_Which marks, near the entrance to Boston Harbour, a rocky reef seldom seen above the surface of the water. From this spot, the famous old skeleton iron lighthouse that formerly marked the reef was swept by a gale in 1851._ ] If a reef lies near a course followed by ships a light must guard it. If a sand bank is hidden from the sight of ships that might ground on it a light must be there as a warning. If an island constitutes a menace because swift currents flow past its shores a light must tell the sailor where the danger lies. Nor are lighthouses useful only at night. In daylight they form conspicuous marks from which the navigator may learn his exact position. In fog their huge foghorns wail like lost souls, sending warnings far into the engulfing mist in order that sailors may hear and know that land is near. Then, too, each light is individual. One flashes regularly, one irregularly, one red and white, one red alone. Other lights are steady beams, but each can be recognized, and so they are like friendly faces, recognizable, every one. Perhaps the coast of France is the best lighted in the world. Certainly it would be difficult to imagine one with a more perfect system. I have sailed the coast of Brittany at night, fearful of the currents and the storms that often blow on the stormy Bay of Biscay. But always, to minimize the dangers of the rocky coast and hidden reefs, the lighthouses blinked, and the task is simple to determine one’s position any time, except in fogs. For the French have placed their lighthouses so that as a ship sails along the coast there are always at least two lights in sight at once. From these, cross bearings can be taken at almost any moment, and the careful navigator, in clear weather, need never feel uneasy as to his position. Ushant Island, that rocky islet just off the coast of Finisterre, was long a graveyard of ships—and still, from time to time, some ship is caught on its rocks—but now bold lights stand high above the smother of foam and the roar of breakers, marking the spot in order that ships may carefully give it a wide berth. Formerly every lighthouse had to have attendants, as the most important still have, but modern improvements are making unattended lights more and more common. One finds them everywhere. The rocky coast of Sweden, the firths of Scotland, the mountains of the Strait of Magellan, the gorgeous coast of Indo-China all have many of these new beacons.