Thursday, June 21, 2012

Babbage's Siege Engine



The title of this blog, Machinamenta, means basically the same thing as another Latin word, machina. They both mean "machine," but there are a few kinds of machines that machina is used for most often. One of those is siege engines, the huge contraptions wheeled up to a castle gate or wall to try to breach it.
In 1823, Charles Babbage was trying to get the government to fund development of his computer. This was a very unusual idea at the time, and the politicians were uncomfortable with it, wondering what they would be expected to fund next.
The prime minister, Robert Peel, wrote in a letter "'Aut haec in nostros fabricata est machina muros.  Aut aliquis latet error.' I should like a little consideration before I move in a thin house of country gentlemen, a large vote for the creation of a wooden man to calculate tables from the formula x^2+x+41. I fancy Lethbridge's face on being asked to contribute."
The Latin quote is from the Aeneid, where Laocoon is urging the Trojans not to accept the wooden horse that the Greeks have built into into the walls of Troy: 'It is an engine set against our walls... or some other trickery lies hidden within.' Peel is saying that the difference engine is a siege engine, bringing change that is far too strange for the 'country gentlemen' in Parliament to be willing to support. 
(The formula he mentions will be a familiar one to anyone who has ever played with finding patterns in prime numbers. The difference engine was able to calculate tables of results for any second degree polynomial using the method of differences, a technique that only requires successive additions.)