Happy Babbage’s Birthday Everybody!

Happy (ever so slightly belated in the UK as I post this) Babbage’s Birthday everyone! I know everyone’s favourite part of the annual celebrations is the Numbers Banquet and the Parade of Algorithms, but for the TRUE MEANING of Babbage’s Birthday you ought to rejoice in the Mechanism Sermon, herein…


Sorry about the rambling, total lack of pedagogic structure, and my irritating squeaky voice! I did this for a thing but recalled I promised to explain how this thing worked like, a year ago.. anyways now you know what the lovely rippling arms on the back of the Engine do:

By the way the ‘chack!’ sound that it makes is the locks that click down to stop the wheels, that’s the long grey wedge thing on screen right.



  1. Quinn on January 4, 2015 at 11:21 pm

    ooooh the anticipating carriage sounds interesting just from the name! I’m imagining some kind of base 10 widgety version of Carry Lookahead logic going on :3

    • Danny on January 6, 2015 at 10:12 pm

      Actually, Quinn, at it’s “BASE” it’s really a quite “BINARY” mechanism… a carry will occur soon or it won’t…. ( binary… base 2.. get it? hee hee.. ) It’s really nicely described in one of the Allan Bromley articles in the IEEE Annals in the History of Computing journal… sometime around 2000 or 2001, I think…

      Bye.. :0)

  2. palenoue on January 3, 2015 at 6:21 pm

    Where do you add the cats?

  3. Ken on January 2, 2015 at 1:37 pm

    Not a bit squeaky. Happy New Year.

  4. Jeff Lee on December 29, 2014 at 5:18 pm

    I’m guessing that’s Difference Engine No. 2? (In the photos I’ve seen of the “Beautiful Fragment”, the number wheels have only one set of numbers around their circumference, but in those videos, they each have four sets. (And, obviously, things are far more compact vertically in these videos than on the Fragment.)

    Apart from the compactness, how much difference was there in the mechanisms between No. 1 and No. 2?

    • Joe Green on January 1, 2015 at 4:41 am

      Jeff, that link teaches me how to use the telephone. Oops. Serendipitously educational, though, as it spells goodbye “goodby”. I never knew that was (or should I say had been) the US spelling.

    • sydney on January 1, 2015 at 7:04 pm

      Hi Jeff– yep, that’s the number 2 design– the four repetitions of the digits is so that the wheels would have less rotation to increment a number. It’s a completely different design from No. 1 in fact, and the Analytical Engine adder is completely different again.

    • Danny on January 5, 2015 at 12:59 am

      Hiya.. according to this citation, http://ed-thelen.org/bab/DoronSwadeIEEE.pdf , DE-1 would have used about 25,000 parts, while DE-2 used about 8,000 for similar calculating capacity….


  5. palenoue on December 27, 2014 at 6:02 pm

    Any chance you could make that model into files that can be printed on 3D printers? I’d love to make a working model of that “simple” mechanism to show people how the difference engine worked.

    • sydney on December 28, 2014 at 11:21 pm

      I’m actually planning on doing exactly that! Stay tuned..

      • palenoue on January 3, 2015 at 6:20 pm


  6. MadRat on December 27, 2014 at 8:55 am

    That second video was so shaky I had to close my eyes lots of times just to keep from getting sick. Not your fault, I know.

  7. Roberto Keller on December 27, 2014 at 3:37 am

    Got it! Thanks for the explanation!

  8. John on December 27, 2014 at 2:25 am

    Is the giant hand available to serve drinks at other parties, or just Babbage Day?

    Not to contradict Babbage, here, but electronics courses still teach ripple-carry adders, which is the equivalent to this model, even though the carry-lookahead adder (the digital version of the anticipating carriage) has been around since the ’50s.

    Happy new holidays!

  9. Brian on December 27, 2014 at 1:35 am

    Ahhh, I can’t WAIT for the book to be published.

  10. Rico on December 27, 2014 at 1:06 am

    OMG. I didn’t realize Babbage was so small. Or maybe you’re just that huge? Nah, I’m going with tiny Babbage. Either way, fabulous.