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