The principle of the steam engine

The steam ship burns coal in a furnace which heats up water in a boiler, turning the water into steam. This steam has a great expansive power, and is directed into a cylinder. This is basically a strong metal tube which contains a piston which is free to move along the tube as it is pushed by the expanding steam. A system of valves regulates when steam from the boiler is admitted to the cylinder, and also when it is released (or exhausted) to allow the piston to travel back along the cylinder ready for another stroke. The piston is connected to a system of rods which turn a shaft. The shaft is arranged so that it turns paddle wheels or a propellor (also known as a screw) to drive the ship along.

The first steam ships

A practical steam engine was built by Newcomen in 1712, but historians argue over when and where steam was first used to propel a vessel. A number of inventors and developers in the USA and Europe undoubtedly contributed to the steam ship. As the renowned Victorian naval architect John Scott Russell wrote, ‘the creation of the steamship appears to have been an achievement too gigantic for any single man.’

It is generally agreed that the first demonstration that a steam-driven ship could make a voyage in exposed waters involved Henry Bell’s steamer Comet, which sailed from Glasgow down the River Clyde in 1812. From that date, steam ships began to carry fare-paying passengers and cargo along estuaries and across relatively short stretches of water, for instance between England or Scotland and Ireland, and across the English Channel. Independence from wind and tide meant that steam ships could offer sailings to a fixed timetable, and virtually guarantee the crossing time: something the sailing ship operator could never do with any confidence.