Dear All I am pleased to report that the full technical description of Charles Babbage's Difference Engine No. 2 has recently been made available online on open access by the Science Museum (London). The Engine was built to Babbage's original drawings (1847-1849) and completed in 2002. It has 8,000 parts, weighs 5 tonnes, and works as Babbage intended. It is the first of Babbage's calculating engines to be built in its entirety. Over the decades-long life of the project I documented the interpretation of the 19th-century drawings, the design decisions made in its construction, its assembly, operational debugging, and what was learned from running the Engine for countless live public demonstrations. A full description of the Engine is presented in two works available online: <https://www.sciencemuseum.org.uk/sites/default/files/2023-09/DE2_Technical_ Description.pdf> Difference Engine No.2 Technical Description (232 pages, 131 illustrations) Provides a detailed interpretation of Babbage's design, and documents the technical understanding that informed the successful construction of the working machine. <https://www.sciencemuseum.org.uk/sites/default/files/2023-08/User_Manual_PD F_Vsn_1.1_Final_SEC1.pdf> Difference Engine No.2 User Manual (147 pages, 199 illustrations) Documents the practical procedures for operating the Engine safely, setting up a calculation, testing, trouble-shooting, fault-finding, and maintenance including lubrication. The two documents are free-standing i.e. relevant drawing-excerpts are embedded in the text so that understanding does not, for the most part, rely on reference to the full 19th-century design drawings. Direct Browser Links: Technical Description: https://www.sciencemuseum.org.uk/sites/default/files/2023-09/DE2_Technical_D escription.pdf User Manual: <https://www.sciencemuseum.org.uk/sites/default/files/2023-08/User_Manual_PD F_Vsn_1.1_Final_SEC1.pdf> https://www.sciencemuseum.org.uk/sites/default/files/2023-08/User_Manual_PDF _Vsn_1.1_Final_SEC1.pdf Additional Material <https://collection.sciencemuseumgroup.org.uk/documents/aa110000003/the-babb age-papers> The Babbage Papers at the Science Museum: * Digitised archive of Babbage papers including full technical archive and Notebooks. https://collection.sciencemuseumgroup.org.uk/documents/aa110000003/the-babba ge-papers <https://www.sciencemuseum.org.uk/objects-and-stories/charles-babbages-diffe rence-engines-and-science-museum> Charles Babbage's Difference Engines and the Science Museum | Science Museum * Short contextual and historical summary. * Links to the Technical Description and User Manual are in Further Reading. https://www.sciencemuseum.org.uk/objects-and-stories/charles-babbages-differ ence-engines-and-science-museum Citation: Swade, Doron, Charles Babbage's Difference Engine No. 2: Technical Description. Science Museum, 2023. Swade Doron, Charles Babbage's Difference Engine No. 2: User Manual. Science Museum, 2023. Best wishes Doron Swade