THE AGE OF ARCHIMEDES

Archimedes, the first great inventor, lived in Syracuse more than two thousand years ago. Syracuse was a Greek city on the island of Sicily. The King of Syracuse, Hiero, took great interest in the discoveries of Archimedes.

One day Archimedes said to King Hiero that with his own strength he could move any weight whatever. He even said that, if there were another earth to which he could go, he could move this earth wherever he pleased. The King, full of wonder, begged of him to prove the truth of his statement by moving some very heavy weight. Whereupon Archimedes caused one of the King's galleys to be drawn ashore. This required many hands and much labor. Having manned the ship and put on board her usual loading, he placed himself at a distance and easily moved with his hand the end of a machine which consisted of a variety of ropes and pulleys, drawing the ship over the sand in as smooth and gentle a manner as if she had been under sail. The King, quite astonished, prevailed with Archimedes to make for him all manner of machines which could be used either for attack or defence in a siege.

The Battle of Syracuse

During the life of King Hiero Syracuse had no occasion to use the war machines of Archimedes. The grandson of King Hiero, who succeeded to the throne, was a tyrant. He attempted to throw off the sovereignty of Rome and entered into an alliance with Carthage. His cruelty toward his own people was so great that, after a short reign, he was assassinated. There was anarchy in Syracuse for a time, the Roman and anti-Roman parties striving for supremacy. The anti-Roman party gaining possession of the city, the Romans, in order to bring Syracuse again into subjection, prepared for an attack by sea and land. Then it was that Syracuse had need of the war machines made by Archimedes (Fig. 1).

The Romans came with a large land force and a fleet. They were sure that within five days they could conquer the city. But there are times when one man with brains is worth more than an army. In the battle which followed, Archimedes with his inventions was more than a match for the Romans.

The city was strong from the fact that the wall on one side lay along a chain of hills with overhanging brows; on the other side the wall had its foundation close down by the sea.

A fleet of sixty ships commanded by Marcellus bore down upon the city. The ships were full of men armed with bows and slings and javelins with which to dislodge the men who fought on the battlements. Eight ships had been fastened together in pairs. These double vessels were rowed by the outer oars of each of the pair. On each pair of ships was a ladder four feet wide and of a height to reach to the top of the wall. Each side of the ladder was protected by a railing, and a small roof-like covering, called a penthouse, was fastened to the upper end of the ladder. This covering served to protect the soldiers until they could reach the top of the wall. They thought to bring these double ships close to shore, raise the ladders by ropes and pulleys until they rested against the wall, then scale the wall and capture the city.

But Archimedes had crossbows ready, and, when the ships were still at some distance, he shot stones and darts at the enemy, wounding and greatly annoying them. When these began to carry over their heads, he used smaller crossbows of shorter range, so that stones and darts fell constantly in their midst. By this means he checked their advance, and finally Marcellus, in despair, was obliged to bring up his ships under cover of night. But when they had come close to land, and so too near to be hit by the crossbows, they found that Archimedes had another contrivance ready. He had pierced the wall as high as a man's head with many loopholes which on the outside were about as big as the palm of the hand. Inside the wall he had stationed archers and men with crossbows to shoot down the marines. By these means he not only baffled the enemy, but killed the greater number of them. When they tried to use their ladders, they discovered that he had cranes ready all along the walls, not visible at other times but which suddenly reared themselves above the wall from the inside and stretched their beams far over the battlements, some of them carrying stones weighing about five hundred pounds, and others great masses of lead. So, whenever the ships came near, these beams swung round on their pivots and by means of a rope running through a pulley dropped the stones upon the ships. The result was that they not only smashed the ships to pieces, but killed many of the soldiers on board.

Another machine made by Archimedes was an "iron hand" or grappling-hook swung on a chain and carried by a crane. The hook was dropped on the prow of a ship, and when it had taken hold the ship was lifted until it stood on its stern, then quickly dropped, causing it either to sink or ship a great quantity of water.

With such machines, unknown before, Archimedes drove back the enemy. On the landward side similar machines were used. The Romans were reduced to such a state of terror that "if they saw but a rope or a stick put over the walls they cried out that Archimedes was levelling some machine at them and turned their backs and fled."

After a long siege, however, hunger forced the Syracusans to surrender. Marcellus so admired the genius of Archimedes that he gave orders that he should not be injured. Yet, in the sack of the city which followed, Archimedes was slain by a Roman soldier.

The Roman historian Livy records that "Archimedes, while intent on some figures which he had made in the dust, although the confusion was as great as could possibly be, was put to death by a soldier who did not know who he was; that Marcellus was greatly grieved at this, and that pains were taken about his funeral, while his relations also were carefully sought and received honor and protection on account of his name and memory."

Archimedes' Principle

Hiero, when he became King of Syracuse, decreed that a crown of gold, of great value, should be placed in a certain temple as an offering to the gods, and sent to a manufacturer the correct weight of gold. In due time the crown was brought to the King, and a beautiful piece of work it was. The weight of the crown was the same as that of the gold, but a report was circulated that some of the gold had been taken out and silver supplied in its place. Hiero was angry, but knew no method by which the theft might be detected. He therefore requested Archimedes to give the matter his attention.

While trying to solve this problem Archimedes went one day to a bath. As he got into the bath-tub he saw that as his body became immersed the water ran out of the tub. He quickly saw how he could solve the problem, leaped out of the bath in joy, and, running home naked, cried out with a loud voice "Eureka! eureka!" (I have found it! I have found it!)

Using a piece of gold and a piece of silver, each equal in weight to the crown, and a large vase full of water, he proved that the crown was not pure gold, and found how much silver had been mixed with the gold.

The incident of the golden crown may have been the starting-point of Archimedes' study of solid bodies when immersed in fluids. Every one knows that a boy can lift a heavy stone under water that he could not lift out of water. The stone seems lighter when in the water. A diver with his lead-soled shoes could scarcely walk on land, but walks easily under water. When the diver comes up, the place where he was immediately becomes filled with water. Now, whatever that water weighs which fills the diver's place, just that much weight will the diver lose when he goes down. What is true of the diver is true of the stone or of any object under water. The stone when in the water loses just as much weight as the weight of the water that would fill its place. This is the fact which was discovered by Archimedes and which is called "Archimedes' Principle."

It is said by an ancient author that Archimedes invented more than forty machines. Of these the best known are the block and tackle, the endless screw (worm gear), and the water snail, or Archimedean screw. Yet his delight was not in his machines, but in his mathematics. Though he had invented machines to please his king, he regarded such work as trifling, and took little interest in the common needs of life.

Inventions of the Ancient Greeks

The common needs of life are to-day the chief concern of the greatest men, and so we find it hard to sympathize with this view of Archimedes. His view, however, was that of other learned men of his time, that the common needs of life are beneath the dignity of the scholar, and so we can see why the Greeks made so few great inventions.

Hero, who lived a century later than Archimedes, invented a steam-engine, which, however, was only a toy. A water-clock, in which the first cog-wheels were used, was invented by another Greek named Ktesibus, who also invented the force-pump. The suction-pump was known in the time of Aristotle, who lived about a century before the time of Archimedes, but the inventor is unknown.

Concerning electricity, the Greeks knew very little. They knew that amber when rubbed will attract light objects, such as dust or chaff. Amber was called by the Greeks "electron," because it reflected the brightness of the sunlight, and their name for the sun was "Elector." From the Greek name for amber we get our word "electricity."

The Greeks possessed scarcely more knowledge of magnets than of electricity. In fact, their ideas of magnets cannot be called knowledge, for they consisted chiefly of legends.

They told of the shepherd Magnes, who, while watching his flock on Mount Ida, suddenly found the iron ferrule of his staff and the nails of his shoes adhering to a stone; that, later, this stone was called, after him, the "Magnes stone," or "Magnet."

They told impossible stories of iron statues being suspended in the air by means of magnets, and of ships sailing near the magnetic mountains when every nail and piece of iron in the ship would fly to the mountain, leaving the ship a wreck upon the waves.