Sunday, February 4, 2024

January 2024 Analytical Engine Project Report

Project Report to Computer Conservation Society Committee for meeting 18 January 2024

Work continues apace on defining which of Babbage’s Analytical Engine designs would be meaningful to build. Tim Robinson’s extensive description and analysis of Babbage’s range of designs provides the stimulus and knowledge-base for this process. Len Shustek and Tim have been digging deeper into the algorithms and mechanical design implementation of some of Babbage’s computational processes. Their experiences are both sobering and heartening. Heartening because these are the conversations we have been waiting to have. Sobering because of the complexity of what is involved in reverse engineering detailed intention and algorithmic principles from the mechanisms depicted in the drawings and their accompanying notations.  

Specifically, Tim and Len have been examining Plan 27 and Plan 28a, two advanced Babbage designs, for their viability as a build target. One outcome has been Tim’s written analyses of the levels of completeness of each of these Plans. A collateral prize has been a piece of bibliographical reconstruction to inform understanding of Plan 27. The Buxton papers held at the History of Science Museum, Oxford, contain material Babbage wrote in Florence in 1841 while he was working on Plan 27. The Buxton manuscripts are unsympathetically bound: folios are out of order, contain revisions, and material in the gutters of the spine is difficult to read. Tim has revisited the images of these manuscripts, and our transcriptions of them, to reconstruct the likeliest linear account from the patchwork quilt of the primary sources. He writes that ‘the result turns out to be one of the most coherent pieces he [Babbage] ever wrote on the Engine.’  

Devices Len and Tim have explored include the anticipating carriage mechanism, the method of division and the operation of the barrels used for ‘microprogramming’. The anticipating carriage was an early breakthrough for Babbage who wrote that the invention ‘produced an exhilaration of the spirits which not even [his host’s] excellent champagne could rival’. Len has been experimenting with algorithmic simulations, component-level simulations, and some 3D printing. These investigations deepen and extend understanding. They also agitate and inform an ongoing debate about trade-offs between manufacturing costs, historical fidelity and what is practically realisable in a foreseeable timescale.  

Reflecting on Babbage’s failure to complete any of his engines Babbage’s son wrote:

The History of Babbage's Calculating Machines is sufficient to damp the ardour of a dozen enthusiasts.

Major-General H. P Babbage, 12 September 1888.

I wonder if we can prove him wrong.

Doron Swade

Friday, September 29, 2023

Autumn 2023 report to the Computer Conservation Society

Project Report to Computer Conservation Society Committee for 21 September 2023

The omission of regular reports is not indicative of a drop in activity. Quite the opposite. My last report signalled a turning point: Tim Robinson’s panoramic and detailed technical description of Babbage’s designs for the Analytical Engine put us in a position, for the first time, to specify what would be meaningful to build.

In March last year I reported that we needed to expand the team to include expertise that we did not have – primarily solid modelling and mechanical engineering, and the report was an invitation, a call, a plea, for expressions of interest to take the project forward. We have had a promising response. Len Shustek, Chairman Emeritus of the Board of Trustees of the Computer History Museum, picked up the gauntlet and set about engaging with Tim’s technical description of the AE and assessing options for going forward. This exploratory collaboration has been a welcome relief to Tim who has been working for the last six years in near-complete isolation. Discussions are ongoing about the algorithms Babbage proposed for computational process, the prospective role of various forms of simulation, and criteria of authenticity in our design of apparatus where Babbage’s provisions are less than complete. Discussions are ongoing about how to finesse the balance between fidelity to the original designs and their practical feasibility. Moving to implementation invokes issues of funding, project management, intellectual ownership, and hosting the eventual build.

Since the last report Tim has expanded the knowledge-base with an extended account of Babbage’s Mechanical Notation – Babbage’s quasi-mathematical language of signs and symbols that he used to describe mechanisms and their operation. Tim’s description includes the historical development of the Notation and Babbage’s use of it in his engine designs, especially for the Analytical Engine about which practically nothing has been published. The account runs to 16,000 words which extends the length of the overall account to some 140,000 words, a treatise that ranks as a defining treatment to date of Babbage’s work on calculating machines.

So the knowledge base is sound and provides an unprecedentedly well-founded platform for implementation.

Just over 200 years ago Babbage wrote:

Whether I shall construct a larger engine of this kind, and bring to perfection the others I have described, will in great measure depend on the nature of the encouragement I may receive.

- (Charles Babbage to Sir Humphrey Davy, 3 July 1822).

Doron Swade

Friday, March 17, 2023

Spring 2023 report to the Computer Conservation Society

Project Report to Computer Conservation Society Committee for 16 March 2023

It has been a while. So, a brief recap on where we are and what we propose to do.


The mission of the project is to build a Babbage Analytical Engine for historical and educational purposes. Babbage left no single definitive design for an Analytical Engine. Instead there are drawings (called Plans) Babbage drafted to record developmental staging posts as his ideas evolved over a period of some 40 years. We regard an understanding of these Plans, and the design trajectory they represent, as a prerequisite of what could meaningfully be built i.e. which signature features of which design we should combine to create a machine that would best convey Babbage’s conception of an automatic digital general purpose computing machine in the 19th century. 

In November 2021 I reported that Tim Robinson in the US had had completed the most comprehensive description yet of the Analytical Engine. The work is a product of five years research founded on a detailed review of the entire Babbage technical archive. The work analyses the workings, design and development of the machine, with a running evaluation of levels of conception, completeness, and of mechanical detail. The account runs to some 120,000 words and describes six phases of development from 1832 till Babbage’s death in 1871. 

Since then, Tim has extended the analysis with a description of the Selecting Apparatus, a key feature of how Babbage implemented division using the selection of multiples of the divisor to be subtracted from the dividend to determine each next digit of the quotient. The description of the designs and their development, adds some 6,300 words to the earlier account. With the addition of this description, the whole account positions us to finally advance the project to the next stage – specifying what to build.

Way Forward

We need to expand the team to include expertise we currently do not have: animation and modelling skills for simulating mechanisms, and that of mechanical engineers. In February 2022 we sought to grow the team by inviting a promising party to engage and collaborate with Tim to develop and refine the account so that it could serve as an induction and briefing document for new team members, and as the foundational reference source for design and construction. By October 2022 it was evident that this first recruiting attempt had not ignited. 

Putting in the time and effort into preparing Tim’s account for release into the public domain would have the significant benefit of capturing and preserving the substantial advances in understanding, allowing it to serve as a launching pad for subsequent implementation. Preparing the treatise for publication for use by others would well serve both history and Babbage studies but would delay implementation by several years. The loss of momentum this would entail is a significant concern.

We need to attract new people committed to the mission of building a Babbage Analytical Engine and motivated to engage in the technical design challenges. We then need to attract resources to fund the project. There is currently no organisational body or institutional structure in whose name we can do this, or that can host the project or its future team. 

So we propose to release, in piecemeal form, summary findings of Tim’s account. We propose to do this through this Website (which has carried progress reports of the project, and is the main platform of communication with the community of people who have so far expressed interest in, and support for, the venture). Tim will post installments each month summarising his descriptions of the design, insights into Babbage’s thinking, challenges, difficulties, and analysis. We hope that by sharing exposure to Babbage’s thinking in this way, an appreciation of this remarkable unbuilt machine will spread and reach those motivated to participate in its physical realisation.

Doron Swade

Friday, February 18, 2022

January 2022 report to the Computer Conservation Society

Last November I reported on the successful completion of the first draft technical description, by Tim Robinson, of the Analytical Engine designs. Since then we have initiatives underway to increase the size of the team to take this work further. We have a separate initiative to view working papers donated by Anne Bromley, Allan Bromley’s widow. Allan Bromley, Australian computer scientist, died in 2002. His work was the first attempt to study of the detail of the Analytical Engine designs. Our study of the new Bromley papers will enable us to assess of the scope and depth of his researches and to key Tim Robinson’s findings into what was known before.

Doron Swade

Monday, December 6, 2021

Winter 2021 report to the Computer Conservation Society

Project Report to Computer Conservation Society Committee for Meeting Thursday 18 November 2021

The project has reached a long-awaited defining point. Tim Robinson has completed the first draft of the most comprehensive description yet of the Analytical Engine designs. We have for the first time both an aerial view that integrates partial and seemingly unrelated developments, as well as the most detailed analysis yet of the specifics of implementation.

This analysis has been a prerequisite for the build. Babbage left no design for a complete Engine and the rationale for the ad hoc improvements made over thirty-eight years has not, till now, been fully investigated nor understood. We have lacked the necessary understanding to inform a meaningful build i.e. which signature features of which design should be combined to create a single representative machine.

The treatise, which is a product of five years research founded on a comprehensive review of the entire technical archive, describes six phases of development from 1832 through till Babbage’s death in 1871. At user level, Tim describes and analyses the use of punched cards, the designs for the ‘Great Operations’ (multiplication, division, square root), and for the ‘Small Operations’ (including addition, subtraction, and stepping). The description and running analysis run to some 120,000 words and includes close studies of selected mechanisms. 

Our immediate next step is to structure and edit the material into a form usable by others. This is both to ensure the preservation of the knowledge the document represents, and to provide a working datum for the next stage. We are seeking to appoint someone on a funded basis to collaborate with Tim to produce a document to publishable standards.

In parallel with this we are set to examine the working papers of the late Prof. Allan Bromley. Anne Bromley, Allan’s widow, has donated three large binders of material to the Science Museum and we have made arrangements to access this material at the Science Museum Library in the Dana Centre in South Kensington. The Science Museum has kindly permitted us to copy the material for research purposes. 

Bromley’s publications on the Analytical Engine are masterful, invaluable but regrettably sparse and the extent of his very considerable understanding of the designs is certainly underrepresented in his published output. The examination of these papers will, it is hoped, corroborate our new understanding as well as reveal just how far he had succeeded in decoding Babbage’s intentions.

Doron Swade



Sunday, September 19, 2021

Autumn 2021 report to the Computer Conservation Society

Submitted by Doron Swade to the Computer Conservation Society.

Winding back to last Spring, with the survey of the Babbage manuscript archive complete, we were faced with the choice of pressing on to define what might be built using our current knowledge, or stepping back to evaluate and analyse what was captured in the review of the archive. We decided to step back and Tim Robinson has made substantial progress extending and integrating our understanding of the AE design and its trajectory from 1834 till Babbage’s death in 1871. Tim has identified and describes six phases in the evolution of the AE designs.

These are framed in an overview of the developmental timeline of the whole AE enterprise. There are also focussed pieces on central topics including the use of punched cards, the user view, methods of carriage of tens, and arithmetical process. This work represents the first comparative overview of each of the major designs ('Plans') and provides a new depth of understanding of the overall AE designs and of the developmental arc. The new findings vindicate the decision to take time out to process the material from the archive survey: the work will inform what can meaningful be built given that none of Babbage’s original designs describe a complete engine; secondly, the scholarly value of capturing and documenting a major advance in understanding since Bruce Collier’s work in the 1960s and Allan Bromley’s work in the 1970s and 80s. The immediate next step is to complete this analysis. The project will then move on to defining what version of the AE should be built.

Doron Swade

Thursday, March 25, 2021

Spring 2021 report to the Computer Conservation Society

Submitted by Doron Swade to the Computer Conservation Society.

Tim Robinson has started writing up findings following the review of the complete Babbage manuscript archive. The initial work is in the form of an overview centred on each of the ‘Plans’ i.e. the large ‘systems drawings’ that Babbage shed during the evolution of the designs. The intention was to put to one side further detailed work, for the moment at least, to take stock and to document broad-stroke findings and new insights. Excavating further the hardly-known Plan 30 (there is a Plan 28a but seemingly no Plan 29) proved irresistible both for inherent interest and for completeness. Babbage restarted work on the AE designs in June 1857 after a break of almost a decade and referred to the machine as ‘Analytical Engine 30’. Tim reports that the hardware changes introduced for Plan 30 are ‘dramatic’. One remarkable feature is the extension of the Store to 1000 registers, and most intriguingly various methods of mechanically addressing the store contents. The broad-stroke writing has been paused temporarily while this rich seam is explored. It is not expected to take long and we look forward do the resumption of the interpretative account.

Doron Swade