Archimedes

ar'ki-me'des (287-213 B. C.), a philosopher of Syracuse. He is supposed to have studied at the peculiar university connected with the Alexandrian library. While in Egypt, so it is said, he invented what is known as Archimedes' screw. It consists of a hollow tube, wound in a spiral fashion around a central cylinder. If the cylinder be placed in a slanting position, with the lower end of the tube under water, and the cylinder turned with a crank, water may be elevated through the spiral. This device was of use to the Egyptians in draining their lower lands after the overflow of the Nile. It is still in use in Holland, where water screws are turned by windmills to drain the lowlands behind the dikes. Archimedes, speaking of the lever, is said to have declared, "Give me a place to stand and I will move the world."

Archimedes is credited with the discovery of the principle known by his name, namely that if a solid be immersed in a liquid, the loss of weight by the solid is equal to the weight of the amount of liquid displaced. A cubic inch of silver and a cubic inch of gold immersed in a liquid displace a cubic inch each, and suffer an equal loss of weight; but a pound of gold occupies less space than a pound of silver. It therefore displaces less of the liquid and suffers a smaller loss of weight. When immersed in water, gold loses a little less than one-nineteenth of its weight; silver considerably more than one-tenth.

A story runs to the effect that King Hiero trusted an artificer with a quantity of gold out of which to make him a crown, but that, having occasion to doubt the honesty of the workman, he sent the crown to Archimedes for an examination. While in a public bath and noticing the height to which his own body caused the water to rise in the tub, it occurred to the philosopher that if he were to ascertain the loss of weight of gold in water, and compare it with the weight of the crown in water, he could determine the amount of gold that had been stolen and replaced by a baser and lighter metal. So overjoyed was he, so the story goes, that he sprang from the bath and ran home without a stitch of clothing, crying, "Eureka, Eureka! I have found it! I have found it!"

During the siege of his native city Archimedes is said to have set fire to a Roman ship with a burning glass. He perished at the hands of a common Roman soldier, who knew no better than to slay the greatest scientist of the day. Cicero, once appointed governor of Sicily, reported finding the tomb of Archimedes overgrown with briars. His monument bore an inscription of a cylinder in which a sphere was inscribed, a fitting testimonial to Archimedes' discovery of their relative magnitude.