Heroes of the Telegraph

The property on which the receiver was based had been observed and applied by him some time before. When a current is passed from a metal contact through certain chemical salts, a lubricating effect was noticeable. Thus if a metal stylus were rubbed or drawn over a prepared surface, the point of the stylus was found to slip or 'skid' every time a current passed between them, as though it had been oiled. If your pen were the stylus, and the paper on which you write the surface, each wave of electricity passing from the nib to the paper would make the pen start, and jerk your fingers with it. He applied the property to the recording of telegraph signals without the help of an electro-magnet, by causing the currents to alter the friction between the two rubbing surfaces, and so actuate a marker, which registered the message as in the Morse system.