Editing Watt steam engine (section)

==Introduction==
In 1698, the English mechanical designer [[Thomas Savery]] invented a pumping appliance that used steam to draw water directly from a well by means of a vacuum created by condensing steam. The appliance was also proposed for draining [[Mining|mines]], but it could only draw fluid up approximately {{Convert|25|ft|round=0.5}}, meaning it had to be located within this distance of the mine floor being drained. As mines became deeper, this was often impractical. It also consumed a large amount of fuel compared with later engines.<ref name="Harvnb|Rosen|year-2012|pp">{{cite book
|title=The Most Powerful Idea in the World: A Story of Steam, Industry and Invention
 |last1=Rosen
 |first1= William
|year= 2012 |publisher = University of Chicago Press
|isbn= 978-0226726342 |pages=137
}}</ref>

[[File:Newcomen steam engine.jpg|thumb|The model [[Newcomen atmospheric engine|Newcomen engine]] upon which Watt experimented]]
The solution to draining deep mines was found by [[Thomas Newcomen]] who developed an [[Newcomen atmospheric engine|"atmospheric" engine]] that also worked on the vacuum principle. It employed a cylinder containing a movable piston connected by a chain to one end of a rocking beam that worked a mechanical lift pump from its opposite end. At the bottom of each stroke, steam was allowed to enter the cylinder below the piston. As the piston rose within the cylinder, drawn upward by a counterbalance, it drew in steam at atmospheric pressure. At the top of the stroke the steam valve was closed, and cold water was briefly injected into the cylinder as a means of cooling the steam. This water condensed the steam and created a partial vacuum below the piston. The atmospheric pressure outside the engine was then greater than the pressure within the cylinder, thereby pushing the piston into the cylinder. The piston, attached to a chain and in turn attached to one end of the "rocking beam", pulled down the end of the beam, lifting the opposite end of the beam. Hence, the pump deep in the mine attached to opposite end of the beam via ropes and chains was driven. The pump pushed, rather than pulled the column of water upward, hence it could lift water any distance. Once the piston was at the bottom, the cycle repeated.<ref name="Harvnb|Rosen|year-2012|pp"/>

The Newcomen engine was more powerful than the Savery engine. For the first time water could be raised from a depth of over {{Convert|300|ft|sigfig=1}}. <ref>{{Cite book | author = Society of Gentlemen | others = Illustrated with above three hundred copper-plates engraved by Mr. Jefferys | year = 1763 | title = A new and complete dictionary of Art and sciences; comprehending all the branches of useful knowledge, with accurate descriptions as well of the various machines, tools, figures and schemes necessary for illustrating them, as of the classes, kinds, preparations, and uses of natural productions, whether animals, vegetables, minerals, fossils, or fluids; together with the kingdoms, provinces, cities, towns and other remarkable places throughout the world | edition = The second edition, with many additions, and other improvements. | publisher = W.Owen | publication-place = London |page=1073 (table)}}</ref>  The first example from 1712 was able to replace a team of 500 horses that had been used to pump out the mine.  Seventy-five Newcomen pumping engines were installed at mines in Britain, France, Holland, Sweden and Russia. In the next fifty years only a few small changes were made to the engine design.

While Newcomen engines brought practical benefits, they were inefficient in terms of the use of energy to power them. The system of alternately sending jets of steam, then cold water into the cylinder meant that the walls of the cylinder were alternately heated, then cooled with each stroke. Each charge of steam introduced would continue condensing until the cylinder approached working temperature once again. So at each stroke part of the potential of the steam was lost.