The Ancient Engineers, page 42
The landscape of Europe and the northern Mediterranean lands was dominated by these casdes and their surrounding farms, carved out, as it were, from the primeval forests and worked by miserable serfs. Paths, rather than roads, wound past these castles and on toward the occasional walled town, which was prepared to hold its own against the warring sieurs.
When the Crusaders conquered the Byzantine Empire in 1204, they carved the Empire up into feudal domains and dotted the mountain tops of Hellas with castles, whose ruins still rise jaggedly hither and yon against the clear blue sky. One of the world's largest and best preserved casdes, Kerak des Chevaliers, was built in Syria for the Knights Hospitallers of St. John of Jerusalem in the late +XII. It is curious that the best example of medieval European castle architecture should stand today in a Muslim land, while the finest medieval Muslim palace, the Alhambra at Granada, is in Christian Spain.
The art of pre-gunpowder fortification reached its peak in medieval Europe. Although most of the elements of the European castle—the round tower, the crenelated parapet, the moat, and the portcullis-were old, medieval castle-builders combined them with greater skill and care than their predecessors.
In fact, medieval castles reached such a pitch of perfection that few, before the coming of cannon, were ever captured save by surprise or treachery. As in the First World War, defense had a strong if temporary advantage over offense. Hence most wars took the form of indecisive sieges. The besieger tried to starve out the besieged. But, if the latter had prudently prepared for the siege, the attacker might well have to give up first when his men's short enlistments ran out and they trickled away.
Along with the other arts and sciences, fortification had declined in Europe during the Dark Ages. But then it began to revive. At the time of the Norman conquest of England (1066) the typical castle was no more than a large house of stone or wood, surrounded by a wooden stockade, on a mound surrounded by a ditch.
However, some larger and stouter castles had also been built, with turrets and crenelated parapets on the old Roman model. When the Crusaders saw the vast walls of Constantinople, they brought back to western Europe ideas for still more stubborn strongholds.
The medieval castle threupon developed two main features: a tall, thick, crenelated stone wall, the enceinte, surrounding the whole; and a large thick-walled round tower, the keep or donjon, for a last stand. The biggest keep of all was that of Chateau Coucy, near Soissons, 100 feet in diameter, 180 feet high, and made of walls 18 feet thick. In the First World War, General Erich Ludendorff ordered it blown up, not for any military reason but for the pleasure of destroying things.
The living quarters of early medieval castles, for the most part extremely crude and uncomfortable, were tucked away in odd corners of the structure. Provisions for warmth, cleanliness, and privacy were rudimentary.
The enceinte comprised the main defense. But, if it were overrun, the defenders retired into the keep. As the keep had only one small door and was of such massive masonry that it could not be battered down, the defenders could hold out there as long as their provisions lasted. On the other hand, the attackers could just as easily prevent the defenders from coming out.
As a result of crusading experience, castle builders changed from the simple enceinte-and-keep plan to one of concentric walls. Such a structure was really two or three castles, one inside the other. As one line of walls was taken, the garrison retired to the next. Because the inner walls were taller than the outer, missile troops on an inner wall could prevent the enemy from using an outer wall to attack an inner one.
In the later Middle Ages, the keep was revived, but its purpose was now different. The soldiers of the castle owner were likely to be mercenaries instead of feudal retainers. The main purpose of the keep was now to enable the lord to defend himself against his own men-at-arms in case they took it into their heads to cut his throat and share his wealth.
Castle architecture varied according to local conditions. Castles built in lowlands near running water were usually protected by moats. The most remarkable of these waterborne castles is the Pfalzgrafenstein, which rises like some strange stone ship from a low island in the Rhine.
In the mountainous parts of Germany and Austria, on the other hand, castles were perched on the most inaccessible crags. Such castles were so difficult for attacker* to reach that the owners could afford the luxury of windows in the outer walls. In northern lands, turrets were often surmounted by conical wooden roofs, like witches' hats, to ward the warriors on the battlements against bad weather.
Entrance to a castle was planned to daunt the most determined attacker. If a moat surrounded the castle, the moat was crossed in peaceful times by a drawbridge. The drawbridge is ancient; the Egyptian fortress at Buhen, in Nubia, had a drawbridge that moved on rollers about —2000. In medieval times the drawbridge was raised by chains wound around drums, which were turned by a windlass and gearing. When the drawbridge was raised, the assailants could not cross the moat unless they could drain it or fill it with earth or brushwood. To try to tunnel under it would be to drown the sappers.
If the besieger succeeded in crossing the moat—or climbing the crag, if the castle were perched on a mountain top—he next faced the portcullis. This was a heavy iron gate, lowered from a slot over the entranceway to bar further passage. The portcullis goes back to —IV, when Aineias the Tactician wrote:
And if a large number of the enemy come in after these fugitives and you wish to stop them, you should have ready above the center of the gate a portcullis of the stoutest possible timbers overlaid with iron.7
In Aineias' time, iron was still too costly to make a whole portcullis of it, so he advised iron-sheathed wood. Medieval portcullises, however, were of solid iron.
Besides the drawbridge and portcullis, entrance to a castle might also be strengthened by strong outer gate towers that constituted a small fortress in themselves. Mastiffs or bears might be chained at the outer gate to discourage unwanted visitors.
If an attacker overcame the defenses at the outer gate, he often found that he had to follow a spiral path around the castle to the main gate. The spiral went clockwise so that the attackers' shields, on their left arms, were on the side away from the inner wall and so did the assailants no good.
The cannon, invented in China or Germany, put an end to the castle-building art, or at least transformed it beyond recognition. During its first century, the cannon was so feeble that it had little effect on fortifications. The chronicler of the city of Ulm briefly noted in his entry for 1380: "A knight came and besieged the town and shot at it with thunder guns. It did no harm." A little siege now and then was the sort of thing you had to expect in those days.
However, the gun improved along with all the other devices of the time. By 1414, cannon were formidable enough so that the Elector of Brandenburg and Prussia was able in two days to demolish the castle of a rebellious noble. Soon castle walls were seen to be of no more avail against heavy artillery than magical spells. Lords converted their castles to more or less comfortable mansions and palaces. After the Turkish sultan, Muhammad II, took Constantinople in 1453 with his mighty artillery, it looked as though no stronghold could withstand the new weapon.
After the Turks conquered the Balkan peninsula and Hungary, they besieged Vienna in 1529. Vienna was then under the rule of Emperor Charles V, who reigned over a patchwork empire that included nearly all of western Europe save France and the British Isles. The wall of Vienna was a crumbling little thing only six feet thick, and there was no time to build a proper wall. So Count Salm, the Emperor's general, made the Viennese build thick earthen embankments instead.
Although the Turks outnumbered the defenders by ten to one and were deemed the world's bravest and best-disciplined soldiers, the defenders nevertheless beat off their fiercest attacks, while the sultan's cannon balls buried themselves harmlessly in the embankments. After a month of trying, the Turks gave up and marched back home.
The lesson of Vienna was soon learned. Engineers, notably Michele Sanmichele, invented a fortress of a new kind, with a polygonal or star-shaped plan, a low ground-hugging profile, and huge earthen ditches and embankments.
Machinery also advanced in medieval Europe. Europeans used catapults and crossbows much like those of classical times, save that for throwing heavy stones the counterweighted trebuchet took the place of the classical onager and the two-armed stone thrower.
In the late Middle Ages, for sieges and shipboard fighting, Europeans developed a heavy crossbow as powerful as the much larger dart throwers of classical times. This weapon had a steel bow. Much too stiff to be bent by hand, it was cocked by clamping a windlass with a rack and pinion gear over its butt and cranking the windlass to draw back the string.
Use of these powerful crossbows in open warfare, however, did not prove successful because of their slow rate of fire. For example, the English longbowmen routed the Genoese crossbowmen at Crecy (1346). Although the Genoese ^weapons were probably more powerful and accurate, the English archers shot so fast that they pincushioned the Genoese before the latter could make much impression, and a volley from three small English cannon completed the rout of the mercenaries.
Among the other machines of medieval Europe, we have seen how clocks evolved from the water clocks and geared astronomical computers of antiquity, with the addition of the escapement from China. Other mechanical advances were the combination of the crank and the foot treadle, applied to turning the lathe and the grindstone.
The advance of machinery was hindered by the guilds. The main purpose of the guilds was to make life easy for the master craftsmen who dominated them. The guilds kept out competition, restricted entry into the guild, and opposed innovations that might upset their business. They enjoyed political power through their representation on the councils of self-governing cities and thus were able to legislate against innovations.
An example of guild activity is the case of Hans Spaichl, a coppersmith of Nuremberg. In 1561, Hans invented an improved lathe slide rest. Hearing of this, the agitated Council showered Hans with commands: he should make no more such lathes until a committee had examined his first one and reported whether it might harm the city; he should not sell lathes to anybody outside his own craft; he should not leave town without permission. The Council offered Hans 100 florins if he would agree to let them destroy his lathe, which had cost him 300 florins to build, and promise to make no more like it.
After the case had dragged on for years, Hans built another lathe and sold it to a goldsmith, but the Council seized and destroyed it. When, some years later, another coppersmith built and sold one of the improved lathes, the Council decreed that "he shall be imprisoned in a barred dungeon for eight days to teach him not to do it again."9
Despite such handicaps, the design of machinery forged ahead. The most notable advances occurred in the millwright's art. From the medieval millwright, the mechanical engineer of later times evolved.
Medieval Europe inherited three types of water wheel from the classical world: the undershot, the overshot, and the horizontal. These continued in use with small improvements; see for instance the reversible overshot wheel depicted in Agricola's mining treatise (PL XXI). By moving the spout at the top, one could direct the flow of water into either of two sets of buckets around the rim of this wheel. One set of buckets turned the wheel one way and the other set the other way.
A sore point in the conflict between the medieval social classes was the feudal lords' assertion of a monopoly on grinding grain within their demesnes. All yeomen, tenants, and serfs were supposed to bring their grain to their lords' mills to have it ground at a price set by the lord. They were not even supposed to grind their own grain with querns in their own houses. The peasants paid no more heed to these rules than they were compelled to; hence much of the flour milled in medieval Europe was bootleg flour ground in illegal private mills.
In 1274, for example, St. Albans Abbey at Cirencester, England, asserted a feudal monopoly of the milling in Cirencester and demanded that the townsfolk surrender their querns. Fifty years later, the townspeople attacked the Abbey with arms and extorted from the Abbot the right to own their own querns. A few years later, the Abbot swooped on the town with his bully boys, searched the houses, and broke all the querns he found save a few that he carried off to pave the parlor floor of the abbey. Quarrels over milling rights dragged on for centuries, and some of these medieval monopolies were not finally done away with until +XIX.
The biggest medieval stride in the use of water power was not so much in the wheels themselves as in the uses to which they were put. In ancient times, water power was used only for milling grain and raising water, save for Ausonius' solitary mention of a water-powered sawmill.
The next mention of a water-powered sawmill comes eight centuries later. It is a sketch in Villard de Honnecourt's notebook (+XIII). The saw is hung by one end from a sapling braced at an angle and attached to the ground by a wooden linkage at its lower end. Four spokes on the mill-wheel axle push down the linkage as the wheel turns, and the spring of the sapling pulls the saw up again each time. This looks like a crude preliminary design that would not work in practice.
All we can say for certain about the origin of the water-powered sawmill is that it may have existed in some form from the time of Auso-nius to that of Villard, but we know nothing of how these mills worked. In the century after Villard, however, allusions to water-powered sawmills become common in France and Germany. Nevertheless, as late as 4-XVII and +XVIII, when some enterprising Englishmen tried to set up such mills in England, the mills were wrecked by mobs of hand sawyers, who feared that their bulging muscles would become obsolete.
During the Middle Ages, water power was also applied to the bellows of smelting furnaces, to trip hammers for crushing ore in smelteries and bark in tanneries, to fulling mills, and to grinding and polishing armor and other metal wares.
Horses and mules algo powered these machines by an apparatus called a horse whim. The animals were hitched to the ends of booms 10 to 15 feet long, or to the rim of a wheel of 10- to 15-foot radius. They could now work much more efficiently than in ancient times. For one thing, with the horse collar they could pull four times as hard. For another, they were allowed to walk around a big enough circle so that they could make full use of their strength.
The biggest novelty in European power machinery, however, was the windmill. The origin of the European windmill is another mystery. In 4-1, Heron of Alexandria proposed to power a hydraulic organ by means of a litde windmill or pinwheel. Nine centuries later, the Iranians of Seistan built windmills to mill their grain.
Now, Heron's pinwheel had a horizontal shaft, like windmills of the familiar European type; whereas the Persian windmill, as we have seen, had a vertical shaft like a revolving door. That was all very well in Seistan, where the wind blows for months from one direction. But it would not be practical in Europe, where the wind blows every which way. Therefore European windmills had to be pivoted, so that they could turn to face the wind.
The earliest trustworthy accounts of windmills in Europe dated from 4-XII. These windmills are of a type called the post mill. On a pedestal is mounted a small room, roughly cubical, so that it can be turned in any direction by means of a long wooden boom. The room contains the millstones, driven through gearing by a shaft that projects through the wall of the room and carries the sails. The sails may be of wood or a combination of wood and cloth.
The number of sails varied. There were usually four sails, but sometimes there were six or eight. They were usually adjustable for different wind velocities.
Along the northern shore of the Mediterranean, a type of mill still in use has ten cloth sails, like the jib sails of a ship. When the wind freshens, the miller takes in sail by stopping the mill, unhitching one of his sails, winding it around its boom to reduce its exposed area, and tying it fast again.
Whence came the European windmill? Is it an enlargement of Heron's pinwheel? Was it invented in response to a rumor about the windmills of Iran? Nobody knows, although the basic difference of principle between horizontal-shaft and vertical-shaft windmills argues for Heron and against Iran.
Post mills persisted through the High Middle Ages with gradual improvements, such as brakes and means of adjusting the clearance of the millstones. In +XV, however, windmills increased in size in response to the demand for more power. At this time, for instance, the Dutch began to use windmills to drain the many lakes and marshes of their country.
As post mills were enlarged, they became unwieldy, since the whole mill had to turn. They were also likely to be wrecked in gales. So the millwrights developed a mill of another type, called the turret, tower, smock, or cap mill. In the turret mill, the main body of the mill is a fixed, solid structure of wood, brick, or stone. On top of this tower is a revolving turret bearing the sails. The first mill of this kind may have been one built by Leonardo da Vinci at Cesena in 1502. The great Florentine dreamer designed such a mill, though it is not certain that it was actually built. Half a century later, the Dutch were using turret mills for drainage.
With this improvement, mills could be made much larger and more efficient. Millwrights soon were turning out turret windmills that developed as much power as three water wheels, or twenty-five horses, or three hundred men.
There are various ways of turning the turret of a smock mill. In Greek mills of the jib-sail type, the turret is turned by hand. The miller levers it around with a crowbar, which engages pegs on the top of the tower wall and recesses in the turret.
The final refinement in windmill construction was the British invention (-I-XVIII) of the fantail or fly. This was a litde windmill mounted on the rear of the turret, with its sails at right angles to those of the main mill. By means of gearing, the fantail kept the mill facing the wind. This was one of the first self-regulating machines.
