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Object Name: numerical ring from Babbage's first difference engine
Date: 1822-1834
Inventory Number: 1991-1-0001b
Classification: Calculating Machine
Subject: mathematics
Maker: Charles Babbage
1791 - 1871
Maker: Henry Prevost Babbage
1824 - 1918
Cultural Region: England
Dimensions: 1.9 x 6 x 6 cm (3/4 x 2 3/8 x 2 3/8 in.)
Materials: German silver
Description: This is the silver-metal numerical ring that was once part of Charles Babbage's first difference engine. Made of German silver, it is engraved with numerals.

The ring would have shown a single digit of a larger, multi-digit numeral. It accompanied the posts, gears, and toothed wheels that were assembled by Charles Babbage's son, Henry P. Babbage to illustrate the mechanism for addition used by his father in his first difference engine designed in 1822.

Signed: unsigned
Historical Attributes: This portion of Charles Babbage's first difference engine is not a piece of the whole (which was never completed) but an assembly of parts from the 1822 design. Babbage went on to design a second engine even as he tinkered with the first design until 1834. The project was partially funded by the British government.

When the project was abandoned in 1842, the fragments were sold by the British government as waste metal. Babbage bought some for his own use. Upon his death in 1871, these parts were passed on to his son, Henry Prevost Babbage.

In 1886, Major-General Henry Prevost Babbage put some of the parts together to illustrate the process of addition. H. P. Babbage sent several such assemblies to a number of universities. Letters in the University Archive detail this gift to Harvard.

On March 13, 1997, this instrument was picked up from Howard H. Aiken Computation Lab along with other instruments. The instruments were transferred to CHSI by Edward P. Jackson, Facilitites Manager in the Division of Engineering and Applied Sciences. They originally were on exhibition in the entrance area adjacent to IBM Mark I computer on the first floor of the Aiken Lab.
Provenance: Charles Babbage; Henry P. Babbage; gift to Harvard in 1886.
Related Works: Science, 252 (1991): 1370-1371.

Scientific American, February 1993, pp. 8-91.

Michael Lindgren, Glory and Failure: The Difference Engines of Johann Muller, Charles Babbage, and Georg and Edvard Scheutz (Stockholm: Royal Institute of Technology Library, 1987).
Published References: I. Bernard Cohen, "Babbage and Aiken: With Notes on Henry Babbage's Gift to Harvard, and to Other Institutions, of a Portion of His Father's Difference Engine," Annals of the History of Computing, 10 (1988): 171-193.
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