A nerdy little shot, but here goes.... These little glass bubbles float inside of a sealed glass tube, filled with paraffin oil. The little spheres rise and lower with fluctuations in temperature and corresponding density. As the temperature of the air outside the thermometer changes, so does the temperature of the fluid surrounding the bubbles. As the temperature of the fluid changes, it either expands or contracts, thereby changing its density. So, at any given density, some of the bubbles will float and others will sink. The bubble that sinks the most, indicates the approximate current temperature. These glass bubble were not at the bottom, but they were pretty.
Another busy "inside" day, so this will have to do. On a personal note, my dearly loved departed father-in-law bequeathed this item to us. He was a true scholar and gentleman, with an endlessly curious mind and gentle manner.
10/1/2020: Finished year 7 (!), with continuing gratitude towards this amazing community. Based in St. Louis, MO. Regular worker-bee and self-taught photography dilettante....
I've got one of those too, and love watching the little bubbles do their thing. Don't let anyone knock it over though. I gave my daughter a Galileo thermometer a while back and one of her daughters broke it. Apparently the liquid is difficult to clean up.
