One will find that as ambient temperature rises the spheres descend one by one. The ones above ambient temperature remain floating at the top of the fluid.

One reads the actual temperature ‘in a Galileo Thermometer‘ by checking a numbered medallion that hangs each small globe within the fluid. The number on the tag of the lowest sphere that is still floating will provide one an accurate temperature measurement.

The Galileo thermometer comes with colored glass spheres weighted precisely to respond to changes in temperature by rising or falling in a glass cylinder filled with liquid.

Each sphere in the cylinder has a little tag with numbers attached. Read the numbers on the sphere that floats the lowest in the cylinder, and that indicates current air temperature. Each Galileo thermometer sphere is dual calibrated for accuracy.