TO UNDERSTAND WHAT was a risky venture in 19th-century America, visit the Whaling Museum in Nantucket. The industry thrived on this Massachusetts island, now transformed from an outpost for coarse sailors into a swanky beach spot. Two centuries ago, whales were valuable because of the lucrative oil in their head-cases. Captains amassed fleets of sloops and dozens of men armed with harpoons to hunt them. For lucky crews that found their “white whales” the rewards were enormous, but so were the risks of losing ships and souls in the hunt. In “Moby Dick” Herman Melville admonishes the reader: “for God’s sake, be economical with your lamps and candles! Not a gallon you burn, but at least one drop of man’s blood was spilled for it.”