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sink while light ones arise. All his statements relating to mechanics are erroneous and some are positively childish.

The first real student of mechanics was Archimedes (287-312 B.C.) To him we owe the foundations of the science. For example, to him we owe the theory of the lever, from which he developed the idea of the center of gravity. He was especially interested in the subject of hydrostatics, and established principles that are of universal application to-day. His practical applications are best illustrated in the engines of war which he devised to aid in the defense of Syracuse. So effective were these that the Romans took the city not by assault but by starvation. For fifteen hundred years thereafter practically no advance was made. In 1462 the Turks took Constantinople, and fugitive Greeks