I was cleaning up my lab and I came accross some quipment I've never seen before. The top looks like a thistle tube, but there is a closed bulb on the bottom. Furthermore, there is another glass piece inside of the stem. The piece inside of the stem is sealed on the top. It has an open at the bottom of the stem near the top of the bulb. I have two guesses.... Some sort of wierd hydrometer that is filled with a liquid to measure relavite density of two liquids. If the small sealed portion inside heates up, the air will expand and bubble out of the tube. If it then cools down, it will suck up the liquid in the larger tube. This would sort of mechanically record the hotest tempearature that the bulb obtained. Another thought just occurred to me. Perhaps this is a cartesian diver. However, I don't think it could be completely submerged. The trapped volume of gas wouldn't overcome the weight of the glass.