WHEN Alexander the Great overcame the Egyptians, he sailed along the African coast past the mouths of the river Nile until he came to a place which seemed to him suitable for building a great city. It was a strip of land on the sea-shore with a great lake behind it and an island in front. “Here,” said the mighty conqueror, “shall be my capital city, to be called Alexandria after my name.” So he sent for his great architect Dinocrates, and told him to plan the streets and palaces of the new royal city. Thousands of slaves were soon set to work. The streets were made straight and wide, and canals were dug to join the lake to the open sea and to the Nile, so that great merchant vessels would find shelter from the storms. The island was joined to the city by a causeway a mile long, and a lighthouse 400 feet high was built on the island. The lighthouse was in the shape of a round tower. On the top of the tower a bright fire was kept constantly burning, so that the smoke by day and the flame by night should guide ships safely into the harbour. This tower was the first lighthouse ever built, and is said to have cost a quarter of a million pounds (£250,000). Within fifty years of its foundation Alexandria became one of the foremost centres of commerce. The second of the Egyptian kings founded the famous Library of Alexandria, and thus secured for the city a place in the front rank of learning, which it kept for six hundred years. Many of the great works of Greek writers were saved from destruction by being preserved in Alexandria. The third king compelled every stranger who passed through Alexandria with a book in his possession to leave a copy of it at the Library. He also built a Museum, which was an institution closely resembling what we should now call a University. It had dwelling-rooms for professors, it had lecture halls, and a great dining-room. The University grew and flourished, and attracted clever young men from all the shores of the Mediterranean Sea. One of these students was Euclid, who wrote the books on Geometry. There were also poets, critics, and historians. Many books from all nations were translated into Greek, including the Old Testament, at which seventy scribes are said to have worked.