Difference engine

Charles Babbage's Difference Engine No. 2 Babbage wanted to end the errors in printed mathematical tables, and the method of differences let him compute a whole table of polynomial values using nothing but addition, which gears do well. He worked on his first engine from 1821, but the project halted in 1832 after a dispute with his engineer, Joseph Clement, leaving a demonstration piece of about 2,000 parts. His improved design of 1848, Difference Engine No. 2, has 8,000 parts, weighs five tons and is 11 feet long. It was never built in his lifetime. In London its calculating section was finished in 1991, for the bicentenary of his birth, and the printer in 2002. The completed machine works as Babbage intended.