In engines, a steam engine is a heat engine whose working substance is water. [1] A steam-engine is now generally understood an engine in which the elasticity or expansive force of steam is used as the moving-power; just as the weight or impulse of water is in the water-wheel, or the pressure of the wind in a windmill. In some of the earlier engines of this kind, it was really the pressure of the atmosphere that was the motive-power, steam being employed merely as a means of producing a vacuum through its rapid condensation, and thus allowing the pressure of the atmosphere to come into play. [5]

Early proto-type history
The first proto-type steam engine was said to have been invented in circa 250BC by Greek compressed air engineer Ctesibius. These came to be known as the ‘aeolipile’ as described by both Roman architect Vitruvius (15BC) and Greek physicist Hero (50AD). [6] Owing to the fact that Hero was the first to give a detailed account on how to make an aeolipile, the device has since come to be known as Hero's engine or the aeolipile of Hero.

In 1543, Spanish captain Blasco de Garay is said to have demonstrated a steamboat of his own invention in the harbor of Barcelona. It has been argued that Garay's engine was an aeolipile type of engine, in which steam produces rotatory motion by issuing from orifices, as water does in Barker's mill. [7]

A rudimentary impact steam turbine was described in 1551 by Arabian engineer Taqi al-Din, who described a method for rotating a spit by means of a jet of steam playing on rotary vanes around the periphery of a wheel.

The preacher Mathesius, in his sermon to miners (Nuremberg, 1562), prays for a man who 'raises water by fire and air’, showing the early application of steam-power in Germany; and the German engineer, SoL de Caus, in the service of the Elector Palatine in Heidelberg, describes, in his work, Lea liaisons dts Forces Mom-antes avec Diverses Machines (Frankfort, 1615), a steam-machine, which was merely a contrivance for forcing the water contained in a copper ball through a tube by applying heat.

In 1629, Italian engineer, Giovanni Branca, invented a sort of steam windmill, in which the steam being generated in a boiler was directed by a spout against the flat vanea of a wheel, which was thus set in motion.

In England, among the first notices we have of the idea of employing steam as a propelling force, is that contained in a small volume, published in 1647, entitled The Art of Gunnery, by Nat. Nye, mathematician; in which he proposes to 'charge a piece of ordnance without gunpowder,' by putting water instead of powder, ramming down an air-tight plug of wood, and then the shot, and applying a lire to the breech untill it burst out suddenly.

In 1648, a device for a steam driven rotating a spit was described by John Wilkins.

In 1655, Marquis of Worcester, in his Century of Inventions, describes a steam-apparatus by which he raised a column of water to the height of 40 feet. This, with the exception of Blasco's, was said to have been the first really useful application of steam; the others had been mere toys.

In 1683, Samuel Morland submitted a project to Louis XIV for raising water by means of steam, accompanying it with ingenious calculations and tables.

Modern piston and cylinder history

See main: Timeline of thermodynamics, Engine development timeline

In 1645, in an effort to disprove Greek philosopher Parmenides's 485BC postulate that nature abhors a vacuum (horror vacui), German engineer Otto Guericke invented piston and cylinder (1645), vacuum pump (1647), and the Magdeburg hemispheres (1654); and with these instruments, Guericke showed that it was possible, manually, to create a vacuum or to remove the air from a sealed volume.

Guericke’s vacuum pump was first described in the book 1657 book Mechanical Hydraulic Pneumatics by German scientist Gaspar Schott, a correspondent of Guericke. Two thinkers who took great interest in this publication were Dutch mathematical physicist Christiaan Huygens and English physicist and chemist Robert Boyle who read the book. Boyle assigned his assistant and his assistant Robert Hooke the job of making an improved Guericke's air vacuum design, which he did in 1658, albeit one that also functioned as a pump.

In the decades to follow, Huygens began working with French engineer Denis Papin to make various piston and cylinder gunpowder engines, with various amounts of success. The biggest hurdle to these gunpowder engines was that they became fouled quickly and failed to make a so-called "perfect vacuum", but instead would only make a partial vacuum, yielding a limited amount of work.

Out of this effort, in 1679 Papin made a pressure cooker or bone digester, which could turn almost anything solid into the liquid state and then into the gaseous state. Early designs exploded, after which a pressure release valve was introduced. It is said that by watching this pressure release valve bob up and down that Papin conceived of the steam engine. Papin would go on to detail the outline of piston and cylinder steam engine in his 1690 memoir "A New Method to Obtain Very Great Motive Powers at Small Cost", in which a liquid put inside of the cylinder was first put in contact with a hot body (fire) and made to expand, then put in contact with a cold body (stream of river water), a quickly made vacuum would be created that would drive the piston down in such a manner that if the process was repeated, in a cyclical manner, useful work could be obtain.

In the years to follow, so it is said, English engineer Thomas Savery learned of Papin's designs and in 1698 he obtained a patent what became to be known as the Miner's friend, a sort of sump pump, that was the first working modern steam engine. In 1699, Savery exhibited a working model of his invention before the Royal Society. Savery, in pumping mines, made use of the condensation of steam in a close vessel to produce a vacuum, and thus raise the water to a certain height, after which the elasticity of steam pressing upon its surface was made to raise it still further in a second vessel.

In 1705, English engineer Thomas Newcomen took out a patent for what he called an "Atmospheric Engine", a type of modified more-functional Savery engine, and by 1712 had working models. [3]

In the latter half of the 18th century, Scottish engineer James Watt add on a number of inventions and design improvements to the functionality of the steam engine, including: separate condenser (1765), sun and planet gear (1781), the fly-ball governor (1788), the indicator (1796) and "indicator diagram", made with his employee John Southern, which tracked the changes in volume of the piston, the definition of "pony power" (or horse power).

Thermodynamics
The physics underlying the operation of the steam engine, specifically the understanding of how fire (or heat) creates cyclical mechanical movement (up and down piston movement), through its actions on an intermediate substance (water), is the basic science of thermo-dynamics, initiated with the 1824 publication Reflections on the Motive Power of Fire by French physicist Sadi Carnot.

The “veritable creators” of the steam engine, starting with Savery and Newcomen, according to Carnot, are English engineer John Smeaton, who made an improved Newcomen engine (1775), Scottish engineer James Watt, who made a number of improvements to the Newcomen engine, such as the separate condenser (1765), sun and planet gear (1781), centrifugal governor (1788), and indicator diagram (1796), English engineer Arthur Woolf, who designed an improved boiler for producing high pressure steam (1803) and invented a compound steam engine (1805), and English engineer Richard Trevithick who built the first steam engine automobiles (1801).

In each of these various heat engines, Carnot presumed that the key to their operation was the "re-establishment of equilibrium in the caloric". The theory was later proven false by German physicist Rudolf Clausius who, beginning in 1850, corrected this supposition with the mathematical argument of "increase in entropy" in the cycle. [4]

References
1. Carnot, Sadi. (1824). Reflections on the Motive Power of Fire - and on Machines Fitted to Develop that Power. Paris: Chez Bachelier, Libraire, Quai Des Augustins, No. 55.
2. Galloway, Robert L. (1881). The Steam Engine and its Inventors. London: MacMillan and Co.
3. Savery, Thomas. (1702). The Miner's Friend – or an Engine to Raise Water by Fire, [URL]. London.
4. Clausius, R. (1865). The Mechanical Theory of Heat – with its Applications to the Steam Engine and to Physical Properties of Bodies. (Google Books). London: John van Voorst, 1 Paternoster Row. MDCCCLXVII.
5. Anon. (1868). Chamber’s Encyclopedia : a Dictionary of Universal Knowledge, Volume 9 (section: Steam engine, 99-103). Publisher.
6. (a) Vitruvius. (15BC). On Architecture, Chapter VI (paragraph 2). Publisher.
(b) Hero. (date). Pneumatica (aeolipile). Alexandria: Publisher.
(c) Ctesibius – Wikipedia.
7. (a) Gale, Leonard. (1838). Elements of Natural Philosophy (Barker’s mill, pg. 89). Collins, Keese, & Co.
(b) Barker’s mill – Britannica.