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Portrait of The steam engine

General knowledge · Inventions & discoveries

The steam engine

1712 (Newcomen); 1769 (Watt's patent)

Invention — power and industry

The machine that turned heat into work was not invented once but improved in stages: Thomas Savery's pump of 1698, Thomas Newcomen's atmospheric engine of 1712, which drained mines at enormous cost in coal, and James Watt's separate condenser, conceived in 1765 and patented in 1769, which roughly quadrupled efficiency. With Matthew Boulton's Birmingham money and salesmanship, Watt's engines drove mills, mines and factories; Richard Trevithick's high-pressure engines then made steam mobile, and the railway age followed.

How to spot them

  • ▸Draining Cornish tin and Midlands coal mines; the beam engine and its rocking beam
  • ▸A separate condenser, so the cylinder need never be cooled — the idea that made it efficient
  • ▸Boulton and Watt of the Soho Manufactory, Birmingham; the Lunar Society
  • ▸Two units named after two of the men involved: one SI, one stubbornly imperial

Key facts

Thomas Savery's 'The Miner's Friend' of 1702 (1698–1702)

His patent of 1698 described an engine 'for raising water by fire'; its broad wording blocked rivals for decades

Thomas Newcomen's atmospheric engine of 1712 (1712)

Steam condensed inside the cylinder and air pressure pushed the piston down; hugely wasteful of coal, but it worked for 60 years

An idea that came to James Watt on Glasgow Green in 1765 (1765)

Keep the condenser separate, so the cylinder stays hot; patented in 1769 and extended by Act of Parliament to 1800

The sun-and-planet gear, used to turn up-and-down motion into rotation (1781)

Watt's alternative to the crank, which was already patented by a rival

Trevithick's Penydarren locomotive of 1804 (1804)

The first to haul a load on rails, in south Wales, using the high pressure Watt thought too dangerous

Boulton's boast to Boswell: 'I sell here, sir, what all the world desires to have — power' (1776)

Matthew Boulton, showing James Boswell round the Soho Manufactory

Hero of Alexandria's aeolipile, a spinning ball of the first century AD

A toy rather than a machine, but the earliest known device driven by steam

Key ideas

  • Newcomen's engine works by vacuum, not pressure: condensing steam makes a partial vacuum and the atmosphere does the pushing, which caps the power available
  • Watt's separate condenser saves the heat wasted in reheating a cylinder that has just been cooled to condense the steam — a fuel saving of roughly three-quarters
  • High pressure, pioneered by Trevithick and Oliver Evans, raises power for a given size, which is what makes a portable engine possible

Quick-fire facts

  • •Thomas Savery patented his engine in 1698; Thomas Newcomen's first known working engine was erected in 1712, near Dudley in the West Midlands
  • •James Watt (1736–1819) was an instrument maker at the University of Glasgow, repairing a model Newcomen engine when the idea came to him
  • •The SI unit of power, the watt, is named after him; so is the horsepower, which he defined for marketing purposes as 33,000 foot-pounds per minute
  • •Watt was a member of the Lunar Society of Birmingham alongside Boulton, Erasmus Darwin, Josiah Wedgwood and Joseph Priestley
  • •The centrifugal governor, adapted by Watt to hold engine speed steady, is a classic early example of feedback control
  • •Watt's patent was so broadly drawn and so vigorously enforced that it is often blamed for delaying high-pressure steam in Britain
  • •Richard Trevithick's Penydarren engine of 1804 won a 500-guinea wager by hauling iron and passengers about nine miles
  • •Stephenson's Rocket won the Rainhill Trials in 1829, with a multi-tube boiler and blastpipe
  • •Watt appeared on the Bank of England fifty-pound note alongside Boulton from 2011 until its withdrawal

Drill it — 10 cards

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Sources