By the beginning of the 1800s, Bell Rock in Scotland’s Firth of Forth was responsible for wrecking numerous ships each year. In just one of such wrecks, 491 sailors were killed. It was clear to everyone that sailors needed to be warned about Bell Rock. But since the Rock was 11 miles from shore, and submerged by the sea for all but two hours a day, most all the experts believed it would be impossible to construct a to build a lighthouse there. For Robert Stevenson, the challenge of building a lighthouse on Bell Rock—in order to improve his corner...