Ambient Weather WS-GA1141305 13" Galileo Thermometer with 5 Glass Balls and Gold Tags The Galileo thermometer consists of a sealed glass tube that is filled with liquid and several floating bubbles. The bubbles are glass spheres filled The Galileo thermometer consists of a sealed glass tube that is filled with liquid and floating bubbles Attached to each bubble is a little metal tag that indicates a temperature. These metal tags are calibrated counterweights. The weight of each tag is slightly different from the others The bubbles are calibrated by adding a certain amount of fluid to them so that they have the exact same density. So, after the weighted tags are attached to the bubbles, each differs very slightly in density As the temperature of the air outside the thermometer changes, so does the temperature of the liquid surrounding the bubbles. As the temperature of the liquid changes, it either expands or contracts Includes one year factory warranty from Ambient Weather The Galileo thermometer consists of a sealed glass tube that is filled with liquid and several floating bubbles. The bubbles are glass spheres filled The Galileo thermometer consists of a sealed glass tube that is filled with liquid and floating bubbles. Attached to each bubble is a little metal tag that indicates a temperature. These metal tags are calibrated counterweights. The weight of each tag is slightly different from the others. The bubbles are calibrated by adding a certain amount of fluid to them so that they have the exact same density. So, after the weighted tags are attached to the bubbles, each differs very slightly in density. As the temperature of the air outside the thermometer changes, so does the temperature of the liquid surrounding the bubbles. As the temperature of the liquid changes, it either expands or contracts. Includes one year factory warranty from Ambient Weather.