Smithsonian Galileo Thermometer Rising to the Occasion Despite its scientific shape, it is easy to read this mouthblown glass iteration of the Galileo Thermometer The varying density of the glass spheres within the cylinder of this Galileo Thermometer allows them to rise or fall as temperatures change Simply identify the lowest floating sphere and its tag will indicate the temperature with an accuracy within 2&deg;, between 68&deg; to 80&deg; Fahrenheit. 15"h. x 3.125"dia.