Subject: How can I make a mercury tilt switch without using mercury

I'm an artist, and i'm trying to build a system to detect the vibrations of 
passing trucks. I've used a mercury tilt switch before. But want to make a 
better system. I have some large glass tubes. I've filled these with water, 
to see if they would work, but they produce too much condensation. The 
'ripples' created by the vibrations are too small and the size of the 
miniscus too great to be of much use.

Mercury sounds too dangerous, do you have any other suggestions?

many thanks

Re: How can I make a mercury tilt switch without using mercury