**Archimedes** (*är-kĭ-mē' dēz*)**,** a Grecian engineer, physicist, and mathematician, born at Syracuse, on the island of Sicily, about the year 287 B. C. What little is known concerning the details of his life is contained in the histories of Polybius, Plutarch and Livy and in the treatise on architecture by Vitruvius.

Like many men of science belonging to this period, he was educated at Alexandria.

His principal contributions to learning are (1) a large number of geometrical theorems; (2) a short treatise on arithmetic called *Psammites*, because grains of sand were used in the computations; (3) a determination of the centers of gravity in bodies of various shapes, a work which may be fairly called the foundation of modern statics; (4) a treatise on floating bodies; (5) in addition to the above, it is probable that he invented the screw which goes by his name and that he devised a hydrometer by which he could compare the densities of liquids.

Many stories have come down to us concerning his engineering feats at Syracuse while that city was besieged by the Romans during the second Punic War. Most of these stories are not well authenticated.

The best known perhaps is that told by Vitruvius. Having been assigned the problem of determining whether a certain crown supposed to be made of pure gold had been alloyed with silver, he devised the following method: First he measured the volume of a mass of gold just equal to the mass of the crown. This he did by putting the gold in a vessel of water and measuring the overflow. The second step was to measure, in the same way, the volume of a mass of silver just equal to the mass of the crown. Lastly he measured the volume of the crown which proved to be intermediate between that of the gold and that of the silver. From these data it was a simple matter to compute the percentage of silver in the crown. This method, it is said, suggested itself to him as he was getting into his bath, where he observed that the rise of water on the sides of the tub was apparently proportional to the volume of his body immersed.

The story goes on to relate that Archimedes announced this discovery by running through the streets, clothed principally with enthusiasm, and shouting "Eureka! Eureka!" (I have found it.)