This thermometer is based on a scientific principal discovered by Galileo. As the liquids in the cylinder contract slightly at higher temperatures, the spheres of slightly different weights rise; as the liquids cool, the spheres drop. The lowest floating sphere in the upper part of the cylinder tells the correct temperature, from 66 to 84 degrees, in 4-degree increments. Made of glass, its an attractive and fascinating way to measure the temperature of your home. 17"h, 3 1/4" dia.