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[[Alexander John Thompson]] about 1927 built ''integrating and differencing machine'' (13-digit numbers and fifth-order differences) for his table of logarithms "Logarithmetica britannica". This machine was composed of four modified Triumphator calculators.<ref>{{Cite book |url=https://books.google.com/books?id=fH48AAAAIAAJ|title=Logarithmetica Britannica: Being a Standard Table of Logarithms to Twenty Decimal Places |last=Thompson |first=Alexander John |date=1924 |publisher=CUP Archive |isbn=9781001406893 |pages=V/VI, XXIX, LIV–LVI, LXV (archive: pp. 7, 30, 55–59, 68) }} [https://archive.org/stream/in.ernet.dli.2015.285845/2015.285845.Logarithmetica-Britannica#page/n29/mode/1up/search/Integrating+and+Differencing+machine Alt URL]</ref><ref>{{Cite web|url=https://history-computer.com/Babbage/NextDifferentialEngines/Thompson.html|title=History of Computers and Computing, Babbage, Next differential engines, Alexander John Thompson|website=history-computer.com|access-date=2017-09-22}}</ref><ref>{{Cite web|url=http://mechrech.info/publikat/publikat.html#pub70|title=Publikationen|last=Weiss|first=Stephan|website=mechrech.info|pages=160–163|others=''Difference Engines in the 20th Century''. First published in Proceedings 16th International Meeting of Collectors of Historical Calculating Instruments, Sep. 2010, Leiden|access-date=2017-09-22}}</ref>
3[[Leslie Comrie]] in 1928 described how to use the [[Odhner Arithmometer|Brunsviga]]-Dupla calculating machine as a difference engine of second-order (15-digit numbers).<ref name=":5" /> He also noted in 1931 that National Accounting Machine Class 3000 could be used as a difference engine of sixth-order.<ref name=":4" />{{Rp|137–138}}
===Construction of two working No. 2 difference engines===
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The printer's primary purpose is to produce [[Stereotype (printing)|stereotype]] plates for use in printing presses, which it does by pressing type into soft plaster to create a [[flong]]. Babbage intended that the Engine's results be conveyed directly to mass printing, having recognized that many errors in previous tables were not the result of human calculating mistakes but from slips in the manual [[typesetting]] process.<ref name="Campbell-Kelly 2004" /> The printer's paper output is mainly a means of checking the engine's performance.
In addition to funding the construction of the output mechanism for the Science Museum's difference engine, [[Nathan Myhrvold]] commissioned the construction of a second complete Difference Engine No. 2, which was on exhibit at the [[Computer History Museum]] in [[Mountain View, California]] from May 2008 to January 2016.<ref name="CHM Press Releases" /><ref>{{Cite web |url=http://www.computerhistory.org/exhibits/babbage/ |title=The Babbage Difference Engine No. 2 |publisher=Computer History Museum |access-date=2018-10-26 }}</ref><ref name="chm2">{{cite web |author-link=Daniel Terdiman |last=Terdiman |first=Daniel |date=April 10, 2008 |title=Charles Babbage's masterpiece difference engine comes to Silicon Valley |url=https://www.cnet.com/culture/charles-babbages-masterpiece-difference-engine-comes-to-silicon-valley/ |work=[[CNET News]]}}</ref><ref>{{Cite web |last=Noack |first=Mark |title=Computer Museum bids farewell to Babbage engine |url=https://www.mv-voice.com/news/2016/01/29/computer-museum-bids-farewell-to-babbage-engine |access-date=2022-07-10 |website=Mv-voice.com }}</ref> It has since been transferred to [[Intellectual Ventures]] in [[Seattle]] where it is on display just outside the main lobby.{{Citation needed|date=June 2023}}<ref>{{Cite web |last=Ventures |first=Intellectual |date=September 1, 2016 |title=IV’s Favorite Inventions: The Babbage Machine |url=https://www.intellectualventures.com/buzz/insights/ivs-favorite-inventions-the-babbage-machine#:~:text=Visit%20the%20Intellectual%20Ventures%20Lab,in%20the%20IV%20Lab%20foyer. |url-status=live |access-date=March 24, 2024 |website=Intellectual Ventures}}</ref>
== Operation ==
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