Bryan Donkin - Career - Difference Engine

Difference Engine

In 1829, Charles Babbage requested Donkin's assistance with George Rennie (engineer), in investigating the ownership of intellectual property, tooling and piece-parts of the difference engine, whose manufacture had been commissioned by Babbage from Joseph Clement.

In 1857 the British government authorized the sum of £1200 for a full-scale difference engine with attached printing apparatus based on the design of Per Georg Scheutz and his son Edvard to be constructed by Donkin's company, which had acquired a reputation for building machines for the colour printing of banknotes and stamps. Costs overran and Donkin delivered the machine in July 1859, several weeks past the deadline, incurring a loss of £615.

Despite the engine's printing unit working badly, the Royal Society and the Astronomer Royal were generally positive when they inspected it on August 30, 1859, expressing their satisfaction at its construction. Donkin was unhappy that he had lost so much money on the project, which he attributed to the engine's unexpected intricacy and the fact that he had had very little to base his original cost estimate on, Edvard Scheutz having given him very little information. In addition, costly machine tools had had to be made specially to make the engine's components and many alterations had been introduced along the way.

The machine was used by William Farr at the General Register Office to compute life tables, which were published in 1864. It operated on 15-digit numbers and 4th-order differences, and produced printed output just as Charles Babbage had envisaged. This machine is now in the London Science Museum.