Hold the lower bulb in the palm of your hand and wrap your fingers around it. The heat of your hand increases the temperature of the gas in the lower bulb. The increase in temperature creates an increase in air pressure; the gas is dilate. This increased pressure pushes the lamp fluid from the bottom to the top of the tube, in the top bulb. When all the liquid was transferred from the bottom bulb, air bubbles are pushed into the tube from the bottom, which gives the impression that the top fluid is boiling.

 

Height 18 cm

Width 4 cm

 

Verre