This classic thermometer was designed by Galileo, and works off the principle that the density of a liquid changes as the temperature changes. This thermometer is accurate to singular degrees, and was made popular by sailors in the golden age of discovery, as it was one of the most accurate ways to find the temperature out at sea. Accurate temperature reading hand blown glass 71cm inches tall gold plated tags measures temperatures 16 to 40 degrees. instructions included Designed for ages 12+ (Not a toy. Keep away from young children) There’s no more beautiful way to measure the temperature than using a Galileo thermometer. This fairly accurate instrument is based on the thermoscope invented by Galileo Galilei in the early 17th century. Unlike your typical mercury-in-glass thermometer that’s basically a narrow bulb made with mercury that expands and contracts, the Galileo thermometer is far more complex. It’s comprised of multiple glass spheres each filled with a colored liquid mixture which often contains alcohol but can even be simply water with food coloring added. These floating balls sink or float inside the surrounding water over time and temperature ever so slowly and gracefully.