An early calculator designed by Charles Babbage and subsidized by the British government. Employing wheels and rods, which others had experimented with earlier, the project was started in 1821 but failed its test in 1833. Babbage then turned his attention to the Analytical Engine and completely abandoned the Difference Engine by 1842. Although never completed, it did improve the precision of Britain's machine-tool industry. In 1991, the National Museum of Science and Technology built a working model of the Difference Engine.
In 1879, Babbage's son reassembled a section of the Difference Engine from parts, and in 1995, Christie's auction in London auctioned off that section to the Power House Museum in Sydney for $282,000. The other known sections are owned by Harvard and Cambridge Universities. See Analytical Engine
The Difference Engine
This impression from a woodcut was printed in 1853 showing a portion of the Difference Engine that was built in 1833. Babbage later turned his attention to the Analytical Engine. It, too, was never finished. (Image courtesy of Charles Babbage Institute, University of Minnesota, www.cbi.umn.edu)