With the beautiful floating glass spheres indicating room temperature.
This German handcrafted thermometer uniquely demonstrates the scientific principle established by Galileo in the 17th century that a liquid's density changes with the temperature.
The colorful glass spheres, with their temperature tags, rise one by one as the liquid temperature rises and descend as temperature falls. The lowest sphere among those at the top indicates the temperature. Read this Wikipedia article for more detailed information about how the Galileo thermometer works. (Link opens new window.)
This 13" Fahrenheit Galileo thermometer has five spheres for temperatures 80°, 76°, 72°, 68°, 64°.