Editing Steam engine (section)

===High-pressure engines===
The meaning of high pressure, together with an actual value above ambient, depends on the era in which the term was used. For early use of the term Van Reimsdijk<ref>"The Pictorial History of Steam Power" J.T. Van Reimsdijk and Kenneth Brown, Octopus Books Limited 1989, {{ISBN|0-7064-0976-0}}, p. 30</ref> refers to steam being at a sufficiently high pressure that it could be exhausted to atmosphere without reliance on a vacuum to enable it to perform useful work. {{harvnb|Ewing|1894|p=22}} states that Watt's condensing engines were known, at the time, as low pressure compared to high pressure, non-condensing engines of the same period.

Watt's patent prevented others from making high pressure and compound engines. Shortly after Watt's patent expired in 1800, [[Richard Trevithick]] and, separately, [[Oliver Evans]] in 1801<ref name="Thomson 2009">{{cite book |title     = Structures of Change in the Mechanical Age: Technological Invention in the United States 1790–1865
 |last      = Thomson
 |first     = Ross
 |year      = 2009
 |publisher = The Johns Hopkins University Press
 |location  = Baltimore, MD
 |isbn      = 978-0-8018-9141-0
 |page      = [https://archive.org/details/structuresofchan0000thom/page/34 34]
 |url       = https://archive.org/details/structuresofchan0000thom/page/34
}}</ref><ref>{{Citation
  |last=Cowan |first=Ruth Schwartz|author-link=Ruth Schwartz Cowan
  |title=A Social History of American Technology
  |publisher=Oxford University Press |place=New York
  |year=1997
  |page=74
  |isbn=978-0-19-504606-9
}}</ref> introduced engines using high-pressure steam; Trevithick obtained his high-pressure engine patent in 1802,<ref>{{cite book|last1=Dickinson|first1=Henry W|last2=Titley|first2=Arthur|title=Richard Trevithick, the engineer and the man|year=1934|publisher=Cambridge University Press|location=Cambridge, England|page=xvi|chapter=Chronology|oclc=637669420}}</ref> and Evans had made several working models before then.<ref>The American Car since 1775, Pub. L. Scott. Baily, 1971, p. 18</ref> These were much more powerful for a given cylinder size than previous engines and could be made small enough for transport applications. Thereafter, technological developments and improvements in manufacturing techniques (partly brought about by the adoption of the steam engine as a power source) resulted in the design of more efficient engines that could be smaller, faster, or more powerful, depending on the intended application.{{sfn|Hunter|1985|p=}}

The [[Cornish engine]] was developed by Trevithick and others in the 1810s.{{sfn|Hunter|1985|pp=601–628}} It was a compound cycle engine that used high-pressure steam expansively, then condensed the low-pressure steam, making it relatively efficient. The Cornish engine had irregular motion and torque through the cycle, limiting it mainly to pumping. Cornish engines were used in mines and for water supply until the late 19th century.{{sfn|Hunter|1985|p=601}}