Ferdinand-Philippe Carré invented this type of electrical machine, combining friction and induction, in 1868. The two disks are rotated by means of a pulley system. The lower glass disk is rubbed by two leather cushions, while the surface of the upper ebonite disk receives induced charges from a brass comb opposite the glass disk and carries them continuously to the other collecting comb secured to a large brass prime conductor at the top of the instrument. The lower comb can be brought into contact with the conductor by means of a long brass electrode with ebonite handle, thereby varying the spark length to a maximum of c. 150 mm. A large ring at the lower side of the conductor is for attaching Leyden jars. The Carré machine was mostly distributed in France and used in electrotherapy. This specimen was made by Adolphe Gaiffe.