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Issue No.03 - July-September (2005 vol.27)
pp: 70-78
ABSTRACT
Charles Babbage designed Difference Engine No. 2 between 1846 and 1848. Contemporary drawings illustrate a machine--never built during his lifetime--that calculates and tabulates polynomials, printing results in hard copy and producing stereotype molds for plates intended for use in conventional printing presses. This article describes construction of the first complete physical realization of a full Babbage engine design and outlines Babbage's ambitions for this advanced engine.
INDEX TERMS
Mechanical computers, computing engines, Charles Babbage, Difference Engines, Difference Engine No. 2, reconstructions, Nineteenth century computing, prehistory of computing
CITATION
Doron D. Swade, "The Construction of Charles Babbage's Difference Engine No. 2", IEEE Annals of the History of Computing, vol.27, no. 3, pp. 70-78, July-September 2005, doi:10.1109/MAHC.2005.45
REFERENCES
1. A. Hyman, Charles Babbage: Pioneer of the Computer, Oxford Univ. Press, 1982, pp. 124-131; D. Swade, The Cogwheel Brain: Charles Babbage and the Quest to Build the First Computer, 2000, Little, Brown (published in the US as The Difference Engine: Charles Babbage and the Quest to Build the First Computer, Viking, 2001, pp. 65-71).
2. A.G. Bromley, "The Evolution of Babbage's Calculating Engines," Annals of the History of Computing, vol. 9, no. 2, 1987, pp. 113-136.
3. The quoted phrase is Henry Prevost's. See H.P. Babbage, ed., Babbage's Calculating Engines: A Collection of Papers by Henry Prevost Babbage, E. and F.N. Spon, 1889, preface. (Reprinted in The Charles Babbage Institute Reprint Series for the History of Computing. vol. 2, Tomash Publishers, 1982. For historical evolution of Babbage's ideas, see B. Collier, The Little Engines that Could've: The Calculating Engines of Charles Babbage,Garland, 1990.
4. For a detailed technical description of the Analytical Engine, see A.G. Bromley, "Charles Babbage's Analytical Engine, 1838," Annals of the History of Computing, vol. 4, no. 3, 1982, pp. 196-217 (reprinted in 1998, vol. 20, no. 4, pp. 29-45). Also see A.G. Bromley, "Babbage's Analytical Engine Plans 28 and 28a— The Programmer's Interface," IEEE Annals of the History of Computing, vol. 22, no. 4, 2000, pp. 4-19.
5. Collier, The Little Engines that Could've, p. 211; also see A.G. Bromley, The Babbage Papers in the Science Museum: A Cross-Referenced List, Science Museum, London, 1991, p. 11.
6. Science Museum Library Babbage Papers , drawing BAB [A] 99, "Rough sketch of an element of a Difference Engine and method of Carrying Consecutively,"1 March 1842.
7. C. Babbage, The Exposition of 1851 or Views on the Industry, the Science, and the Government of England, 2nd ed., 1851; M. Campbell-Kelly, ed., The Works of Charles Babbage, vol. 10, William Pickering, 1989, p. 108.
8. C. Babbage to Lord Derby, 8 June 1852, quoted in C. Babbage, Passages from the Life of a Philosopher, Longman, Green, Longman, Roberts & Green, 1864, p. 104.
9. For quoted phrase see Babbage, Passages from the Life, p. 114. For a technical description of the anticipating carriage mechanism, see A.G. Bromley, "Charles Babbage's Analytical Engine, 1838," Annals of the History of Computing, vol. 4, no. 3, 1982, p. 202 and the following.
10. Babbage Passages, p. 97.
11. Science Museum Library Babbage Papers , drawing BAB [A] 166, "Apparatus for moving Stereotype frames for Analytical & Difference Engines," undated.
12. Babbage Passages, p. 107. See also p. 106 for reference to "imagined obligation."
13. Science Museum Registered File, ScM 2004/46/5 pt. 1, "Babbage Difference Engine No. 2: Project Correspondence." File Note recording first action, 7 Nov. 1986.
14. For the listing, see Bromley, The Babbage Papers, 1991, pp. A-13 to B-3.
15. There are two drafts. The first is dated 13 June 1985. The second is a slightly expanded version dated 27 March 1987; Science Museum Registered File, ScM 2004/46/19, "Babbage Difference Engine Project: Correspondence with Dr. A. Bromley."
16. For a comprehensive description, see D. Swade, Charles Babbage's Difference Engine No. 2: Technical Description, Science Museum Papers in the History of Technology, Science Museum, London, 1996.
17. Science Museum Library Babbage Papers, drawing BAB [A] 172, "End View of Inking Printing Paper and Stereotype Apparatus," undated.
18. A. Bromley to M. Weston, 20 May 1985, Science Museum Registered File, ScM 2004/46/19.
19. For a fuller narrative account of the trial piece, see Swade, C ogwheel Brain, chapter 13.
20. For details of composition analysis see Science Museum Registered File, ScM 2004/46/29, "Babbage DE2: Technical Notes."
21. For a fuller narrative account of the build (excluding the output apparatus), see Swade, Cogwheel Brain, Part III, pp. 221-318.
22. For cam profile details, see the Science Museum Library Babbage Papers, drawing BAB [A] 169, "Plan of Cams for Odd Difference Figure Wheels and for Vertical motion of Even Difference warning."
23. I am indebted to Eiiti Wada for this analogy. Personal communication, Tokyo, 24 July 1998.
24. See Swade, Charles Babbage's Difference Engine No. 2, 1996, pp. 70-71.
25. C. Babbage, On the Mathematical Powers of the Calculating Engine, 1837; M. Campbell-Kelly, ed., The Works of Charles Babbage, vol. 3, William Pickering, 1989, p. 39.
26. M. Lindgren, Glory and Failure: The Difference Engines of Johann Muller, Charles Babbage, and Georg and Edvard Scheutz, 2nd ed., MIT Press, 1990.
27. Based on the earlier Analytical Engine designs, Bromley first estimated the speed of calculation for Difference Engine No. 2 at one result every 7 seconds. He later amended this to 3.5 seconds. See Ref. 15.
28. For discussion of digit precision in the context of contemporary table-making, see D. Swade, Calculation and Tabulation in the 19th Century: Airy versus Babbage, doctoral dissertation, 2003, Univ. College London. For a summary account and use of Difference Engine No. 2, see D. Swade, "The 'Unerring Certainty of Mechanical Agency'": Machines and Table Making in the Nineteenth Century," The History of Mathematical Tables: From Sumer to Spreadsheets, M. Campbell-Kelly et al., ed., Oxford Univ. Press, 2003, pp. 143-174.
29. F. Spufford, "The Difference Engine and The Difference Engine," Cultural Babbage: Technology, Time and Invention, F. Spufford and J. Uglow, eds., Faber and Faber, 1996.
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