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“Difference Engine No. 2

Charles Babbage designed this mechanical calculating machine, called Difference Engine No. 2 between 1847 and 1849. He aimed to print mathematical tables that were much more accurate than the hand-produced versions available to Victorian engineers, scientists and navigators.

Babbage called his machine a Difference Engine because it calculated tables of sums automatically using the method of finite differences. This mathematical method involves only addition and subtraction, and avoids multiplication and division, which are more difficult to mechanise.

Difference Engine No. 2 required three times fewer parts than Babbage’s original Difference Engine, for the same calculating power. Part of the Difference Engine No. 1 is on display in the Making the Modern World gallery on the ground floor.

But, like his other Engines, Difference Engine No. 2 was not completed during Babbage’s lifetime. Find out how this machine was constructed on the other side of the case.”


“Charles Babbage completed the design for this mechanical calculating machine, called Difference Engine No. 2 in 1849. But the machine itself was not built until over 150 years later.

In the 1980’s, a Science Museum team reviewed Babbage’s designs and built Difference Engine No. 2 – the world’s biggest mechanical calculator. Its 4000 cast-iron, steel and bronze components were manufactured to the engineering standards of Babbage’s day.

The Engine made its first error-free calculation in 1991, 200 years after Babbage’s birth. At every fourth turn of the handle – about every 6 seconds – the machine calculates a result up to 31 digits long.

In 2002, the Science Museum added the 4000-part printing mechanism, completing Babbage’s original vision. The project proved that Victorian engineering methods could have achieved Babbage’s aim, and that economic and political issues, combined with Babbage’s difficult temperament, were the main reasons for failure.”


Portsmouth's motto is 'Heaven's Light Our Guide' - the Sun and Moon used to guide ships by sextant and logarithm's which Babbage's Arithmetic Engine tried to calculate. There are two copies of the Engine. One in the Science Museum, South Kensington, London; and the other is owned by Paul Allen, co-founder of Microsoft and Multi-Billionaire. He also finances Spaceship-1, a craft that goes to the edge of the Earth's atmosphere where it's passengers are weightless for a period of 4 minutes.

Difference Engine Blueprint

Difference Engine No. 2 & Webmaster

Difference Engine No. 2

Difference Engine No. 2