They flash accurately at regular intervals. They light their lights at dusk and turn them out at dawn. Some roar through the fog with their great warning voices, and all of this is automatic or semi-automatic. So far as the lights themselves are concerned they require no attention for months at a time. The sun turns them off as it rises in the morning, and as it sets, the delicate apparatus that its light expands contracts once more and the light is turned on. From time to time a tender visits each of these. The apparatus is overhauled, the supply of fuel renewed, and again for months the light performs its task. Nor are all lights placed in lighthouses. Many spots require other means, and lightships have been designed and built to perform the duties of lighthouses where lighthouses cannot be built. [Illustration: BISHOP ROCK LIGHTHOUSE _On a cluster of rocks off the Scilly Islands near the entrance to the English Channel where converge the most important of all the world’s shipping lanes._ ] To transatlantic travellers perhaps the most familiar of these is the Ambrose Channel Lightship, that rolls and pitches at its anchor outside the entrance to New York Harbour. But the most famous lightship on the American coast is the one that marks Diamond Shoal, that infamous spot just off Cape Hatteras. Several times the Government has attempted to build a lighthouse on this shoal, but the attempts have invariably been frustrated by the sea. A lighthouse does mark the Cape, but Diamond Shoal runs out beneath the stormy water for about nine miles from the Cape, and it is this dangerous sand bank that the lightship guards. Four and a half miles out from the bank the lightship is anchored in a stretch of water that has hardly a peer on earth for the frequency and suddenness of storms. Here this little ship jerks at her anchor, pounded by great seas, tugged at by swift currents, swept by fierce winds. She rolls and pitches, shipping seas over this side and then that, and jerking—always jerking at her cable. There is no easy smoothness to her roll as there is with a free ship at sea. There is no exhilaration to her pitch as she rises over the seas and plunges to the troughs, for always the jerk of the cable interferes, and from one month’s end to the next the little crew endures the discomfort and the hard work, in order that ships may be warned away from the treacherous sand of Diamond Shoal. These sturdy little ships do mark other things than dangers. In many cases they are the modern counterparts of the beach fires of those early peoples which lighted belated boats in to shore. To-day, however, those lightships which perform this task swing at their anchors outside the entrances to harbours, marking the channel through which the ships must pass on their way in from sea.