© Science Museum/Science & Society Picture Library
The figure shows the only completed portion of the engine, assembled by Babbage's engineer Joseph Clement in 1832. It represents about one seventh of the calculating mechanism of the planned full size engine. The portion shown has nearly 2,000 individual parts and is one of the finest examples of precision engineering of the time.
© Science Museum/Science & Society Picture Library
In 1985 the Science Museum in London decided to build Difference Engine 2 to original designs for the bicentennial of BabbageÕs birth in 1992. Completed in November 1992, the first operational Babbage differential engine is made of bronze, iron and steel , 3.6 m long, 2.3 m tall, weighs three tons, cost around $500,000 and took a year to assemble. It has seven orders of difference and calculates to 31 figures. The photo shows the difference engine with Doron Swade, Curator at the Science Museum.
In 1993 the newly constructed Difference Engine was raced with a Canon BJ Notebook BN22, the first notebook computer with built-in bubble jet printer. The difference engine did not have a printer, so a chime was sounded each time a result was computed.
The difference engine produced nine 31 digit results before the notebook bubble jet began printing. After that the notebook produced 50 results in a little more time the difference engine needed to produce its next result.
In January 1998 Nathan Myhrvold, chief technology officer at Microsoft, agreed to pay $375,000 for the construction of a printer for the difference engine if the Science Museum would build him an identical machine and printer to decorate his Washington home. As a consequence Difference Engine 2 now produces its calculations in hard copy.
Science Museum (2004) Babbage. http://www.sciencemuseum.org.uk/on-line/babbage/ (accessed 29 August 2004)