Archimedes (287–212 B.C.), a half-century after Aristotle, developed at Syracuse, then a Greek colony on the island of Sicily, the first recorded light apparatus, “The Burning Mirrors or Lenses.” Famed as the first great geometrician, Archimedes is best known for his principle upon which all ship construction is based--the buoyant force exerted by a liquid is equal to the weight of the displaced liquid. In other words, a shaped object of metal, such as a ship, will float if it displaces a sufficient quantity of water. King Hiero of Syracuse, a relative of Archimedes, gave him the problem of determining whether or not a new crown he had received was made of pure gold, as ordered, or whether the gold had been mixed with silver. This would have been no task at all if the King had not been fond of the crown and wished the information secured without damaging it in any way. As was the custom in those days, Archimedes considered the problem one afternoon at the local bath which served the double function of promoting cleanliness and of fostering every kind of discussion. It was the gentlemen’s club of the day and place. Archimedes liked to bathe with a tub full of water and this particular afternoon he noted that a considerable amount of water was spilled over the sides of the tub as he stepped in. He immediately and correctly concluded that there was a relation between the mass of his body and the weight of the water displaced. Then according to tradition he rushed home, through the streets of Syracuse, naked, in order to test the King’s crown, shouting “Eureka--I have found it.” This talented Greek was keenly aware of his scientific prowess and was not a man to keep his ideas secret. He promised to lift the world with a lever (the principle of which he had developed scientifically) provided someone would furnish him a fulcrum. There were no takers. When Archimedes was 73 years old and respected throughout the civilized world for his work in mathematics and science, the Roman invader Marcellus lay siege to Syracuse. At the beginning of the two long years of struggle, Archimedes put aside his theoretical work and with the vigor of a youth helped to defend the city, inventing numerous engines of war for the purpose. In this he was the real pioneer of the scientists of our own day who perfected in wartime the atomic bomb, radar and other devices. Archimedes’ most important development in his martial pursuits was the Great Burning Glasses or Lenses upon which much of his fame has since rested. According to tradition, the Great Burning Glasses of Archimedes were used to burn the fleets of Marcellus, acting on the same principle used by the modern Boy Scout or woodsman in starting a fire with a pocket magnifying glass.