The Ancient Engineers, page 14
By a surprise attack at night, Demetrios seized the main mole guarding the harbor. Here his master gunner Apollonios mounted huge catapults throwing 3-talent (180-pound) catapult balls. Demetrios tried to force the defenses of the harbor with troops from landing craft, covered by a heavy bombardment.
Though greatly outnumbered, the Rhodians fought fiercely and countered every move by the attacker. Their own ships broke through the spiked log boom with which Demetrios protected his engines and sank two of them. Demetrios prepared a super-tower mounted on the hulls of six galleys, but a storm overturned this engine as it was being towed into position, and the Rhodians took advantage of the storm to recapture the mole.
Then Demetrios attacked from the land side. He built eight tortoises or wheeled sheds to be pushed up to the wall to protect the engineers while they filled up the ditch and undermined the wall. He built two enormous ram tortoises, each housing a ram 180 feet long and worked by a thousand men.
Demetrios' largest war machine was a colossal belfry designed for him by the engineer Epimachos. Different accounts give it different sizes, but it seems to have been 100 to 150 feet high and 50 to 75 feet square on the base. It had nine stories, each loopholed for catapults to shoot through. The loopholes were protected by shutters in the form of big leather cushions stuffed with wool, which could be raised from within. Inside were two sets of ladders, one for traffic up, the other down. On each level stood a water tank with buckets for putting out fires. The whole contraption was pushed on eight huge iron-tired, castor-mounted wheels by 3,400 of Demetrios' strongest soldiers.
Demetrios moved his engines forward and attacked the wall, but the Rhodians beat back the efforts of his men to swarm through the gaps. Then the Rhodians moved all their catapults to one section of the wall and, by showering the belfry with incendiary missiles in a sudden night bombardment, set it afire.
By the time Demetrios had pulled his engines out of range, repaired them, and prepared to attack again, the Rhodians had another trick up their sleeves.
Before the war began, the municipal architect of Rhodes had been Diognetos. A Phoenician, Kallias of Arados, came to Rhodes and lectured on his wonderful new machine for defending cities. This was a revolving crane to seize hostile siege engines, hoist them into the air, and drop them down again inside the city. Impressed, the Rhodians fired Diognetos and gave Kallias his job.
So, when Demetrios' 180-ton monster neared the city, the Rhodians told Kallias to go ahead with his revolving crane. But Kallias had to admit he was baffled. Then the Rhodians fired Kallias and begged Diognetos to take his old job back. After holding out for a while, Diognetos agreed to save the city on condition that he should have the belfry if he could capture it.
One account says that he mobilized the Rhodians to go out at night and pour liquids—water, mud, or sewage—into the ditch in front of the section of wall at which the belfry was aimed. The adjacent field thus became a bog, in which the advancing tower stuck fast. Another story says he tunneled under the field. When the wheels of the belfry passed over these tunnels, the wheels sank into the ground. In any case, the belfry was stopped. Demetrios launched more attacks, but without artillery support these were beaten off.
At last, after a siege of more than a year, Demetrios signed a treaty with the Rhodians and sailed away to other battles. At Thebes he built a belfry so heavy that it could be moved only a quarter of a mile in two months.
Diognetos brought the captured belfry into the city and set it up in a public place with an inscription:
DIOGNETOS DEDICATED THIS TO THE PEOPLE
FROM THE SPOILS OF WAR
Afterwards, the Rhodians sold the timber, bronze, and iron from Demetrios' war engines and used the money to build the Colossus of Rhodes, a 100-foot statue of the sun god, to whom they had prayed for deliverance.
Centuries later, a stone thrower of a new type appeared. This had a single arm which, impelled by a torsion skein, flew up in a vertical plane against a padded stop. At the end of the arm was a sling or spoon to hold a catapult ball. This engine is called an onager (Latin for the
Asiatic wild ass) because of that animal's mythical habit of kicking stones back at its pursuers. All that is known about the origin of the man-made onager is that it came into use some time in the first three centuries of the Christian era. In any case, it soon replaced the heavy two-armed stone thrower.
Under the Roman Empire, armies also used light catapults on wheels as field artillery. They were not very effective, because they were too heavy and bulky in proportion to their fire power. Such mobile catapults had been tried out as far back as —207 by the Spartan general Machanidas. But at the battle of Mantinea, the Spartans lost to the Achaean League and Machanidas was slain before the catapults had a chance to shoot.
Ancient armies did not usually carry complete large catapults with them, because such bulky objects would have slowed them down too much. Instead, the gunners brought along the skeins, slings, metal fittings, and other parts that could not be improvised. Then, when a siege began, they cut down trees and built their engines on the spot.
With the fall of the West Roman Empire in +V, the two-armed torsion catapult drops out of sight. Perhaps the decline of European engineering at this time made the building of so complex an engine impractical. However, the flexion dart thrower, with a solid bow, continued in use through the Dark and Middle Ages. It was used at the siege of Rome by the Goths in +537 and at that of Paris by the Northmen in +886.
After printed treatises on ordnance began to appear during the Renaissance, and after cannon had already made catapults more or less obsolete, engineers like Leonardo da Vinci and Agostino Ramelli (+XVI) still showed catapults of the crossbow type in their books. One of Ramelli's designs is that of a compound siege catapult with six bows. Biringuccio, writing in the 1530s, notes that explosive bombs "can also be thrown from ballistas as the ancients used to do or, if desired, with guns as the moderns do." Biringuccio's "ancients" are the technicians who lived more than a century before his time.24
While the two-armed torsion catapult disappeared in the West, the crossbow survived there. A simple hunting crossbow is shown on two monuments of Roman Imperial times in Gaul, and William of Normandy took a company of crossbowmen to the battle of Hastings. On the other hand, the crossbow died out in the East. Although a tenth-century Byzantine writer mentions it, by the time the Crusaders brought it to Constantinople, in +XI, the Byzantines looked upon it as a new weapon.
The onager also survived into the feudal era. At that time it was
called the mangon or mangonel, from the Greek manganon, "device" or "contrivance." It decided the outcome of one battle at least. During the Albigensian Crusade, in 1218, Simon de Montfort besieged Toulouse. While he was riding around the city walls one day, a crew of women, manning a mangonel, let fly at him. The stone smashed his head like an egg and ended the siege.
The onager in turn gave way to the trebuchet or counterweight catapult, first mentioned in Spain in early +XII. The trebuchet had a pivoted throwing arm with a sling on the long end and a heavy counterweight on the short. This catapult had the advantage over skein-powered catapults that wet weather did not affect its performance. Sometimes the range could be adjusted by varying the size of the counterweight or by shifting the counterweight towards or away from the fulcrum. Sometimes the counterweight was assisted by a crew of soldiers, pulling on ropes attached to the short end of the throwing arm. In a catapult of a very simple type, men, pulling on the short end of the arm, provided all the energy.
Knowledge of catapults also reached the Far East. They were known in China by 1004 and in India by 1300, and there were literary allusions to the catapult or pau in China several centuries before +1000. When the Polo brothers first visited the court of Kublai Khan in the 1260s, the Italians charmed the Mongol emperor by building much larger catapults than the Mongols were used to, throwing 300-pound stones, for use against the city of Hsyang-yang. One missile smashed a house to kindling and caused the city's surrender. In Chinese chess one piece is still called "the catapult." The Cambodian kings who built Angkor mounted small catapults on elephants.
On the other hand, China knew the crossbow even before it was invented in the West. Writing in early —V, the Chinese general Sun Wu25 mentions the weapon. And when in —35 the impetuous Chinese general Chen Tang defeated and slew the troublesome Hunnish king Jiji",26 the Chinese army used crossbows. This is undoubtedly a case of independent invention.
Soon, however, the whole art of catapult artillery was swept away by the discovery that "This villainous salt-petre" could "be digg'd / Out of the bowels of the harmless earth," and that "these vile guns,"27 even in their crude fourteenth- and fifteenth-century forms, multiplied the power of the bombardier many times over.
So ends the story of Greek engineering, from the beginnings of classical history down to the time of Alexander. All in all, to the Greeks of that period, we owe more in the fields of art, literature, philosophy, logic, politics, and pure science than in the field of engineering. But neither was their engineering negligible. Moreover, Dionysios' brilliant and sinister idea of hiring men to invent machines of war was to persist down the ages and to culminate in the vast and secret military research and development projects of today.
In the period after Alexander, the comparative backwardness of Greek engineering, compared with the Greeks' other attainments, came to an end. Soon the Greeks—though usually living outside of Greece-led the world in this respect, as we shall presently see.
FIVE
THE HELLENISTIC
ENGINEERS
In —IV, Alexander son of Philip, king of Macedonia, subdued all of Greece. Then he led an army of Greeks and Macedonians to the conquest of the mighty Persian Empire. From the rocky shores of Ionia, his columns pounded past the bustling Phoenician seaports to the shimmering sands of Egypt, and from Egypt to the ancient ziggurats of Mesopotamia, the tiger-haunted jungles of Hyrkania, and the lonely steppes of Central Asia.
The Persians, ruled by a well-meaning but hesitant mediocrity of a king, were smashed in three thunderous battles and many sieges and skirmishes. Having taken the throne of the King of Kings, Alexander led his army of Macedonians, Greeks, and Persians over the Afghan crags and into the Indus Valley to vanquish the glittering rajas and their lumbering elephants.
By —323, Alexander had conquered a realm as great as that of the first Darius. He had encouraged the intermarriage of Macedonians with Persians and had laid grandiose plans for further conquests, explorations, and public works. Then, not yet thirty-three, he suddenly died of (probably) malaria, in Babylon.
Alexander's generals soon liquidated the conqueror's kinsmen and carved up his empire. The leading kingdoms of the Successors were Egypt, under the Ptolemies; Macedonia, ruled by the descendants of Demetrios Poliorketes; and the Seleucid kingdom—Syria, Mesopotamia, and Iran—under the line of the general Seleukos. Several kingdoms waxed and wailed in Asia Minor, of which the most important was Pergamon.
Although most of Alexander's Macedonian officers soon discarded the Persian wives he had found for them, his hoped-for mixture of Greeks with orientals soon took place anyway. Alexander and the Successors founded scores of new cities in the conquered lands. They encouraged thousands of Greeks and Macedonians to settle in these cities side by side with Persians, Syrians, Egyptians, and other native peoples. Hellenes swarmed out of barren Greece to serve in the armies and bureaucracies of the Successors, forming a ruling class in the new kingdoms.
The interloping Greeks soon mingled with the native upper classes. Greek culture influenced the orientals, while oriental ideas affected the Greeks. The brilliant Graeco-oriental civilization that resulted is called the Hellenistic.
The Hellenistic Age was in many ways like our own century. It was a time of immense intellectual ferment, of travel and tourism, of scholarship and research, of popular outlines and lectures, of clubs and societies, of invention and promotion. It was a time on one hand of a scramble for the wealth created by the advance of technology and the spread of commerce, and on the other of communistic revolutionary movements for the division of this wealth. Some of the fine arts, such as playwriting, declined from the high standards of the Golden Age; but science and engineering flourished as never before.
Another "modern" feature of the Hellenistic Age was a love of the grandiose. Hellenistic kings armed their soldiers with longer spears and massed them in bigger phalanxes than ever before; they built more sumptuous temples and palaces; they erected taller buildings and statues; they organized more splendid parades and committed more dastardly crimes.
The Successors and their descendants fought many wars, but these wars were less ferocious and destructive than many wars have been. The kings fought the other Hellenistic kings—usually their brothers-in-law—in a somewhat sporting, gentlemanly spirit. They tried many novel military expedients: huge phalanxes on the Macedonian model, with the soldiers wielding 21-foot pikes; elephants, which often defeated their own side by stampeding back through the ranks; even Arabs swinging 6-foot swords from the backs of camels.
As metalworking techniques advanced, iron began to take the place of bronze for armor. Alexander the Great is the first man known to have worn an iron helmet. Dionysios the Elder of Syracuse, who invented the ordnance department, had already pioneered with the iron corselet, which he wore under his tunic to foil assassins. By the end of —IV, the iron cuirass had become common. To save weight, however, most classical cavalrymen continued to prefer a corselet made of several layers of linen canvas glued together and molded on a form; the result was much like a modern laminated plastic.
Meanwhile, in the little-known West, Rome grew from city-state to nation and from nation to empire, until it engulfed the entire Hellenistic world. In —30, Rome conquered the last of the Successors' kingdoms, Egypt, and brought the Hellenistic Age to a close. But, for three centuries, the lands of the eastern Mediterranean were the scene of some of the liveliest and most interesting developments in the entire history of ancient science and technology.
In addition to Alexander, another man had an equal effect on the flowering of Hellenistic science and engineering. This was Alexander's old tutor, Aristoteles of Stagyra (—384 to —322), whom we call Aristotle. By his researches, writings, and teachings, Aristotle gave all the sciences a push so vigorous that it kept them spinning for centuries.
Few men have affected the thought of the world more than Aristotle. He was the first encyclopedist and also the founder of the scientific method. His method was neither pure theorizing, like that of Plato, nor the mere gathering of data, like that of Herodotos. Instead, he creatively combined both. Although Aristotle often went wrong in applying the scientific method, he made the necessary beginning.
At seventeen, Aristotle arrived in Athens from a Greek provincial town at the northwest corner of the Aegean Sea. He joined Plato's classes and for twenty years listened to Plato's discourses. He may even have become Plato's assistant. There are rumors that Aristotle once quarreled with Plato and tried without success to set up his own school; but their differences were soon patched up.
After Plato died, Aristotle and his fellow-pupil Xenokrates crossed the Aegean to settle at Assos in Asia Minor. Here Aristotle began lecturing. One of his hearers was a local magnate, Hermias the eunuch, who had become tyrannos of the town of Atarneus. Aristotle married Hermias' niece and took his bride to Lesbos for two years of honeymooning while studying marine biology. It would be interesting to know what the princess thought of a husband who spent his days wading in tidal pools and his nights cutting up sea-things on the kitchen table.
In —342, Aristotle heard that Philip II of Macedon was looking for a tutor for his son Alexander. Aristotle got the job, either because his father had been physician to Philip's father or because he played a part in a plot between Philip and Hermias against the latter's Persian overlords.
In any case, the Persians discovered the plot and killed Hermias. For seven years, in a small Macedonian town, Aristotle tutored Alexander and the latter's young friends. We do not know just what Aristotle taught Alexander, or how effective his teaching was; but it is not likely that he found the headstrong and violent young prince a docile or studious pupil.
When Philip was murdered and Alexander became king, Aristotle went back to Athens. Since Xenokrates was now running Plato's school, called the Academy from the name of the park where it met, Aristotle set up his own school in another park, the Lyceum.1 This school was also known as the Peripatetic because, like Plato, Aristotle liked to walk about as he lectured.
Here Aristotle taught and wrote for thirteen years: a lean, dandyfied man with a lisp and a tart sense of humor. Once, when a chatterbox, after flooding Aristotle with talk, asked:
"Have I bored you to death with my gabble?"
Aristotle replied: "No, by Zeus, for I wasn't listening to you!"2
When Alexander conquered the Persian Empire and invaded India, he may have subsidized Aristotle's researches. There are tales that Alexander sent Aristotle an elephant and other specimens from the East. But their relationship was soured by the fate of Aristotle's nephew Kal-listhenes, who had gone off to the East as a member of Alexander's staff. The headstrong and tactless Kallisthenes irked Alexander by refusing to worship him and by making a public scene over the matter. Alexander accused Kallisthenes of treason and had him thrown into prison, where he soon died.
During his Athenian period, Aristotle wrote nearly all of his works that have come down to us. He was one of the world's most prolific writers, composing the equivalent of 50 to 100 modern books. But, of this huge output, we have only a fraction. Most of what we have consists of huge treatises—actually, a series of extended lecture notes—on science, politics, history, morals, and literary criticism.
