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Windmills: 7th - 15th century

The first practical windmills are constructed in or before the 9th century in a region spanning eastern Iran and western Afghanistan. They are descibed in a manuscript by Estakhri, a Persian georgrapher of that period, as having horizontal sails, like the blades of a helicopter, directly linked by a vertical shaft to the millstones turning below. The date of the first windmill is often given as 644 or earlier, because a 9th-century document says that the man who in that year assassinated the caliph Omar in the mosque at Medina was a Persian builder of windmills. But a first mention of this two centuries after the event makes it unlikely to be true.

Windmills are first mentioned in Europe in the 12th century. There is a reference to one in France in 1180, and a few years later to another in England. Since this is the time of the crusades, it is likely that the idea has been brought from the Middle East.
 








Greek fire: 674

In674 a Muslim fleet enters the Bosphorus to attack Constantinople. It is greeted, and greatly deterred, by a new weapon which can be seen as the precursor of the modern flamethrower. It has never been discovered precisely how the Byzantine chemists achieve the jet of flame for their 'Greek fire'. The secret of such a lethal advantage is jealously guarded.

Contemporary accounts imply that the inflammable substance is petroleum-based, floats on water, and is almost impossible to extinguish. It can be lobbed in a canister. But in its most devastating form it is projected, as a stream of liquid fire, from a tube mounted in the prow of a ship. Sprayed among a wooden fleet, its destructive potential is obvious.
 








Printed Buddhist texts in Korea and Japan: 750-768

The invention of printing is a striking achievement of Buddhists in east Asia. Korea takes the lead. The world's earliest known printed document is a sutra printed on a single sheet of paper in Korea in750.

This is closely followed in Japan by a bold experiment in mass circulation (precisely the area in which printed material has the advantage over manuscript). In768, in devoutly Buddhist Nara, the empress commissions a huge edition of a lucky charm or prayer. It is said that the project takes six years to complete and that the number of copies printed, for distribution to pilgrims, is a million. Many have survived.
 








Gunpowder: 10th century

In about 1040 a Chinese manual on warfare is issued under the title Compendium of Military Technology. It is the first document to describe gunpowder. This black powder, formed by pounding a mixture of saltpetre, charcoal and sulphur (a dangerous process if the pounding is overdone), seems to have been developed in the small chemical laboratories attached to the temples of Daoists where research is conducted mainly on the secret of eternal life.

At this early stage in China the military use of gunpowder is limited to grenades and bombs lobbed at the enemy from catapults. Its real destructive force will only emerge when the explosion is confined, in the development of artillery.
 








Movable type: from the 11th century

Movable type (separate ready-made characters or letters which can be arranged in the correct order for a particular text and then reused) is a necessary step before printing can become an efficient medium for disseminating information.

The concept is experimented with in China as early as the 11th century. But two considerations make the experiment unpractical. One is that the Chinese script has so many characters that type-casting and type-setting become too complex. The other is that the Chinese printers cast their characters in clay and then fire them as pottery, a substance too fragile for the purpose.
 








Compass: 11th century

At some time before 1100 it is discovered that a magnet, if allowed to move freely, will turn so that one end points to the north. Free movement is difficult to achieve, since the natural source of magnetism is a heavy mineral (lodestone or magnetite).

But a fine iron needle can be magnetized by contact with a lodestone, and such a needle is light enough to be attached to a sliver of wood and floated on water. It will then drift into a position which identifies the north - providing invaluable information to seafarers in cloudy weather.
 









There has been much argument about where the compass is first developed. The earliest reference to such a device is in a Chinese manuscript of the late 11th century; within the next 150 years it features also in Arabic and European texts. This is too short a time span to prove the priority of China, given the random nature of the surviving references.

The crucial fact is that this instrument is available to make possible the great age of maritime exploration which begins in the 15th century - though as yet no-one understands why a magnet points to the north.
 






A tower clock in China: 1094

After six years' work, a Buddhist monk by the name of Su Song completes a great tower, some thirty feet high, which is designed to reveal the movement of the stars and the hours of the day. Figures pop out of doors and strike bells to signify the hours.

The power comes from a water wheel occupying the lower part of the tower. Su Song has designed a device which stops the water wheel except for a brief spell, once every quarter of an hour, when the weight of the water (accumulated in vessels on the rim) is sufficient to trip a mechanism. The wheel, lurching forward, drives the machinery of the tower to the next stationary point in a continuing cycle.
 









This device (which in Su Sung's tower must feel like a minor earthquake every time it slams the machinery into action) is an early example of an escapement - a concept essential to mechanical clockwork. In any form of clock based on machinery, power must be delivered to the mechanism in intermittent bursts which can be precisely regulated. The rationing of power is the function of the escapement. The real birth of mechanical clockwork awaits a reliable version, developed in Europe in the 13th century.

Meanwhile Su Sung's tower clock, ready for inspection by the emperor in 1094, is destroyed shortly afterwards by marauding barbarians from the north.
 






Spectacles: from the 13th century

During the 13th century it is discovered that a crystal with a curved surface can help the elderly to read. Mounted in a holder, such a lens is simply a small magnifying glass. The philosopher-scientist Roger Bacon refers to the use of a lens in a text of 1268. At this time it would be shaped and smoothed from a lump of quartz.

Soon (probably in Florence during the 1280s) the idea evolves of placing two lenses in a frame which can be held in front of the eyes. It is a natural next step to perch this frame on the nose. Spectacles, hinged at the centre to grip the nose, appear quite frequently in paintings of the 15th century.
 









As demand increases, glass replaces quartz as the material for lenses and the trade of the lens-grinder becomes one of great skill and importance.

Early spectacles all use convex lenses to redress long sight (difficulty in seeing things which are close). By the 16th century it is discovered that concave lenses will compensate for short sight (difficulty in seeing distant objects). The two everyday forms of spectacle have been achieved.
 






Clockwork in Europe: 13th - 14th century

Europe at the end of the Middle Ages is busy trying to capture time. The underlying aim is as much astronomical (to reflect the movement of the heavenly bodies) as it is to do with the more mundane task of measuring everybody's day. But the attraction of that achievement is recognized too. A textbook on astronomy, written by 'Robert the Englishman' in 1271, says that 'clockmakers are trying to make a wheel which will make one complete revolution' in each day, but that 'they cannot quite perfect their work'.

What prevents them even beginning to perfect their work is the lack of an escapement. But a practical version of this dates from only a few years later.
 









A working escapement is invented in about 1275. The process allows a toothed wheel to turn, one tooth at a time, by successive teeth catching against knobs projecting from an upright rod which oscillates back and forth. The speed of its oscillation is regulated by a horizontal bar (known as a foliot) attached to the top of the rod. The time taken in the foliot's swing can be regulated by moving weights in or out on each arm.

The function of the foliot is the same as that of the pendulum in modern clocks, but it is less efficient in that gravity is not helping it to oscillate. A very heavy weight is needed to power the clock, involving massive machinery and much friction.
 






Artillery: 14th - 16th century

The most significant development in the story of warfare is the use of gunpowder to propel a missile. There has been much debate as to where the first experiments are made. Inconclusive and sometimes mistranslated references from early documents appear to give the priority variously to the Chinese, the Hindus, the Arabs and the Turks.

It is likely that the matter can never be resolved. The earliest incontrovertible evidence of artillery is a drawing of a crude form of cannon in a manuscript dated 1327 (now in the library of Christ Church, Oxford). There is a reference to a gun mounted on a ship in 1336, and the possibility of cannon of some kind in use at Crécy and Calais in 1346-7.
 









The problem confronting early makers of artillery is how to construct a tube strong enough to contain an explosion which will propel a missile out of one end (or, in other words, how to make a gun rather than a bomb). An early solution gives us our word 'barrel'. The tube is built up of metal strips welded to each other along their straight edges - just as a barrel is constructed of similar strips of wood. This rather fragile structure is given greater strength by being encased in a series of tightly fitting metal rings.

With luck, a round stone (or later a ball of cast iron) will hurtle from the open end of this tube when gunpowder is ignited behind it.
 







The laborious loading and firing of such weapons limits their effective use to sieges - either inside a castle defending an entrance, or outside lobbing heavy objects at the walls. The size of the missile rather than its speed is the crucial factor. A breakthrough in this respect, in the late 14th century, is the discovery of how to cast gun barrels from molten iron.

Cannon, during the next two centuries, become progressively larger. There are some impressive surviving examples. Mons Meg, dating from the 15th century and now in Edinburgh castle, could hurl an iron ball, 18 inches in diameter, as far as a mile. The even larger Tsar Cannon in Moscow, cast in 1586 with a bore of 3 feet, weighs nearly 40 tons. Mobility is not one of its features.
 







One of the most remarkable of early cannon is a proud possession of Mehmed, the Turkish conqueror of Constantinople. Before his final attack in 1453 he terrifies the inhabitants by trundling close to their city a massive 19-ton bombard of cast iron. It requires 16 oxen and 200 men to manoeuvre it into its firing position. Once there, it settles down to a slow but devastating bombardment. A stone weighing as much as 600 pounds can be lobbed against the great city walls. The rate of fire is seven stones a day.

In this same same year, at Castillon in France, another potential of gun power is demonstrated - in the effect of light artillery on the battlefield.
 






Hand guns: 14th - 17th century


Portable guns are developed shortly after the first cannons. When first mentioned, in the 1360s, such a gun is like a small version of a cannon. A metal tube, up to a foot long, is attached to the end of a pole about six feet in length - an early and very basic version of the barrel and stock of a rifle.

The gunner has to apply a glowing coal or a red-hot wire to a touchhole in the loaded barrel, and then somehow get far enough away from the explosion. There is clearly not much opportunity for rapid aiming. Most such weapons are probably fired by two men, or are carried to a new position and fixed there before being loaded and ignited by one.
 










Refinements follow surprisingly fast. During the 15th century the barrel of such weapons is lengthened, giving more reliable aim. The wooden stock acquires a curve, so that the recoil raises the barrel rather than driving backwards with full force. A length of rope known as a 'match' replaces the hot coal or wire for igniting the charge in the touchhole; it is soaked in a substance which causes it to burn with a steady glow.

And a device called a 'lock' is developed - a curving arm of metal which holds the glowing match and will plunge it into the touchhole, when a pull on a trigger releases a spring. The 'matchlock' becomes the standard form of musket until the arrival of the flintlock in the 17th century.
 






Type foundry in Korea: c.1230

In the early 13th century, more than 200 years before Gutenberg’s innovation in Europe, the Koreans establish a foundry to cast movable type in bronze. Unlike earlier Chinese experiments with pottery, bronze is sufficiently strong for repeated printing, dismantling and resetting for a new text.

With this technology the Koreans create, in 1377, the world’s earliest known book printed from movable type. Known as Jikji, it is a collection of Buddhist texts compiled as a guide for students. Only the second of the two published volumes survives (held at present in the National Library of France). It reveals not only the date of its printing but even the names of the priests who assisted in the compiling of the type.

The Koreans at this time are using the Chinese script, so they have the problem of an unwieldy number of characters. They solve this in 1443 by inventing their own national alphabet, known as han'gul. By one of the strange coincidences of history this is precisely the decade in which Gutenberg is experimenting with movable type far away in Europe, which has enjoyed the advantage of an alphabet for more than 2000 years.
 








A keyboard for strings: 1397

In a manuscript of 1397 it is reported that a certain Hermann Poll has invented a clavicembalum or harpsichord. In doing so he has adapted the keyboard (long familiar in the organ) to the playing of strings. Whether or not Poll is its actual inventor, the harpsichord rapidly becomes a successful and widespread instrument. It stands at the start of the tradition which will eventually make keyboard music a part of everyday life.

But the harpsichord has one limitation. However hard or softly the player strikes the key, the note sounds the same; the action merely releases a device to pluck the string. For playing soft or loud, a further development is needed - the pianoforte.
 








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