English: A description of the procedure used is found on page 67, of Tainter's unpublished autobiography. There, Tainter quotes Chichester Bell as follows: "A jet of bichromate of potash solution, vibrated by the voice, was directed against a glass plate immediately in front of a slit, on which light was concentrated by means of a lens. The jet was so arranged that the light on its way to the slit had to pass through the nappe and as the thickness of this was constantly changing, the illumination of the slit was also varied. By means of a lens ... an image of this slit was thrown upon a rotating gelatine-bromide plate, on which accordingly a record of the voice vibrations was obtained."