubes are submerged in a vase containing coloured liquid in order to show the water level under different circumstances.