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 wonderful than the building itself. Why didn't this mirror crack, and what was it? A polished steel reflector for the fire at night or for heliography by day? Some writers describe it as made of finely wrought glass or transparent stone, and declare that when they sat under it they could see ships at sea that were invisible to the naked eye. A telescope? Is it conceivable that the Alexandrian school of mathematics and mechanics discovered the lens and that their discovery was lost and forgotten when the Pharos fell? It is possible: the discoveries of Aristarchus were forgotten, and Galileo persecuted for reviving them. It is certain that the lighthouse was equipped with every scientific improvement known to the age, that it was the outward expression of the studies pursued in the Museum across the straits, and that its architect could have consulted not only Aristarchus, but Eratosthenes, Apollonius of Perga, and Euclid.

Standing on the lantern, at the height of five hundred feet above the ground, a statue of Poseidon struck the pious note, and gave a Greek air to Africa seen from the sea. Other works of art are also reported: for example, a statue whose finger followed the diurnal course of the sun, a second statue who gave out with varying and melodious voices the various hours of the day, and a third who shouted an alarm as soon as a hostile flotilla set sail from any foreign port. This last must belong to an even more remarkable building, the Pharos of legend, which we will measure in a moment. The lighthouse was the key of the Alexandrian defences, and Cæsar occupied it before