But all of these earlier lighthouses were built on dry land, sheltered by the shore from the crash of waves. It was the city of Bordeaux, on the Gironde River in France, that first built a lighthouse on a wave-swept rock to warn ships from its treacheries. [Illustration: THE PHAROS AT ALEXANDRIA _One of the seven wonders of the ancient world, and one of the first great lighthouses._] The Gironde River flows into the stormy Bay of Biscay, its wide mouth often filled with foaming waves driving in from sea, which crash upon a rocky reef that lies in the very centre of the estuary. So great a toll of passing ships was taken by these rocks that the thriving city of Bordeaux was like to lose its water-borne commerce, and to keep the trade that meant so much to the city the citizens agreed to mark the spot with a light. A simple tower was erected on this spot about the year 805. For years it served, until Edward the Black Prince, temporarily in control of the vicinity, erected a slightly greater tower. For a time this, too, was kept, but finally, an aged keeper having died, the fire was no longer lit. For many years the rocks remained unlighted, and then, in 1584, during the reign of Henry II of France, a new lighthouse was begun. For twenty-five years the work of construction was under way, and when it was completed it was the most magnificent lighthouse of all time. Nor has another been built since to equal it in magnificence. About its base a great stone breakwater was built, surmounted by a balustrade. The lowest floor of the structure contains a beautiful hall and an apartment originally intended for the king. Above is a chapel, beautifully designed and decorated, and above this stands the tower which contains the light. This, originally, placed the light about one hundred feet above the rocks. Later the tower was increased in height to 207 feet and now it is equipped with the most modern apparatus, visible in clear weather for twenty-seven miles, to take the place of the blazing log fire that for so long did its best to guide the mariners in from sea. Until the 18th Century the fires of these beacons burned wood, and then coal came gradually into use. The objections to such fires are obvious. They had no definite range, for fires died down or burnt furiously, and when a strong wind drove in from sea the fire was often all but hidden from sight of ships as it curled around in the lee of the tower. But America had been settled and had such lighthouses on its own coast ere other methods superseded this. The first lighthouse in the United States was the one on Little Brewster Island on the south of the main entrance to Boston Harbour. It was built in 1716, although the lighthouse now occupying that site was erected in 1859. During the Revolutionary War the structure was destroyed and rebuilt three times. The third structure was a stone tower sixty-eight feet high, and four oil lamps were used to illuminate it.