Friday, March 22, 2019

March 2019 report to the Computer Conservation Society

This was presented on March 21, 2019 to the Computer Conservation Society by Doron Swade.

The sheet-by sheet inspection of Babbage’s vast technical archive is now in the end game after some three years.  The last progress update reported that Tim Robinson, in the US, working from the digitised images of the manuscripts, was close to completing a review of the known catalogued material in the Science Museum archive and that one of the final tasks was a scrape of a relatively small but potentially critical set of drawings that had not been catalogued or scanned the contents of which are largely unknown.  Tim is currently in London spending a week going through this material.  This material evaded the Science Museum’s scanning operation in 2011 largely because it was not listed in the catalogue prepared by the late Allan Bromley who compiled the first near-comprehensive record, published in 1991, of the Babbage technical archive.

There have already been significant finds.  The Notations for Difference Engine 1, dating from 1834, thought to exist, had never come to light.  These have now been found and represent a crucial piece in the puzzle of the developmental trajectory of the symbolic language Babbage developed as a design aid, to describe and specify his engine, and used extensively in the development of the Analytical Engine.

Equally significant is the discovery of what is thought to be the legendary Plan 28a, part of the most advanced design for the Analytical Engine.  There have been references to Plan 28 and Plan 28a designs peppered through the late manuscripts and some design drawings, but the existence of this plan has never been confirmed.  Bromley told me in the late 1990s that he questioned whether it had existed as a separate entity in the first place in which event ‘Plan 28’ may have been a federation of improvements added to previous designs.

The survey so far has identified mis-titled drawings, single drawings that have two unrelated catalogue entries, and drawings known to exist from earlier scholarly work but not located.  These findings are openly shared with the Science Museum archivists in what has become a model collaboration between content specialists and archivists. We await the completion of this week’s inspection in the hope and expectation of more surprises.

Doron Swade


  1. Wonderful! I would /love/ to see a preview / teaser of the Plan 28a document to share on social media if you feel like stirring up more support.

  2. This sounds very exciting! I can't wait for something to be shared with the public.

  3. I've posted about this on Slashdot, which may drive some traffic and interest. I've done the same in the past, but don't know if it does any significant good. The story is at