Newcomen's steam engine

The story

Mines full of water

At the start of the 18th century, in England, more and more coal was being dug. Wood, which for centuries had been used to heat houses and to run forges and furnaces, was becoming scarce because forests were being cut down so fast; coal, plentiful under the ground in that country, was replacing it. But there was a big problem. When miners went deeper, the tunnels filled with water seeping out of the rock. To keep digging, the water had to be pumped out all the time.

This was done with human arms or with horse power, the horses walking round in circles to work the pumps: a slow and very expensive job. In many mines, sooner or later, it became impossible to dig any deeper, and the coal seams were left unused. More powerful machines were needed.

The blacksmith from Dartmouth

Thomas Newcomen was a blacksmith and ironmonger from Dartmouth, a port in Devon, in the south of England. He sold tools to the miners of Cornwall, the neighbouring county, and knew their problems at first hand. He was not a scientist and had not been to university, but he was good with his hands and full of ideas. Together with a friend who was a plumber, John Calley, he spent more than ten years experimenting with a machine that used steam.

Some things were already known: in 1698 a military engineer, Thomas Savery, had patented a steam pump called “the miner's friend”, but it worked badly and could explode. The French physicist Denis Papin, a few years earlier, had thought of a cylinder with a piston moved by steam. Newcomen brought these ideas together in a much safer and more practical machine.

How it worked

Newcomen's machine had a big boiler, in which water was boiled, and an upright cylinder with a piston that could slide up and down. The steam, at very low pressure, flowed into the cylinder and pushed the piston up. Then a jet of cold water made the steam condense, which means it turned back into tiny drops of water: inside the cylinder a partial vacuum formed, and the pressure of the outside air, like an invisible hand, pushed the piston down with great force. That is why the machine was called “atmospheric”. The piston was joined by a chain to an enormous wooden beam, which swung like a seesaw and worked the pump that drew water from the mine.

1712: the first machine at work

The first Newcomen engine we know of for certain started work in 1712 at a coal mine near Dudley Castle, in the Midlands. It made about twelve strokes a minute, and with every stroke it lifted a large amount of water from a depth of about fifty metres: more work than dozens of horses, day and night, without ever getting tired. It was huge and noisy, a great brick building with the wooden beam swinging above it, and it burned an enormous amount of coal, but in coal mines, where fuel was never short, that did not matter.

Because Savery's patent, which covered every machine for raising water with fire, was still in force, Newcomen had to join forces with him and share the profits, so he never became rich. He was a deeply religious man, a lay preacher in the Baptist church, and he never knew how much his invention would change the world.

Success came quickly. By the time Newcomen died, in 1729, more than a hundred engines were already working, in Britain and on the Continent: in France, Germany, Hungary and Sweden. In the second half of the 18th century hundreds had been built: they pumped water out of coal and tin mines and out of towns, and lifted water to turn the waterwheels of factories.