3 Aurora flasks

These closely similar aurora flasks were used, as the name suggests, to study the phenomenon of the northern lights, the aurora borealis. In the 17th century, Jean Picard discovered that an electric discharge in an evacuated tube causes a glow of light. This glow looked very much like the Northern Lights, that is why many scientists looked to electricity for an explanation of this phenomenon. The first director of Teylers Museum, Martinus van Marum, investigated these light phenomena too, and he became convinced that the Northern Lights were caused by an electric discharge in vacuum. The lower half of the flasks is covered in tin foil, which can be earthed by taking the flask in your hand. From the knob at the top, an electrode (a rod) descends into the middle of the flask. As soon as the knob is connected to an electrostatic generator, bands of light appear between the electrode and the glass wall.