This glass tube was used to produce electrical glow in partial vacuum. The English physicist William Henley used a similar instrument to show the luminescence produced by positive and negative discharges—a phenomenon that he saw as proving Benjamin Franklin's theory of a single electrical fluid. In 1780, Filippo Lucci depicted a comparable device in the Stanzino delle Matematiche in the Uffizi, a clear indication of the interest aroused by such demonstrations in the late eighteenth century.

The tube is supported on a glass pillar with a turned mahogany base, weighted by means of a lead ring to prevent the instrument from toppling over. A brass spike projects at right angles from the upper brass collar, and a ball electrode is joined to the lower collar. Inside the tube are two other electrodes: a pointed electrode at the top and a ball electrode at the bottom.

An air pump is used to produce a partial vacuum inside the instrument. The glass is rubbed with a cloth, or the electrodes are touched with the conductor of an electrostatic machine. The electrification illuminates the inside of the tube, generating a glow very similar to an aurora.