The Ascent of Man (12 page)

Almost ten thousand years ago, not long after the beginning of the settled communities of agriculture, men in the Middle East began to use copper. But the use of metals could not become general until there was found a systematic process for getting them. That is the extraction of metals from their ores, which we now know was begun rather
over seven thousand years ago, about the year 5000
BC
in Persia and Afghanistan. At that time, men put the green stone malachite into the fire in earnest, and from it flowed the red metal, copper – happily, copper is released at a modest temperature. They recognised copper because it is sometimes found in raw lumps on the surface, and in that form it had been hammered and worked for over two thousand
years already.

The New World too worked copper, and smelted it by the time of Christ, but it paused there. Only the Old
World went on to make metal the backbone of civilised life. Suddenly the range of man’s control is increased immensely. He has at his command a material which can be moulded, drawn, hammered, cast; which can be made into a tool, an ornament, a vessel; and which can be thrown
back into the fire and reshaped. It has only one shortcoming: copper is a soft metal. As soon as it is put under strain, stretched in the form of a wire for instance, it visibly begins to yield. That is because, like every metal, pure copper is made up of layers of crystals. And it is the crystal layers, each like a wafer in which the atoms of the metal are laid out in a regular lattice, which slide
over one another until they finally part. When the copper wire begins to neck (that is, develop a weakness), it is not so much that it fails in tension, as that it fails by internal slipping.

Of course the coppersmith did not think like that six thousand years ago. He was faced with a robust problem, which is that copper will not take an edge. For a short time the ascent of man stood poised at
the next step: to make a hard metal with a cutting edge. If that seems a large claim for a technical advance, that is because, as a discovery, the next step is so paradoxical and beautiful.

If we picture the next step in modern terms, what needed to be done was plain enough. We have heard that copper as a pure metal is soft because its crystals have parallel planes which easily slip past one
another. (It can be hardened somewhat by hammering, to break up the large crystals and make them jagged.) We can deduce that if we could build something gritty into the crystals, that would stop the planes from sliding and would make the metal hard. Of course, on the scale of fine structure that I am describing, something gritty must be a different kind of atoms in place of some of the copper atoms
in the crystals. We have to make an alloy whose crystals are more rigid because the atoms in them are not all of the same kind.

That is the modern picture; it is only in the last fifty years that we have come to understand that the special properties of alloys derive from their atomic structure. And yet, by luck or by experiment, the ancient smelters found just this answer: namely, that when
to copper you add an even softer metal, tin, you make an alloy which is harder and more durable than either – bronze. Probably the piece of luck was that tin ores in the Old World are found together with copper ores. The point is that almost any pure material is weak, and many impurities will do to make it stronger. What tin does is not a unique but a general function: to add to the pure material
a kind of atomic grit – points of a different roughness which stick in the crystal lattices and stop them from sliding.

I have been at pains to describe the nature of bronze in scientific terms because it is a marvellous discovery. And it is marvellous also as a revelation of the potential that a new process carries and evokes in those who handle it. The working of bronze reached its finest expression
in China. It had come to China almost certainly from the Middle East, where bronze was discovered about 3800
BC
. The high period of bronze in China is also the beginning of Chinese civilisation as we think of it – the Shang dynasty, before 1500
BC
.

The Shang dynasty governed a group of feudal domains in the valley of the Yellow River, and for the first time created some unitary state and culture
in China. In all ways it is a formative time, when ceramics are also developed and writing becomes fixed. (It is the calligraphy, both on the ceramics and the bronze, which is so startling.) The bronzes in the high period were made with an Oriental attention to detail
which is fascinating in itself.

The Chinese made the mould for a bronze casting out of strips shaped round a ceramic core. And
because the strips are still found, we know how the process worked. We can follow the preparation of the basic core, the incising of the pattern, and particularly the inscribed lettering on the strips formed on the core. The strips thus make up an outer ceramic mould which is baked hard to take the hot metal. We can even follow the traditional preparation of the bronze. The proportions of copper
and tin that the Chinese used are fairly exact. Bronze can be made from almost any proportion between, say, five per cent and twenty per cent of tin added to the copper. But the best Shang bronzes are held at fifteen per cent tin, and there the sharpness of the casting is perfect. At that proportion, bronze is almost three times as hard as copper.

The Shang bronzes are ceremonial, divine objects.
They express for China a monumental worship which, in Europe at that same moment, was building Stonehenge. Bronze becomes, from this time onwards, a material for all purposes, the plastic of its age. It has this universal quality wherever it is found, in Europe and in Asia.

But in the climax of the Chinese craftsmanship, the bronze expresses something more. The delight of these Chinese works,
vessels for wine and food – in part playful and in part divine – is that they form an art that grows spontaneously out of its own technical skill. The maker is ruled and directed by the material; in shape and in surface, his design flows from the process. The beauty that he creates, the mastery that he communicates, comes from his own devotion to his craft.

The scientific content of these classical
techniques is clear-cut. With the discovery that fire will smelt metals comes, in time, the more subtle discovery that fire will fuse them together to make an alloy with new properties. That is as true of iron as of copper. Indeed, the parallel between the metals holds at every stage. Iron also was first used in its natural form; raw iron arrives on the surface of the earth in meteorites, and
for that reason its Sumerian name is ‘metal from heaven’. When iron ores were smelted later, the metal was recognised because it had already been used. The Indians in North America used meteoric iron, but never could smelt the ores.

Because it is much more difficult to extract from its ores than copper, smelted iron is, of course, a much later discovery. The first positive evidence for its practical
use is probably a piece of a tool that has got stuck in one of the pyramids; that gives it a date before 2500
BC
. But the wide use of iron was really initiated by the Hittites near the Black Sea around 1500
BC
– just the time of the finest bronze in China, the time of Stonehenge.

And as copper comes of age in its alloy, bronze, so iron comes of age in its alloy, steel. Within five hundred years,
by 1000
BC
, steel is being made in India, and the exquisite properties of different kinds of steel come to be known. Nevertheless, steel remained a special and in some ways a rare material for limited use until quite recent times. As late as two hundred years ago, the steel industry of Sheffield was still small and backward, and the quaker Benjamin Huntsman, wanting to make a precision watch-spring,
had to turn metallurgist and discover how to make the steel for it himself.

Since I have turned to the Far East to look at the perfection of bronze, I will take an Oriental example also of the techniques that produce the special properties of steel. They reach their climax, for me, in the making of the Japanese sword, which has been going on in one way or another since
AD
800. The making of the
sword, like all ancient metallurgy, is surrounded with ritual, and that is for a clear reason. When you have no written language, when you have nothing that can be called a chemical formula, then you must have a precise ceremonial which fixes the sequence of operations so that they are exact and memorable.

So there is a kind of laying on of hands, an apostolic succession, by which one generation
blesses and gives to the next the materials, blesses the fire, and blesses the swordmaker. The man who was making this sword holds the title of a ‘Living Cultural Monument’, formally awarded to the leading masters of ancient arts by the Japanese government. His name is Getsu. And in a formal sense, he is a direct descendant in his craft of the swordmaker Masamune, who perfected the process in
the thirteenth century – to repel the Mongols. Or so tradition has it; certainly the Mongols at that time repeatedly tried to invade Japan from China, under the command of the grandson of Genghis Khan, the famous Kublai Khan.

Iron is a later discovery than copper because at every stage it needs more heat – in smelting, working and, naturally, in processing its alloy, steel. (The melting point
of iron is about 1500ºC, almost 500ºC higher than that of copper.) Both in heat treatment and in its response to added elements, steel is a material infinitely more sensitive than bronze. In it, iron is alloyed with a tiny percentage of carbon, less than one per cent usually, and variations in that dictate the underlying properties of the steel.

The process of making the sword reflects the delicate
control of carbon and of heat treatment by which a steel object is made to fit its function perfectly. Even the steel billet is not simple, because a sword must combine two different and incompatible properties of materials. It must be flexible, and yet it must be hard. Those are not properties which can be built into the same material unless it consists of layers. In order to achieve that,
the steel billet is cut, and then doubled over again and again so as to make a multitude of inner surfaces. The sword that Getsu makes requires him to double the billet fifteen times. This means that the number of layers of steel will be 2
¹⁵
, which is well over thirty thousand layers. Each layer must be bound to the next, which has a different property. It is as if he were trying to combine the
flexibility of rubber with the hardness of glass. And the sword, essentially, is an immense sandwich of these two properties.

At the last stage, the sword is prepared by being covered with clay to different thicknesses, so that when it is heated and plunged into water it will cool at different rates. The temperature of the steel for this final moment has to be judged precisely, and in a civilisation
in which that is not done by measurement, ‘it is the practice to watch the sword being heated until it glows to the colour of the morning sun’. In fairness to the swordmaker, I ought to say that such colour cues were also traditional in steelmaking in Europe: as late as the eighteenth century, the right stage at which to temper steel was when it glowed straw-yellow, or purple, or blue, according
to the different use for which it was intended.

The climax, not so much of drama as of chemistry, is the quenching, which hardens the sword and fixes the different properties within it. Different crystal shapes and sizes are produced by the different rates of cooling: large, smooth crystals at the flexible core of the sword, and small jagged crystals at the cutting edge. The two properties of
rubber and glass are finally fused in the finished sword. They reveal themselves in its surface appearance – a sheen of shot-silk by which the Japanese set high store. But the test of the sword, the test of a technical practice, the test of a scientific theory, is ‘Does it work?’ Can it cut the human body in the formal ways that ritual lays down? The traditional cuts are mapped as carefully as the
cuts of beef on a diagram in a cookery book: ‘Cut number two – the O-jo-dan.’ The body is simulated by packed straw, nowadays. But in the past a new sword was tested more literally, by using it to execute a prisoner.

The sword is the weapon of the Samurai. By it they survived endless civil wars that divided Japan from the twelfth century on. Everything about them is fine metalwork: the flexible
armour made of steel strips, the horse trappings, the stirrups. And yet the Samurai did not know how to make any of these things themselves. Like the horsemen in other cultures they lived by force, and depended even for their weapons on the skill of villagers whom they alternately protected and robbed. In the long run, the Samurai became a set of paid mercenaries who sold their services for gold.

Our understanding of how the material world is put together from its elements derives from two sources. One, that I have traced, is the development of techniques for making and alloying useful metals. The other is alchemy, and it has a different character. It is small in scale, is not directed to daily uses, and contains a substantial body of speculative theory. For reasons which are oblique but
not accidental, alchemy was much occupied with another metal, gold, which is virtually useless. Yet gold has so fascinated human societies that I should be perverse if I did not try to isolate the properties that gave it its symbolic power.

Gold is the universal prize in all countries, in all cultures, in all ages. A representative collection of gold artefacts reads like a chronicle of civilisations.
Enamelled gold rosary, 16th century, English. Gold serpent brooch, 400
BC
, Greek. Triple gold crown of Abuna, 17th century, Abyssinian. Gold snake bracelet, ancient Roman. Ritual vessels of Achaemenid gold, 6th century
BC
, Persian. Drinking bowl of Malik gold, 8th century
BC
, Persian. Bulls’ heads in gold … Ceremonial gold knife, Chimu, Pre-Inca, Peruvian, 9th century …

Sculpted gold salt-cellar,
Benvenuto Cellini, 16th-century figures, made for King Francis I. Cellini recalled what his French patron said of it: