Spring 2016 report to the Computer Conservation Society

This was presented on May 11 to the Computer Conservation Society by Doron Swade.


We have been pecking away at Babbage’s original design drawings for some while now and have found with regret that we are unable to reverse engineer a coherent and consistent understanding of the Analytical Engine from the mechanical drawings alone. There are some 300 drawings and some 2200 Notations – descriptions of the mechanisms using Babbage’s language of signs and symbols. There were three phases of design - early, middle, and late.There is overlap between these, there are ad hoc upgrades, and only fragmentary explanation, where there is explanation at all.

It remains unclear whether any of these three phases is graced by a complete design. This in itself would be unfortunate but not catastrophic as mechanisms can be devised as functional replicas for omissions provided the intended function is fully understood. The immediate problem is that the extent of incompleteness is not clear. The work of the late Allan Bromley in decoding the AE designs in invaluable but he published only a small part of his substantial findings and these are anyway based on only part of the archive. While much is understood about many of the main mechanisms and the general scheme, there remain fundamental aspects control and sequencing that are not yet well understood and have resisted further illumination.

To achieve a more comprehensive understanding of the designs Tim Robinson in the US is going through the entire Babbage archive (over 7000 manuscript sheets) and producing a cross-referenced searchable data base. The purpose of this is to marshal all known sources so that we have a bounded idea of all relevant material. The intention is to reveal any explanations and/or drawings that Babbage might have left that have not yet come to light.

A second line of attack is to the 2200 Notations for the AE using the newly acquired knowledge of the Mechanical Notation. Allan Bromley maintained that the Notations were indispensible to his understanding. However he did not publish how he had used the Notations and he was the last to use them as an interpretative tool. The hope here is that the Notations will provide some of the missing information about logical control and moreover give insights into design strategy. In parallel with Tim’s comprehensive data base index I am going through the twenty volumes of Babbage’s ‘Scribbling Books’ identifying all material on the Mechanical Notation – a fast-track way of accessing this specific material.

Currently the stages envisaged for the project are:

1. Finalising research of the original design
2. Specifying a viable version
3. Computer modelling and simulation/3D printing
4. Manufacture and construction

We need more hands to the pumps and have latterly diverted some effort to fundraising. We have a 3-year plan at the end of which we expect have the requisite understanding of the designs, a platform from which to specify a viable version of an AE that is historically authentic, and to have trialled tools for modelling and simulation. The funding proposal includes pulling in requisite expertise including modellers and mechanical engineers.

In summary, we have had to bite the bullet with the realisation that without a concerted assault on the sources, a fuller understanding of the Engine design will not be forthcoming. We need to understand the intentions of the design well enough to identify missing mechanisms and understand their intended purpose well enough to devise fill-ins that are consistent with Babbage’s design style. Effort is now divided between continued study of the designs and fundraising to ramp up the effort.

Doron Swade

Winter 2015: Project Report to the Computer Conservation Society

The following report appeared in the Winter 2015 Resurrection:

The bicentennial year of Ada Lovelace’s birth falls this year. Preparation for various celebratory events has directed attention to Ada Lovelace’s ‘program’ (1843) to calculate Bernoulli numbers using Charles Babbage’s unbuilt Analytical Engine. A small group including Tim Robinson in the US, Rainer Glaschick in Germany, Bernard Sufrin in the UK (and me) have been collaborating in exploring the ‘program’. Significant progress has been made with many obscurities now illuminated. The study has directed new attention to how the several types of punched card control the internal microprograms on the one hand, and how these functions interface with the user on the other.

There has been significant archive activity. The major historical source is the Babbage technical archive held by the Science Museum. The Science Museum digitised the archive in 2012 is now preparing to provide open access to the archive. The Analytical Engine project team has been the main user of the digitised archive under special licence. In the course of the project mismatches have been identified between the digitised material and the existing printed index compiled by the late Allan Bromley and published by the Science Museum in 1991. Referencing anomalies, identification of material omitted from digitisation exercise and other structural issues have become evident. Descriptions of these have been compiled and we are working with Science Museum archivists to resolve and correct these ahead of open access release. The work is detailed and, given the volume of material, substantial. Eye-strain is an ongoing hazard.

This archive work has suggested a new and significant prospect for the role of the Notation in an understanding the designs. One of the difficulties in understanding the designs is the need to reverse engineer logical function from mechanical drawings of mechanisms - this without textual explanation of purpose or intention. The original hope was that the notations, expressed in Babbage’s symbolic descriptive language, would contain a higher-level logical description that would relieve this difficulty. As described in earlier reports the main features of the Notation were decoded from a detailed knowledge of the mechanisms of Difference Engine No.2. The provisional conclusion from that study was that the notations are a description of the mutual physical relationships of mechanical parts and are not an abstraction of a logical description of the Engine’s function. Further, that the mechanical design preceded the notational description. New material found in the archive suggests that while this might be true for Difference Engine No.2 the notations for the Analytical Engine (about 2,700 of these) may indeed embody higher-level logic, control functions for sequencing the punched cards and orchestrating the internal operations that the punched cards control. If so, the notations would provide the explanatory tool we have been looking for and the prospect of this is enough to distract one from the plight of refugees migrants and austerity, even if only briefly.


Doron Swade

Further progress as reported to the Computer Conservation Society

Progress continues decoding Babbage’s Mechanical Notation – the language of signs and symbols Babbage devised to describe the mechanisms of his calculating Engines. There has been a new archival find in manuscript papers Babbage gave to a younger colleague, Harry Wilmot Buxton. The Buxton papers are held by the Museum of the History of Science, Oxford. The papers were known about and some material has been published but last time the papers were viewed predates the focussed interest on the Analytical Engine, and the significance of the material on the Mechanical Notation passed unnoticed. With the kind permission of the archivist, permission was given for a copying rostrum to be used and the relevant material was digitally photographed in situ. The significance of the material is two- fold: it contains Babbage’s efforts to provide generalised rules for annotating his mechanical drawings; secondly, the principles it documents confirms our findings from the earlier exercise in which knowledge of the Difference Engine mechanisms were used to decode the Notations that describe them – this without the benefit of generalised rules of syntax orgrammar. The agreement between the archive and our earlier findings is a satisfying vindication of the decoding method using known mechanisms.

The Ada Lovelace bicentennial, celebrated this year, has directed attention to the Analytical Engine through the description of the Engine Lovelace published in 1843. Her description of the Engine is in the form of Notes which form a substantial addendum to the account by Luigi Menabrea who wrote up some of Babbage’s lectures on the Analytical Engine Babbage gave in Turin in 1840. The ongoing preparation of celebratory exhibitions, symposia andmedia coverage, has redirected attention to specific features of Lovelace’s description. One such is the use control arrangements between the punched card input and the routing of information between the cards, processor and memory. It appears that there is no form of indexed or relative addressing either of which would be required for the AE to execute the example given by Lovelace - the calculation of Bernoulli numbers. It is far from clear how the Engine executes its control functions and there are several ongoing collaborative conversations between scholars and historians analysing the issue stimulated by the extended interest in Lovelace’s work. The lesson we have taken is that much as is known about the principles of the AE, there is much that is not understood at the fundamental level of internal control and such understanding is a prerequisite of any construction, physical or virtual.

Doron Swade

Autumn 2015: Progress Report for the Computer Conservation Society

The following appear in the Autumn 2015 Resurrection

There has been a new archival find in manuscript papers Babbage gave to a younger colleague, Harry Wilmot Buxton. The Buxton papers are held by the Museum of the History of Science, Oxford. The papers were known about and some material has been published but last time the papers were viewed predates the focussed interest on the Analytical Engine, and the significance of the material on the Mechanical Notation passed unnoticed. With the kind permission of the archivist, permission was given for a copying rostrum to be used and the relevant material was digitally photographed in situ. The significance of the material is twofold: it contains Babbage’s efforts to provide generalised rules for annotating his mechanical drawings; secondly, the principles it documents confirm our findings from the earlier exercise in which knowledge of the Difference Engine mechanisms were used to decode the Notations that describe them — this without the benefit of an generalised rules of syntax or grammar. The agreement between the archive and our earlier findings is a satisfying vindication of the decoding method using known mechanisms.

The Ada Lovelace bicentennial, celebrated this year, has directed attention to the Analytical Engine through the description of the Engine which Lovelace published in 1843. Her description of the Engine is in the form of Notes which form a substantial addendum to the account by Luigi Menabrea who wrote up some of Babbage’s lectures on the Analytical Engine Babbage gave in Turin in 1840. The ongoing preparation of celebratory exhibitions, symposia and media coverage, has redirected attention to specific features of Lovelace’s description. One such is the use control arrangements between the punched card input and the routing of information between the cards, processor and memory. There is evidently no form of indexed or relative addressing either of which would be required for the AE to execute the example given by Lovelace - the automatic calculation of Bernoulli numbers. It is far from clear how the Engine executes its control functions and there are several ongoing collaborative conversations between scholars and historians analysing the issue stimulated by the extended interest in Lovelace’s work. The lesson we have taken is that much as is known about the principles of the AE, there is much that is not understood at the fundamental level of internal control and such understanding is a prerequisite of any construction, physical or virtual.


Doron Swade