(If you are unfamiliar with this type of thermometer, I will describe it in some detail in a PS, below.) Clearly, the Galilean thermometer cannot be either "dual labeled" or "switchable" for reading in either Celsius or Fahrenheit. I'm not even sure if I would call it an analog or a digital device; perhaps it would be classified as a hybrid.
While in Europe on a recent trip, I found Galilean thermometers in gift shops in several towns along the Danube, from Nurnberg to Vienna. No doubt they are available elsewhere but they happened to be more abundant in this area which is noted for it's decorative glass pieces (of which the Galilean thermometer is certainly one).
Much to my annoyance, I discovered that ALL the Galilean thermometers in the shops were constructed to show Fahrenheit temperature! Clearly, the shops were in business primarily to sell souvenirs to American tourists.
But I figured, "This is Europe! Surely they must have some of these things in Celsius for the European visitors." So I asked and, with just a little disruption (because the shop was very busy), someone was sent down the street to the shop where these things were made and stored and a Celsius version was brought to me. I was delighted and bought it. It now sits prominently in my living room.
Regards, Bill Hooper
PS Description of Galilean thermometers.
The Galilean thermometer consists of a vertical tube filled with a clear fluid (water?). In this fluid are several small glass globes. The globes contain air and a small amount of fluid (water?) which is colored. The fluid is a different color is in each little globe, which adds to the thermometer's beauty as well as its utility.
The air-water combination in each globe is adjusted so that the globes just barely float (have neutral buoyancy) in the fluid of the main tube. But the density of the fluid of the main tube is temperature dependent (like all fluids, of course). That means that, if the globes are exactly neutral buoyancy at some specific temperature, then they will float up to the top if the actual temperature is a little cooler and settle down to the bottom if the temperature is a little warmer.
In the Galilean thermometer, each of the several little globes is adjusted to float at a different temperature; and each globe is labeled with that temperature. In use, one merely needs to notice which is the lowest of the floating globes to determine the surrounding temperature (assuming the thermometer is in equilibrium with its surroundings).
My Galilean thermometer registers the temperature in the range from 18 �C to 26 �C in steps of 2 �C. That's not a wide range and it is not very precise. Clearly it is more a work of art than a scientific instrument.
