We all know the old joke. There are 10 types of people. Those who understand binary and those who don't. Well I think I might have stumbled upon something that might help those folks who don't understand or at least have a problem visualising it. It's not quite Charles Babbage's Difference Engine, but some eccentric Canadian dude has built a 6 bit binary adding machine out of wood using marbles as the bits. It is really rather smart in that it actually isn't a million miles away from how a digital computer does it - obviously without the marbles! - but it is also a lovely bit of woodwork.
If you like this then you can visit the dudes Web Site where he explains exactly how he did it.