Trial piece for Babbage's Difference Engine No 2, 1985-91.
© Science Museum / Science & Society Picture Library
Difference Engine No 2 was constructed by the Science Museum in London from drawings made by the British computing pioneer Charles Babbage (1791-1871) between 1847 and 1849. This trial piece was constructed by the Science Museum to verify the design of the basic adding element. A small section of the calulating part was built to test the basic logic of the design and to explore the manufacturing techniques for the full-scale engine. It is manually operated by lifting and turning the axes from above a fixed sequence, whereas the full-scale machine performs the calculating cycle automatically. Babbage conceived the engine to calculate a series of numerical values and automatically print the results but it was never constructed in his lifetime.