Galilean Thermometer: a hot day in Cumbria

This doesn't usually happen. In hot weather, the clear liquid in the thermometer expands and becomes less dense. The balls in the middle float when they are less dense than the clear liquid. The balls have different densities that are linked to the density of the clear liquid at a given temperature. The lowest ball is the most dense of the 4 balls and sinks when the temperature reaches 20 degrees Celsius.