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
