By Eric Preston

Who invented the steam engine ? It was not James Watt who is widely credited with this, but Thomas Newcomen.

The first practical and successful steam engine, installed in over 1400 locations by 1800, was designed by Thomas Newcomen (1664-1729), a Dartmouth ironmonger and blacksmith. After 1775 the Newcomen design was improved by James Watt, but it was Newcomen who deserves the credit for an engine ‘that changed the world’, providing power to pump water from coal mines – and other applications- throughout the world. This led to greatly increased availability of coal, and the wide application of steam engines in factories and elsewhere. Thomas Newcomen has therefore been called a Father of the Industrial Revolution.

In 1963 the Newcomen Society of London wanted to create a suitable memorial to commemorate the 300th anniversary of Newcomen’s birth, and were able to acquire an original engine dating from 1725, then sited at the Hawkesbury Junction of the Coventry Canal, and move it to Dartmouth. Study of this engine showed that the wooden beam and cylinder were original, although the valve gear had been replaced and a ‘pickle-pot’ condenser had been added below the main cylinder later in the 18th century. This was to improve efficiency by condensing the steam away from the main cylinder, avoiding a wastage of heat caused by water cooling the main cylinder. This greatly improved the engine’s efficiency. James Watt’s engines were designed with a separate condenser after 1775, for the same reason.


With the agreement of Dartmouth Corporation the Memorial Engine was set up in a building formerly an electricity sub-station in Dartmouth’s Royal Avenue Gardens, and officially opened on 24 June 1964. A hydraulic mechanism has been added to allow the engine to be set in motion without the use of steam.


The Memorial Engine is now administered by the Dartmouth Tourist Information Centre, and can be accessed through the TIC office. It is believed to be the only Newcomen Engine that can still be seen in operation, apart from the replica engine at the Black Country Museum, Dudley.

Dartmouth’s Newcomen Memorial Engine

Dartmouth’s Newcomen Memorial Engine, showing the wooden beam with arches. Photo: Eric Preston, July 2011.

The first Newcomen engine for which documentary evidence is available was installed in 1712 at the Conygree Coal Works near Dudley Castle in Staffordshire. It made use of atmospheric pressure as well as steam, and was consequently called an ‘atmospheric engine’. Many other similar engines followed, including one installed in 1725 at Griff Colliery near Coventry. It is this engine (according to Dr. Cyril Boucher of the Newcomen Society) that can be seen operating at the Newcomen Engine House in Dartmouth, Devon.

These first engines were installed under a patent obtained by another Devon engineer, Thomas Savery, which covered the use of atmospheric pressure and condensed steam to pump water from mines. He called this method “raising water by the impellant force of fire”. However Newcomen’s engines, unlike Savery’s, used a vertical cylinder with a piston, whose movement was transmitted to the mine pump by a large wooden beam. Whereas Savery’s engine had not been successful in practice, Newcomen’s was reliable and soon became widely used, with 125 engines installed worldwide by 1733, and over 1400 by 1800.

Principle of Newcomens Atmospheric Engine

The ‘atmospheric engine’ works as shown in the Figure above (click for the fullsize version). The open-ended brass cylinder is mounted directly above a boiler. Steam is allowed into the cylinder by opening a valve, and then condensed by a cold water jet fed into the cylinder. This condenses the steam rapidly, causing the piston to be forced down by the atmospheric pressure above. This movement is transmitted to the mine by a large wooden beam pivoted in the centre and connected to both the piston and the vertical rod operating the mine pump by chains. The weight of the pump rod draws the piston back up the cylinder ready for the next stroke. The valves were operated automatically by levers worked by the movement of a ‘plug rod’ attached to the moving beam. The steam pressure was kept low to avoid leakage.

Diagram of First Newcomen Engine by Henry Beighton 1717

Diagram of First Newcomen Engine by Henry Beighton 1717

The first engine worked at 12 strokes per minute and had 5.5 horse-power, raising 10 gallons of water from a depth of 150 feet at each stroke. Various minor improvements were made as experience was gained, but this design remained basically unaltered for over 60 years.


Grateful thanks are due to the following :-

  • Mr. Clive Lusby of Markham Grange Steam Museum, for permission to print the diagram showing the Principle of the Newcomen engine
  • Mr. Brian Parker of Dartmouth Museum, for the map showing the location of the Dartmouth Memorial Engine.

Further Reading

  1. The Steam Engines of Thomas Newcomen, by L.T.C.Rolt and J.S.Allen, 1977 (ISBN 0 903485 42 7)
  2. The Pumping Station at Hawkesbury Junction, by Cyril T.G.Boucher, 1963 (Transactions of Newcomen Society Vol. 35)
  3. Thomas Newcomen, Engineer 1663/4-1729, by H.W.Dickinson 1929, revised 1989, pub. by The Newcomen Society, Abbot Litho Press Ltd, Newton Abbot.
  4. Thomas Newcomen of Dartmouth and the Engine that Changed the World, by E.J.Preston, 2012, pub. by Dartmouth and Kingswear Society and Dartmouth History Research Group (ISBN 1-899011-27-7).