For demonstrating the phenomenon of thermal convection in liquids caused by temperature variation. Consists of a rectangular-shaped borosilicate glass tube 18 MM with a funnel-shaped opening at the top for filling liquids. When tube is partially filled with water and heated at one corner after adding a dye, potassium permanganate crystals, sawdust, or aluminum powder, the movement of colors or particles illustrates the formation of convection currents.