MAURO FERMARIELLO / SCIENCE PHOTO LIBRARY MAURO FERMARIELLO / SCIENCE PHOTO LIBRARY
Early electromagnetic seismometer invented in 1856 by Luigi Palmieri. The device has mercury-filled tubes arranged along the points of the compass. During an earthquake, the movement of the mercury closed an electrical circuit. This stopped a clock and started a paper tape (upper right to bottom centre), which was marked with a pencil upon further movement of the mercury. The movement of a spring-mounted weight was also measured. Hence the time, duration, and intensity of an event were recorded. However, a true seismograph also records the waveform of the shock. Photographed in the museum at the Vesuvius Observatory, Naples, Italy, which Palmieri directed.
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