Halloween. I went as the Spirit of the Night though Patrick thought I was Ash Man. It came off, fortunately.
Sunday was wet, so over the new bridge to the Museum of Technology which is a rather odd place, housed in the former sewage pumping works and city rubbish burner, now housing a miscellaneous collection of engines pumps and random electical items from Cambrdige's industrial heritage; and run by a collection of enthusiasts. Its great failing (compared, say, with the FitzWilliam) is that it doesn't have a decent cafe, or indeed a cafe at all really (though they will sell you a coffee at the ticket kiosk)).
They were hosting a Teslathon which was an occaision for an even odder bunch of enthusiasts to gather and mostly show each other their endeavours, though incidentally the public too. I later find some stuff on wiki about this, and find I'd guessed some of it right - the spark-gaps are to generate AC but the hair-dryer isn't there to cool it down, it affects the frequency. On guy had managed the trick of getting them to play music, and had a version that would rotate round as the sparks exited. The bigger machines were very very noisy - the spark gap I think. Sadly they didn't have much in the way of explanation available on site.
Daniel thought that the rock crushing machine was the best. 
Incidentally: from the Rubaiyat:
Ah, fill the Cup:---what boots it to repeat
How Time is slipping underneath our Feet:
Unborn TO-MORROW, and dead YESTERDAY,
Why fret about them if TO-DAY be sweet!
- why does this make sense? Why not "unborn yesterday and dead tomorrow"? Someone explain it to me. [Update: Sidd has done so; my thanks. Unborn/Dead refer to the days, not to the people. La! -W]
[Update: http://picasaweb.google.com/thouky/CambridgeTeslathon2009?authkey=Gv1sR… too -W]
Today is sunday. saturday is dead. monday is not yet born.
the author was unborn yesterday, and dead tomorrow, but he is not speaking of himself.