Measuring gravity to the sixth decimal place was one of the nineteenth century’s quiet obsessions, and this Smithsonian study tells the instrument’s story: Kater’s convertible pendulum, the great geodetic surveys, and the invariable pendulums carried up mountains and across oceans to map the Earth’s changing pull.
It is precision measurement as history — small brass instruments in the service of planetary questions. Download the free EPUB for the pendulum’s imperial century.