Glass Thermometer!

Amazingly it is possible to tell the room temperature from this object bought some years ago in a little shop selling unusual objects!
Each of the little glass balls floating in the liquid has a little metal disc hanging below it with a Centigrade temperature printed on it. We have no idea what the liquid is but some of the balls move up and some move down. The room temperature is said to be that on the bottom bead at the top of the tube! Have you any idea how it works ……!!