MAURO FERMARIELLO / SCIENCE PHOTO LIBRARY MAURO FERMARIELLO / SCIENCE PHOTO LIBRARY
Early portable seismometer invented in 1876 by Luigi Palmieri. It was based on his earlier electromagnetic seismometer, which used mercury- filled tubes. 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. True seismographs also record the waveform of the shock. Photographed in the museum at the Vesuvius Observatory, Naples, Italy, which Palmieri directed.
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