Thermometer of some type. I think it's called a Galileo thermometer. I have one sitting at home. They were all the rage a few years ago

Yes correct Gabba.

It's called Galileo's Thermometer and named after Galileo Galilei, the man pretty much responsible for the birth of modern science. How does it work?  The thermometer is a sealed glass cylinder containing clear liquid and a series of objects that rise and fall depending on mathematical principle. Basically, they rise and fall as the temperature changes.

The mathematical principles applied to the Galileo thermometer are straightforward. Each bulb in the thermometer has the same volume and therefore exactly the same density. This means that each bulb has the same magnitude of both gravitational and buoyant forces. Gravity pushes down, buoyancy upwards.

They are all listed here in a sub topic under lounge

http://www.localweather.net.nz/smf/what-is-it/97/

Cheers