Ambient Weather WS-YG709 Galileo Thermometer, Barometer, Hygrometer and Quartz Clock Weather Station (Silver) The rich, wood framed classic weather station measures temperature (Galileo), barometric pressure (in and mbar), humidity (%) with analog clock 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 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, thereby changing its density So, at any given density, some of the bubbles will float and others will sink. The bubble that sinks the most indicates the approximate current temperature The rich, solid wood framed cherry weather station with lacquer finish measures barometric pressure (in mbar and inHg) and humidity (%). The barometer allows for sea-level calibration up to 3,000 feet