From this the Egyptians of early times probably adopted their idea of lights, that were burned every night at given spots near the shore, in order that ships might find their way by them. Such fires were tended in those early days by priests, and a priestly duty it was—and still remains, although simple, quiet people now tend the lights and consider it only a work to be done—but it is a work of infinite value to the world of ships in which most of the reward lies in the knowledge of a task well done. A Greek poet, writing about 660 B. C., mentions a lighthouse at Sigeum, a town near the site of ancient Troy, and this was one of the very earliest lighthouses regularly maintained. But in the years that followed this they probably became more and more numerous, and as their importance was recognized they became more and more similar in external appearance to those we know to-day. That this is probably true seems to be borne out by the erection at Alexandria, Egypt, about 275 B. C., of the famous Pharos, which, we are told, was 600 feet high and similar in shape to the minarets so common in Mohammedan lands to-day. That the structure was as high as it is said to have been seems doubtful, but that it was of extraordinary height is proved by its inclusion among the seven wonders of the ancient world. So impressive a lighthouse could hardly have been the first of its kind, although, no doubt, it far surpassed all others. At the top of this great tower a fire was kept burning, and for nearly sixteen centuries its great shaft stood the test of time, before it collapsed in an earthquake. Centuries before its end, however, the Mohammedan conquerors had come to be the rulers of Egypt, and near the top of this great tower a small praying chamber was placed. Perhaps from its great height the muezzin called the faithful to their prayers, and certainly its graceful lines left a deep impression on the Mohammedans, for from it came the idea that resulted in the erection of the numerous minarets that mark almost every Mohammedan city of the earth. And ere the convulsion of Nature toppled this striking edifice to the earth the idea of lighthouses had greatly widened, and widely separated lands had built lighthouses of their own to guide the sailor as he sailed the sea. Rome built many along the coasts her ships were forced to visit, one at Dover and one at Boulogne being, probably, the earliest on the shores of England and of France. Both of these are gone, leaving only traces of their existence, but the ruins of the ancient tower at Ostia, at the mouth of the Tiber, still remain to remind us of great galleys that were guided by its fire in the nights of the first century after Christ. At Corunna, Spain, there still stands an ancient Phœnician or Roman tower, known as the Pillar of Hercules, and from its top, in ages now long dead, a flaring beacon marked the spot for sailors far at sea.