The Difference Engine is an
alternate history. The primary premise is that the Babbage Engine was
successfully created and an age of mechanical computers began in the 1830's.
Strong forces favoring industrial progress have gained control of the British
government. Similar progress is taking place in France under Louis Bonaparte.
The events of the book begin in 1855. 20 or so years of rapid progress have brought
us to a point where mechanical computers run mechanical "video"
displays and can print out mug shots selected by the computer as meeting
criteria given by witnesses of crimes. (Being mechanical, the computers
continue to store the data on punch cards.) Along with the earlier
industrialization, there is an earlier onset of pollution problems.
Industrial progress has also
resulted in the existence of coal-fueled road vehicles, a subway in London, etc. Scientific progress has included an earlier adoption of evolution theory.
Some of the events are
influenced by people connected to politics in Texas. This raises other
historical differences. Rather than a Mexican-American War making Texas a part of the US, Texas is an independent country. And the US Civil War seems to
already be in progress.
A great deal of the book is a
presentation of this altered 19th century. However, a thread goes through the
book about a box of punch cards containing a computer program which certain
forces are prepared to use criminal methods to obtain. We first see this box
of punch cards with a character who has a hobby of programming, but Texas politics complicates matters. Then, it appears again with the Prime Minister's
daughter (who was a mathematician). It ends up with a paleontologist,
Mallory. Then, criminal and anarchist forces go after Mallory.
It is suggested the program
caused France's largest computer to need repairs after it was run.
There is a lot of the book
which does not connect to the thread that holds the book together as a novel
rather than being a collection of fragments about this altered 19th century.
These tangents may convey some bits and pieces of the 19th century in general
or this parallel one in particular. However, it seemed to me that even if a
briefer version of these tangents would have been beneficial, the actual long
versions approached the status of filler. One example that comes to mind was
Mallory going back to a prostitute's room. The book gives us the details of
meeting her at a tavern, the journey to where she lived, some description of
their sex (each of three times), the food and drink they each had in between
the sex (each of two times they got refreshments), etc. This seemed more than
necessary, but I told myself it was vaguely possible the prostitute would have
some significance later in the book. However, there was nothing about this
section that played any role later.
The book rests on the premise
of a divergence from our familiar history. The Babble machine is implemented
in the 1820's and developments from there create an entrenched (mechanical)
computer age by the 1850's. This has consequences in other areas. However,
it's not clear whether all the divergences from our history are supposed to be
resulting indirectly from the Babble machine, or whether we are to assume
multiple independent alterations of history. For instance, there are two (or
three) major changes to US history. (1) Texas becomes an
independent country without the US entering into a Mexican-American War.
[Without a Mexican-American War, not only does Texas not become part of the US, but the US does not acquire the western states from Mexico.] (2) At the time of the
book's events (1855), the US seems to already be involved in the Civil War. In
our history, the US Civil War occurred from 1861 to 1865.
In our history, the
Mexican-American War began in 1845. Therefore, the reason the Mexican-American
War didn't occur can't be the Civil War unless the Civil War began by 1845 and
continued through 1855. The change to the Mexican-American War and the Civil
War could have had a common cause. In 1845, Abraham Lincoln was a Congressman
affiliated with the Whig Party. The Whigs opposed the Mexican-American War,
but were a minority. If, for some reason, the Whigs were a majority in 1845,
those changes in the political landscape might have prevented the
Mexican-American War and lead to the Civil War beginning earlier. However, this
is speculation on my part. We are never told exactly when Texas became
independent or when the Civil War began, we’re not told whether the Whigs
control the North in the US, and there is no other clarification on American
politics. It’s possible that pro-industrial forces had changed the course of
American history, as they had in England and France. However, there is no
indication that the South has taken the lead in industrialization, yet the
British has found it politically convenient to support the South in the Civil
War. So we can do little more than guess.