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''The Difference Engine'' is a 1990 {{alternate history}} novel written collaboratively by Creator/WilliamGibson and Creator/BruceSterling. It is a prime example of the {{steampunk}} sub-genre, often considered the GenrePopularizer.

It posits a {{Victorian Britain}} circa 1855 in which a great wave of technological and social change has occurred after entrepreneurial inventor Charles Babbage succeeded in his ambition to build a mechanical computer (actually his analytical engine rather than the difference engine). Among the many various changes that arise as a result of this innovation are an even more powerful [[TheBritishEmpire British Empire]], a DividedStatesOfAmerica, an early Communist Revolution in Manhattan led by Karl Marx himself, steam-powered gurneys (this timeline's equivalent of cars), and the premature invention of "camphorated cellulose" (what we know as plastic).

The story follows Sybil Gerard, a political courtesan and daughter of an executed Luddite leader (she is borrowed from Creator/BenjaminDisraeli's novel ''Sybil''); Edward "Leviathan" Mallory, a [[AdventurerArchaeologist paleontologist and explorer]] who comes into a lot of money thanks to a good bet on an advanced steam gurney model; and Laurence Oliphant, a historical figure with a real career, as portrayed in the book, as a travel writer whose [[CovertGroupWithMundaneFront work was a cover for espionage activities]] "undertaken in the service of Her Majesty".

Linking all their stories is the trail of a mysterious set of reportedly very powerful camphorated cellulose computer punch cards and the individuals fighting to obtain them; as is the case with special objects in several novels by Gibson, the punch cards are to some extent a MacGuffin.

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!!Tropes present in this work include:

* AIIsACrapshoot
* AdventurerArchaeologist: Mallory is a GentlemanAdventurer Archaeologist.
* AluminumChristmasTrees: During the London riots, Mallory sees a team of steam-engines of Crimean War fame pulling artillery guns. In RealLife, [[http://en.wikipedia.org/wiki/Traction_engine the traction engine]] had already been in production for farm and circus caravan use by the 1850s, it would have been trivial to adapt them to pull guns and [[http://steamtraction.farmcollector.com/multimedia/image-gallery.aspx?id=42364&seq=7 at least one of them operated in Crimea]].
** The [[http://en.wikipedia.org/wiki/Great_Stink Great Stink]] also took place in real life, just three years later and minus the riots.
* AssholeVictim: The in-universe Duke of Wellington was a tyrant who massacred hundreds and later thousands of his own countrymen, claiming he would destroy "Jacobinism" by all means.
* AwesomeMcCoolname: Edward "Leviathan" Mallory, so named after the dinosaur he discovered. He doesn't much like the nickname.
* BadassBookworm: Edward Mallory is quite capable of beating up and / or shooting anyone in a fair fight. Oh, and he also discovered the largest dinosaur ever and continental drift.
* BigBrotherIsWatching: the Eye.
* BunnyEarsLawyer: This version of Ada is a hopeless sex and gaming addict and a bit out of her mind (though it she might have been drugged, [[WhatHappenedToTheMouse that part's never explained]]).
* ChekhovsGun: Mallory notes an AwesomeButImpractical 'machine-carbine' which is rather inaccurate; at the end of his story Captain Swing empties a magazine from one at him, [[ATeamFiring only to miss completely]] and fall to a single aimed shot from Mallory's buffalo rifle.
* ClockworkCreature: a literal BambooTechnology automaton from Oliphant's Japanese visitors.
* CoitusEnsues: Mallory abruptly has a romantic fling with Hetty, going so far as to abandon the recently injured Ebenezer Fraser to do so. [[spoiler:This detour is largely why he gets trapped in London in the wake of the riots.]]
* DarkSecret: Sybil hints in the final chapter the assassination of the Duke of Wellington had been instrumented by the Rads themselves and performed by the Brotherhood of Sappers and Miners. Cue the said Brotherhood to be the wealthiest workers' guild through the next 2 decades, always getting the best public works contracts and being most leniently treated when they do a strike...
* DecoyProtagonist: Mick and Sybil
* DirtyCommies: The Manhattan commune, lead by no one else but Karl Marx
** RedScare: Subverted and ridiculed to death - the speeches of the [[NinjaPirateZombieRobot revolutionary Marquess]] and Captain Swing himself are [[DeliberateValuesDissonance deliberately]] out of touch with reality: no sane man would listen to a Communist-anarchist ''who owns Black slaves'', the working classes would not be interested to support Communism if they have careers to upheld and "brotherhoods" to protect themselves (the supporters of the revolution are mostly thieves and bandits), the idea that "evil capitalists" would gladly shoot human hostages and protect the goods in the warehouse proves to be just as idiotic in-universe as anyone would think, "the temperance speaker" is a murderer herself.
* DividedStatesOfAmerica: The CSA became independent, as did Texas, California, the Manhattan commune, and Britain is playing "divide et impera".
* EmperorScientist: The merit Lords, including Brunel, Darwin, Babbage and several other famous Victorian scientists.
** Also AristocratsAreEvil: The Radical Party removed the old aristocratic class from power and eliminated the ancient titles of nobility, replacing all of them with "Lord", be it by birth or by merit.
* TheEndingChangesEverything
* {{Fanservice}}: in-story. The clock Mallory buys has an allegoric depiction of Science, Progress and Britain. The latter is, for some reason, wearing almost nothing. Other examples include the Americans' theater and the artists on Montmartre (described as "dressed... erm, undressed similarly to each other").
* FelonyMisdemeanor: Fellatio, etc.
** Since it's Victorian England, wearing a skirt so short it shows one's lower leg when she bends over is treated in-story like if she wore a mini-skirt that doesn't cover her panties.
** DeliberateValuesDissonance: Sterling and Gibson jump from allusions to female scientific (Lady Ada) or craftsman's (seamstresses to Engine-punchers) careers to the fact it was scandalous for an unescorted woman to ride the subway - which is at the same time uncanny and even worse when one thinks of certain Middle Eastern countries...
* FictionalPoliticalParty: The Industrial Radical Party, who believe in scientific endeavor, industrial progress, and meritocracy, appointing peerages to "savants".
* FootnoteFever: to let the average writer read the book properly without wondering "Who the hell ''are'' those people?!"
* ForbiddenFruit: The sheer possibility of receiving a fellatio makes Mallory shiver with delight after all the fantasies about it.
* GenreDeconstruction: the original concept was to see how {{Cyberpunk}} themes would work in a historical setting.
* GenrePopularizer: SteamPunk
* GoodPeopleHaveGoodSex: Kind of. Lord and lady Byron have BDSM sessions and so on, while Mallory and Hetty had a very romantic night. On the other hand, Mallory's night with an Indian widow is very much FanDisservice, for himself included.
* HandCannon: Brian's "not exactly regulation" Russian pistol.
* HoldYourHippogriffs / CallARabbitASmeerp: Many modern concepts are expressed through real and made up XIX era slang. "Clackers" instead of "hackers" with cyberpunk-like genre built around them; kinotropes instead of movie projectors, television, rotating billboards, etc.
* HookerWithAHeartOfGold: Cybil and Hetty, albeit in different ways. Cybil'd been forced into that lifestyle and quit it as soon as she got the chance, Hetty is easy-going, very much enjoys sex (something that almost never happens with prostitutes) and is into prostitution only because it pays okay, unlike singing / dancing / posing which she also dabbles in.
* LegacyCharacter: Captain Swing.
* [[{{UsefulNotes/Socialism}} Libertarian Socialism]]: The solution to the worker vs state clashes of the RealLife 1830s was to let the trade unions evolve into uniformed guilds ("brotherhoods") which own property, tooling and industrial patents and which hire their men (with skills and tools) to businesses for significant amounts of money.
* Creator/LordByron: is Prime Minister. Yeah.
* JiveTurkey: Sterling and Gibson go to great effort into fitting the British slang of the time into the story, an effort which might have been wasted:
** "Sand-hog" for underground construction worker is an ''American'' slang word first heard in the ''1870s''.
** "Dollymop" for prostitute is a late 19th century word.
** "Navvy" for road construction worker is a 20th century word, in the 1850s it designated a railway or canal construction worker.
* PeoplesRepublicOfTyranny: The Government claims to be liberal, in practice it holds files on most citizens, blackmails, hangs political opponents and asks from everyone, Mallory included, to declare publicly their allegiance to the party.
* PrettyFlyForAWhiteGuy: The Japanese quartet can be described as extreme reverse weaboos, since they love everything western so much they want to get rid of the Japanese language.
* RichardNixonTheUsedCarSalesman: With Byron as Prime Minister, Creator/BenjaminDisraeli is most famous for his romance novels (he [[AluminumChristmasTrees did write a couple]] in RealLife, including ''Sybil'' from which the Sybil Gerard/Charles Egremont storyline is taken)
* RotatingProtagonist: Sybil Gerard, then Edward Mallory, then Laurence Oliphant.
* SchizoTech: Played [[RealityIsUnrealistic realistically]]. Tom and Brian Mallory built a racing steam-car in the shape of [[TheThirties the 1930s]] streamlined racing cars, but due to the huge fuel consumption of steam engines they needed to take a coal wagon in tow to drive from Sussex to London. Even the most primitive gasoline engines in RealLife only took a couple of gallons of fuel for the same route.
* ScienceMarchesOn / TechnologyMarchesOn: Many examples in-story.
* ShownTheirWork
* [[ShowSomeLeg Show Some Ankle]]: Hetty also lifts her skirt when Mallory asks.
* SteamPunk
* TwiceToldTale: "Dandy Mick", Sybil and the Charles Egremont storyline are taken from Benjamin Disraeli's ''Sybil''.
* UnbuiltTrope: It's hardly the first literary example of the genre, but much is made of the flaws and ValuesDissonance of Victorian England.
* {{Unperson}}: Erasing people from the database does more or less that. Subverted in that it's a good thing for some (Sybil started her life anew, for one), though it's still an effective threat for law abiding gentlemen.
* VeryLooselyBasedOnATrueStory: Disraeli's romantic stories. Also, whatever lies "Captain Swing" spreaded about Mallory, but that's to compromise his reputation. Also applies the book itself (see below)
* WhatIf ...Charles Babbage had completed his Difference Engine (and gone on to build the Analytical Engine)?
* WitchHunt: The hunt for 'Luddite conspirators' by Charles Egremont.
* [[ManBehindTheMan Woman Behind The Man]]: Lord Byron, dashing hero and exceptional public speaker, is uncovered in the appendices after his death as a rather incompetent administrator, pushed and manipulated in political decision by Lady Annabella Byron, who rants on having to endure "his beastly habits" for decades. Victorian Age [[NoWomansLand being what it was]] the position brought little profit to her.

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