Exhibitions: A Trove Come True

There used to be lots of gold in them thar hulls. Over the centuries, Spain exacted an estimated $8 billion in tribute from its New World colonies, and probably $1 billion of that was hijacked by pirates on the high seas or sank beneath the waves during storms. These lost riches still haunt the imagination, and to addicts no space-age adventure is as exciting as the search for sunken treasure. Exciting and occasionally profitable. An engrossing sampling of one briny trove, the salvage of an armada wrecked in the 18th century off Florida, was put up for auction last...