Three way brass stopcock

1790-1819 in Birmingham
James Watt

Three-way cock

This item is part of the contents of the workshop that Scottish engineer James Watt developed at his home, Heathfield, at Handsworth, Birmingham. Although Watt is best known for his work on the steam engine, his workshop contains a wide variety of objects from many different projects, from chemistry to sculpture-copying.

The description of the item was written by Edward Collins, the land agent responsible for Heathfield when the workshop was given to the Science Museum in 1924. Collins could not always identify what he was looking at, but always described what he saw clearly. This has allowed his descriptions to form the basis of subsequent research.

This three-way valve appears to have been used as an injection valve with a steam engine. In 1763-64, Watt built a small engine with a wooden cylinder six inches in diameter and capable of making a working stroke twelve inches long. In experiments on steam alongside this engine, Watt used a glass flask and tubes, with the joints between them ‘made tight by lapping that part of the tube with packthread, covered with glazier’s putty.’ The branch of the valve with a jet fixed to its end carries traces of putty. Thought it is by no means certain, the valve sist in the workshop alongside other fragments from Watt’s early experimental work on steam engines, and may be associated with the experimental engine of 1763-4.


James Watt's Garret Workshop
Object Number:
brass (copper, zinc alloy) and complete
overall (estimate): 120 mm x 180 mm x 200 mm, Wt. 0.515kg
  • component - object
  • hardware - component
  • finish hardware
Major J.M. Gibson-Watt