Millikan's apparatus, permits the atomising of a latex solution into small spheres and the rubber hose induces a static charge upon them. They are introduced between charged plates in the form of a cell. As the voltage between these cell plates is reversed, the particles are attracted to one plate or the other. Their movement is viewed through a small telescope with a graticule. Power sources are required to be connected. Knowing the potential on the cell plates and plotting the velocities of the spheres permits the calculation of the charge on a single electron.