00:00Suspended bronze vessels resonated with subterranean vibrations to detect enemy soppers.
00:06Ancient military writers like Vigetius described placing bronze vessels in tunnels to detect subterranean excavation sounds.
00:14As subterranean pickaxes struck Earth, the seismic shockwaves coupled into the air and vibrated the resonant bronze.
00:22Guards watched for tiny ripples on water surfaces or vibrating indicators to detect enemy vibrations.
00:28Suspended bronze vessels acted as acoustic resonators, detecting the vibrations of enemy sappers.
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