These
Galileo solid glass thermometers contain hand-blown multi-colored glass spheres featuring GOLD PLATED MEDALLIONS. This functional and attractive desk accessory is based on the physicist Galileo Galilei’s (1564-1642) discovery that the density of fluid expands and contracts depending on temperature. The lowest floating sphere in the upper group indicates the current temperature. As the temperature decreases, spheres will rise and as the temperature increases, spheres will fall.
Please note that the Galileo thermometer is a scientific instrument and not a toy.