Full technical description of Charles Babbage's Difference Engine No. 2

From: Doron Swade via Members [email protected]
Date: December 2, 2023 at 10:00:21 AM EST
To: [email protected]
Cc: Doron Swade [email protected]
Subject: [SIGCIS-Members] Babbage Engine - Full Technical Description on Open Access
Reply-To: [email protected]

Dear All

I am pleased to report that the full technical description of Charles Babbage’s Difference Engine No. 2 has recently been made available online on open access by the Science Museum (London).

The Engine was built to Babbage’s original drawings (1847-1849) and completed in 2002. It has 8,000 parts, weighs 5 tonnes, and works as Babbage intended. It is the first of Babbage’s calculating engines to be built in its entirety.

Over the decades-long life of the project I documented the interpretation of the 19th-century drawings, the design decisions made in its construction, its assembly, operational debugging, and what was learned from running the Engine for countless live public demonstrations.

A full description of the Engine is presented in two works available online:

Difference Engine No.2 Technical Description (232 pages, 131 illustrations)

Provides a detailed interpretation of Babbage’s design, and documents the technical understanding that informed the successful construction of the working machine.

Difference Engine No.2 User Manual (147 pages, 199 illustrations)

Documents the practical procedures for operating the Engine safely, setting up a calculation, testing, trouble-shooting, fault-finding, and maintenance including lubrication.

The two documents are free-standing i.e. relevant drawing-excerpts are embedded in the text so that understanding does not, for the most part, rely on reference to the full 19th-century design drawings.

Direct Browser Links:

Technical Description:


User Manual:


Additional Material

The Babbage Papers at the Science Museum:

  • Digitised archive of Babbage papers including full technical archive and Notebooks.


Charles Babbage’s Difference Engines and the Science Museum | Science Museum

  • Short contextual and historical summary.
  • Links to the Technical Description and User Manual are in Further Reading.

Charles Babbage’s Difference Engines and the Science Museum | Science Museum


Swade, Doron, Charles Babbage’s Difference Engine No. 2: Technical Description . Science Museum, 2023.

Swade Doron, Charles Babbage’s Difference Engine No. 2: User Manual. Science Museum, 2023.

Best wishes

Doron Swade

1 Like

that people have built these things purely to see how they work is astounding.

Something that was at best an educated theory in its day with the lack of funding keeping it from happening… being a hobby project.