On 14 June 1822 Charles Babbage presented to the Royal Astronomical Society his proposal for a machine capable of automatically calculating and tabulating mathematical functions via the method of finite differences. The Difference Engine was not programmable — it was designed for a single task: repeatedly adding to produce tables of polynomial values, eliminating human errors in calculating astronomical and mathematical tables. Although Babbage never finished it in his lifetime, the London Science Museum built Difference Engine No. 2 in 1991 following his original plans: it worked without errors. The Difference Engine is the first link in the chain leading to modern computing, and its limitation — being a single-purpose calculator — is exactly what motivated Babbage to conceive the Analytical Engine.