It is impossible to simply state the facts concerning the eighteenth-century research relevant to the discovery of the composition of water. Henry Cavendish found the liquid to be acid to the taste and identified a small quantity of 'nitrous acid' in the water. The laboratory of Joseph Black and James Watt, at Glasgow, was concerned in various ways with the heating of water, and especially with what they would call changes of state. Charles Gillispie provides a classic example of the positivist treatment of the discovery of the composition of water in the Chemical Revolution. The interpretation of the experiments on water is, as when Cavendish reverted to phlogiston as imponderable in the 1784 phlogiston theory deployed to account for the experiments in which water was produced. Watt's work on the composition of water was part of a 'Scottish School' of chemical work deriving from, but also in some ways departing from, the work of Black.