Check the temperature at a glance with this classic analog Stainless Steel Thermometer. Hang this thermometer indoors or out and read the temperature in degrees Fahrenheit from -20° up to 110°. This thermometer uses a mercury-free liquid to indicate the temperature, and the housing is fully weatherproof. Based on principles first put into practice by Hero of Alexandria in the first century AD, analog thermometers measure the temperature based on the expansion or contraction of the liquid in the tube caused by rising or falling temperatures. The Fahrenheit scale used on this example was developed in 1724 by Daniel Gabriel Fahrenheit with the 0° measurement being set by the temperature of a solution of brine made of equal parts salt and ice. Size: 2¾"W x 9"H x ¼"D.