Works of Man

By Ronald Clark

Works of Man is a chronicle of man's attempts from prehistoric times to the space age to exploit for his own purposes the slowly discerned laws of nature. Exciting, instructive, and eminently readable, this mine of information covers the broad sweep of technological achievements, from the invention of the wheel more than six millennia ago to the miniaturization of the electronic computer.

Beginning with a description of the early builders in the days of ancient Babylon, continuing through to the end of the Roman Empire, the author goes on to explain the engineering principles that were gradually developed in the Dark Ages, enabling men to build the medieval cathedrals; to try to drain the Pontine marshes near Rome, the meres of Holland, and the British fenlands; and to raise the new military defenses that transformed warfare. Discussion of the work of Leonardo da Vinci and Galileo leads on to the development of steam as a new source of power, and to the growth of civil engineering that followed in Europe and the rest of the world. Further chapters cover the change from sail to steam; canals; railways; the use of electricity; the growth of manned flight; the rise of the plastics industry; nuclear engineering; and the problems of space exploration.

• Language: English
• Publisher: Bloomsbury Publishing
• Release date: Oct 28, 2011
• ISBN: 9781448206216

Ronald Clark

Ronald Clark was born in London in 1916 and educated at King's College School. In 1933 he chose journalism as a career; during the Second World War, after being turned down for military duty on medical grounds, he served as a war correspondent. During this time Clark landed on Juno Beach with the Canadians on D-Day and followed the war until its end, then remained in Germany to report on the major War Crimes trials. Clark returned to Britain in 1948 and wrote extensively on subjects ranging from mountain climbing to the atomic bomb, Balmoral Castle to world explorers. He also wrote a number of biographies on a myriad of figures, such as Charles Darwin, Thomas Edison, Albert Einstein, Benjamin Franklin, Sigmund Freud, and Bertrand Russell. Clark died in 1987.

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Introduction

Many factors have contributed through the centuries to the stumble forward of progress which has enabled men to exploit the laws of nature by using ever more complex buildings and machines. Not the least has been chance, that arbiter which, as Winston Churchill once said, can govern which side of a tree an officer steps and thus settle whether he ends up a mangled wreck or survives as a successful commander.

Yet, if there is one component on which most if not all technological progress rests, it is probably that described by the late A.P.Rowe, director of Britain’s Telecommunications Research Establishment whose ability to keep its wartime staff of radio geniuses and prima donnas working as a team played a significant part in winning the war. The birth of radar, he once wrote, ‘awaited contact between those with a need and those with a contact which would meet that need’ — in this case contact between H.E.Wimperis, director of scientific research at the Air Ministry, and Robert Watson-Watt of the Radio Research Station, working at the time on a radio technique without thought of military application. At least as far back as 1921, Marconi had noted that the position of ships could be pinpointed by their reflection of radio waves. Edward Appleton, probing the layers of the ionosphere a few years later, had reported similar phenomena. Both naval and Army research workers had speculated on the possibilities of radio-location in the later 1920s. Yet it was only after the 1934 Air Exercises had shown that London was wide open to attack from the air, that radar was pulled into existence as a possible way of meeting the danger.

An urgent need of this kind has invariably been required before a potential technological advance has been changed from dream to reality. Thus the steam-driven caterpillar-tracked vehicle which was actually built in 1888 was forgotten until the machine guns of World War I made development of the tank or its equivalent a necessity.

A need leading to its satisfaction — sometimes by circuitous routes — can be seen clearly enough in many of the chapters, from prehistoric times to the space age, which chronicle man’s attempts to change his environment, improve his living conditions, and generally exploit for his own purposes the slowly discerned laws of nature. It is nowhere more obvious than in the story of the revolutions produced by the steam engine, a story which runs as an unbroken thread through so much of historic times. It was the imminent exhaustion of Britain’s forests, their timber needed for building the ‘wooden walls’ of the Royal Navy, which provided the initial spur. As wood became in ever shorter supply, even for ship-building, it was replaced as fuel by the coal which lay in abundance below so much of Britain’s countryside. But miners were often faced by one crippling problem: seepage of water into the mine-workings. First hand-pumps were used to drain the water, then pumps operated by animals. But as coal was mined at ever greater depths, something more efficient was required. The experiments which had been carried out on the Continent as the philosophers of the Renaissance world encouraged scientific thought, were conscripted and developed by a succession of Englishmen and Scotsmen for utilitarian purposes and the steam engine came into existence to help keep coalmining alive.

Once the steam age had shown that coal pits could apparently be kept open indefinitely, the distribution of coal throughout a country where communications were little better than those of Roman times demanded two developments: the growth of canals and, once it was shown that steam could provide mobile motive power, the great age of the railways. Simultaneously, the Industrial Revolution was made possible by whole families of ingenious steam-driven machines — not only railway engines and engines to power ocean liners, but the varied equipment that during the nineteenth century made Britain ‘the workshop of the world’. The example was followed, elsewhere in Europe and in the United States, more quickly than was expected.

This spread of engineering was made possible by scientific investigation of the materials used and, a natural development, the production of more efficient metals. By the end of the eighteenth century science had provided the base on which the builders of the early steam engines had been able to improve the efficiency of the machinery they made. Then, in the nineteenth century, science made it possible to use safely new materials and new methods in structures as remarkable as London’s Crystal Palace, the Eiffel Tower of Paris, and the Forth Bridge, that wonder of the late Victorian age. Here, as could be shown from the prehistoric Iron Age onwards, science and technology moved forward together, spurred on either by political or economic need — both in the case of the Forth Bridge — or, as with the Crystal Palace and the Eiffel Tower, by the genius of an imaginative engineer. Little wonder that before the century was out men working at the sharp end of scientific invention would be creating metals, plastic materials and artificial dyes tailor-made to carry out specific tasks.

At the end of the nineteenth century, development of the petrol engine at last solved the power-to-weight problem of men who wished to fly. Thirty years later the production of metals capable of withstanding temperatures of a new ferocity enabled Frank Whittle decisively to change the air maps of the world with his jet engine. Not long afterwards, and in the wake of the electronic revolution which was a direct outcome of World War II, fear of what the Russians might achieve drove the Americans into the technological successes of the space age with its multiple spin-offs for everyday life. It is ironic that a decade earlier fear of what the Germans might achieve had driven the rest of the world into the nuclear revolution whose transformations of life are not yet complete after four decades.

The works of man which have been changing the face of the planet since prehistoric times can thus be seen as responses to needs which have eventually been satisfied by human thought and ingenuity. These responses have themselves sprung from the ambitions and quiddities of men who have spied a need either by good luck or due to an underlying and useful genetic make-up. But they have invariably had to press on with their work in the face of the setbacks that dog all pioneers. Progress, when all is said and done, usually reveals itself as a matter of character as well as of luck.

Big Buildings of the Ancient World

The first engineer was the man who looked at the two upright stones before his cave, believed they would support the weight of a horizontal lintel, and contrived to raise into position a third stone which made the structure safe and sound.

This innovator could also be considered an architect, since in ancient times the architect was the engineer in embryo, and for millennia the duties of each tended to overlap. In due course the control of water, the exploitation first of metals, then of steam, produced a family of specialist engineers, later divided and sub-divided into men who dealt with military and civilian applications of the natural laws; into chemical, electrical and aeronautical engineers and then into the experts of modern times, each creating his own variety of man-made wonders.

But before even the first engineering achievements could come into being, man had to make certain elementary advances on which the interconnected disciplines of engineering, science and technology were to depend. The marvels of the pyramids and of the space shuttle, of the Roman Colosseum and the multi-thousand ton concrete foundations of a nuclear power station laid correct to a ten-thousandth of an inch, all follow fundamental discoveries without which engineering would never have existed.

The first crucial step forward — or, more accurately, succession of steps — was control of fire, needed as a protection against cold and wild animals, then used to make raw food more palatable. Eventually, and after how many thousands of years is unknown, early man discovered that fire could perform two other allied functions. One was to produce metals such as iron from the metallic ore lying in the ground. The other was the heating of different metals until they melted and the production, by mixing them, of alloys which were harder than their separate components. From copper and tin it was possible to produce bronze. Moreover by increasing the tin content bronze could be made harder; by decreasing it the alloy was made more malleable. Thus it became possible to produce materials tailor-made for special purposes.

Next came the wheel. Potters’ wheels are known to have been in existence at least 6,000 years ago and it is possible that wheeled transport began equally far back. However, the earliest examples were of wood and are unlikely to have survived. The date when wheels revolving on axles began to take over from the long sleds which were for centuries the only means, other than beasts of burden, for moving heavy loads, remains unknown. Certainly by 2500 BC chariot wheels were used in the Sumerian armies of Mesopotamia. The first wheels, introduced about 4000 BC, were solid. Spoked wheels gradually replaced them and were in fairly common use by about 2000 BC. During the transitional period openings in the solid wheels became spokes, the process continuing in both agricultural vehicles and war chariots.

At some equally unknown but certainly distant date man began to develop the use of iron, the fourth in quantity of the elements found in the crust of the earth, but one which has been chemically understood only in the last three hundred years. Iron exists in nature as various ores whose components can be separated by heat and it is likely that the first ‘smelting’ of iron occurred by accident in a camp fire which, on going out, was found to contain a spongy mass, a ‘bloom’, of iron in a mixture of slag and cinders. Frequent reheating and hammering produced what was to become known as wrought iron. Later it was discovered that quenching in cold water made it harder than bronze.

These basic steps had been taken at least by 3000 BC, the date by which primitive man began to evolve from a food gatherer into a food producer. The transformation meant that he started to live in permanent quarters throughout the year, instead of being constantly on the trot as he followed the animals who moved with the seasons. With settlement, and a growing dependence on crops, there came an increased need for river control and irrigation. These were in most cases two sides of the same coin. But it is in the development of irrigation in Mesopotamia and Egypt — as well as in the Indus Valley of India and the Yellow River Valley of China — that primitive engineers made their first, and essential, contributions to the spread of civilization. Without distribution of the waters which allowed men to grow crops each year, populations would have remained small, towns and cities would have failed to develop and life itself would have been altogether more precarious in an environment where water is the first requirement for survival.

The problems of water control which faced the early engineers were different around the settlements of Mesopotamia, strung out along the Tigris and the Euphrates, from those in Egypt where life was dependent on the Nile. The waters of the Tigris and the Euphrates rose at some unpredictable date between April and June, and could bring enough silt to clog irrigation channels. The water had, therefore, to be carefully controlled and then stored for use in the months when it could best be distributed. By comparison, the Nile rose more predictably, less fiercely and at a more convenient time, so that its waters could be led direct into a network of irrigation channels. But its annual inundations were so great that property boundaries had to be regularly redelineated, a requirement that led to the art of surveying.

It is only of the more spectacular irrigation schemes of ancient times that anything is known today. But throughout thousands of square miles in the great river valleys where the earliest civilizations flourished, a wide variety of such schemes were dug during the millennia before Christ. Some supplied surface irrigation by means of a network of furrows criss-crossing the land. Others provided subsoil irrigation and consisted of deep channels dug round the entire plot and kept filled with water which gradually but continually seeped into the surrounding ground.

Some schemes were remarkably ambitious. Nebuchadnezzar in the eleventh century BC drained the Nahmalka, an arm of the Euphrates, and built above the city of Sippara a reservoir 20 fathoms (36 metres) deep from which waters could be let out to irrigate the surrounding plain. Three hundred years later King Assuranzairoak of Assyria cut a mile-long channel through the rock at Negoub as part of a scheme to divert the waters of Zab to Numrud. And in the seventh century BC King Sennacherib built the astonishing stone canal which brought water to Nineveh from Bavia, some 50 miles (80 kilometres) away. Sennacherib banked in the Tigris, built a great temple at Nineveh and carried out a big programme of public works. But his most important achievement was the 50 mile (80 kilometre) canal, lined with more than two million blocks of stone. At one place, where it was 20 yards (18.3 metres) in width, it crossed a 300 yard (274 metre) wide river on an aqueduct supported by five arches, while outside Nineveh a complex system of dams and sluices enabled it to irrigate the surrounding country. The waterproofing of the canal was extremely sophisticated, consisting of a bed of concrete which was floated on bitumen, and on which there was laid a stone pavement, accurately jointed and sloped to a fall of one in 80. The grading of the canal was made with greater accuracy than was necessary for ensuring an unbroken supply of water and appears to have been planned so that as one section was completed the blocks for the next section could be moved down the watercourse on rollers.

Ancient Egypt had comparable irrigation systems as well as a flood-storage scheme 50 miles (80 kilometres) south of Cairo where the marshy Faiyum depression could be filled and its waters fed into the Nile by the Canal of Joseph, often considered the oldest canal in the world. There were also at least two stone and masonry dams south of Cairo, built about 3000 BC and throughout most of Egypt’s history the waters of the Nile were controlled with considerable success.

With few exceptions, irrigation demanded the raising of water from one level to another and in the ancient world manpower, animal power, water power were all used, and sometimes an ingenious combination of all three. The most simple device was the shaduf, an apparatus consisting of a bucket at the end of a counterweighted lever; the operator pressed the bucket into the lower water level, then allowed the counterweight to raise it, after which the water was tipped out into the higher level. There was also the Archimedean screw, a hollow helical cylinder which acted as pump if rotated while one end was submerged below water. Of the various animal-powered methods, one of the most used was the saquiyah in which an endless chain of pots was dropped into a well, and pulled from it, by an animal walking constantly in a circle to keep the chain moving. Among the water-powered methods were the tympanum and the noria. The first was a drum with eight compartments turned treadmill fashion on a horizontal axis so that its lower sections dipped into a stream. Each of the eight compartments in turn scooped up water which was enabled to flow out through holes in the drum into a wooden trough. The noria consisted of a series of bottles, attached to the circumference of a horizontally mounted wheel which dipped into a stream; this kept the succession of bottles constantly on the move, and thus deposited their contents into a trough whence the water was led to where it was needed.

The waters of Mesopotamian rivers and of the Nile not only enabled early man to grow crops but also provided him with one of his most important sources of power. This was probably first used for milling grain, and three kinds of water mill are known from ancient times. The first was almost certainly the vertical shaft mill which consisted of a number of wooden blades, inclined at about 30 degrees to the vertical and attached to a hub which was fixed near the bottom of a vertical shaft. It was necessary for the water, directed on to the blades by a wooden trough, to fall a certain minimum height on to the blades so that the ‘used’ water could flow away easily. This meant that a pit had sometimes to be dug to ensure the most efficient operation of such mills.

Two other varieties of water mill eventually superseded this primitive kind; the undershot mill, often called the ‘Vitruvian’ because of its detailed description by the Roman author and architect Marcus Vitruvius Pollio, and the overshot mill which was the most efficient of all. The undershot mill was simply a wheel on a horizontal axle, its circumference bearing vanes or paddles and its lower portion dipping into the moving stream which turned the wheel on its axle. The wheel of the overshot mill was also horizontally mounted, but in this case it was mounted clear of the water while its circumference carried a number of buckets or similar containers. The water from a stream was led on to the top of the wheel where it filled a succession of the buckets; their weight turned the wheel as gravity emptied the buckets and the continuing flow of water filled their successors. Such simple constructions, to which were later added toothed wooden gears enabling horizontal motion to be turned into vertical motion, or vice versa, appear from very early times. Later versions remained in use in western Europe until steam power began to take over from water power in the eighteenth century.

Construction of the early irrigation schemes demanded of their planners, usually priests, little more than rudimentary knowledge, attained by a process of trial and error, which taught them how high and wide enclosing banks should be, and how wide and deep water channels should be to do certain specific jobs. The main difference between the early engineering works in Egypt and those to the east in Mesopotamia was the greater availability of stone in Egypt.

The contrast is shown in their public buildings. In both areas the humble houses of ordinary people were built of sunbaked bricks, but religious buildings were of something more substantial. In Mesopotamia the structure was the ziggurat, usually constructed of brick and rising in a series of rectangular terraces often adorned with plants and flowers. The most famous was the Hanging Gardens of Babylon, covering four acres, based on masonry arches, and with its plants and trees irrigated from a reservoir on top of the ziggurat which was kept perpetually filled with water from the Euphrates. Similar buildings were sometimes of considerable sophistication as well as size. Ur-Nammu’s ziggurat at Ur was 79 yards (72 metres) by 59 yards (54 metres) and 28.6 yards (26 metres) high. The façades, made of kiln-dried brick set in bitumen, leant inwards to give an appearance of strength while horizontally they were built with a deliberate convexity to correct the illusion of perspective. To counter the danger of uneven settlement, reeds were used as binding material. At places even more care was taken by the engineers and in a ziggurat at Aqar Quf every fifth course of brickwork was interrupted by a layer of reed matting. The whole structure, moreover, was criss-crossed by cables of tough reeds laid in alternate directions.

In Egypt there were the pyramids, its surviving examples among the most impressive of the early engineers’ work to be seen. They were the result, as one scholar has said, of ‘the desire for eternal life’, and each contained a chamber or chambers in which one or more members of the ruling family would be laid after death. Vast efforts were put into these monuments and Jean François Champollion, one of the founders of modern Egyptology, remarked in the nineteenth century: ‘No people, either ancient or modern, have had a national architecture at once so sublime in scale, so grand in expression, and so free from littleness, as that of the ancient Egyptians.’ The lid of one sarcophagus, a coffin to be placed in a pyramid, needed 3,000 men for its transport.

The pharaohs of ancient Egypt are today usually grouped into thirty-one dynasties, running from 3188 BC to 332 BC and most of the eighty pyramids, or remains of pyramids which have been identified by archaeologists were built in the third or fourth dynasties, grouped together as the Old Kingdom, between 2815 BC and 2294 BC. During these five hundred years design and method naturally changed although most of the pyramids — including those that were built before and after the main centuries of construction — had certain features in common. All were built from huge blocks of stone whose movement and assembly presented great problems in the days before the use of scaffolding or of block and tackle. Exactly how the builders overcame their difficulties is still open to discussion, and although writing was developed, first by the Sumerians in the barren lands of Mesopotamia, as early as 3000 BC, most of what is known about construction of the pyramids comes from archaeological evidence slowly accumulated over the years.

The pyramid builders, it is now known, understood the use of the wedge and the lever. They used copper tools such as chisels to cut limestone and wooden wedges to split granite blocks from the quarries. The balance beam weighed quantities with considerable accuracy and, perhaps more important, rollers and sledges were employed to move heavy loads. This method was used by other early builders. The great Assyrian winged bulls of Khorsabad, weighing more than 19.6 tons, were first rough-hewn in the quarry, moved by water, then completed their journey by sled, and were moved into position with the help of rollers, ropes, levers and pulleys, before being finished on site. A 60 ton alabaster statue of Dhutotpe was moved on rollers from its quarry to the Nile by 172 men, some of whom poured oil or water on the rollers to lessen friction.

After it had been decided to build a pyramid, the first task was to choose a suitable site. It had to be close enough to the Nile to make movement of stone from the river to the site not too difficult; but it could not be so close that there was risk of inundation during the flood season. The site had to be accessible either from the country’s contemporary capital or at least from one of the king’s residences. The substratum of rock had to be capable of bearing very heavy weights and the ground not too difficult to level.

Once the site had been decided, levelling was carried out — and in the case of the Great Pyramid of Gizeh this appears to have been accurate to within half an inch. The base of the pyramid was then surveyed, care being taken to ensure that the four corners pointed to the cardinal points of the compass. That done, the way would be ready for three operations that were frequently performed simultaneously. One was the construction of a causeway from the Nile to the building site up which the materials would eventually be hauled. The second was quarrying the local limestone for the outer casing of the pyramid, much of it found on the east bank of the river at Tura in the Mukattam hills. At the same time, the granite to be used in the building would be quarried near Aswan, some 300 miles (483 kilometres) upstream.

Quite apart from the organization needed to bring thousands of men to the site at the right time, there also had to be planning to ensure that separate operations could be tied in with each other to complete the job.

Much of the quarrying was followed by rough-hewing on the site. For this there was available the hafted hammer, an instrument which gave access to more power than man had previously had under control. Yet however much ‘waste’ was removed in the quarry the builders still had the enormous problem of moving the massive blocks of stone.

The most famous of the gigantic structures which they built with primitive equipment was the Great Pyramid of Gizeh, a few miles south-west of Cairo, constructed about 2600 BC to provide a funeral monument for King Cheops (also known as King Khufu). Rising to a height of about 463 feet (141 metres) from its square 779 feet (237 metres) base, it contains about 2,300,000 2½-ton blocks of limestone, the inner ones being of rough stone, the outer ones of fine limestone fitted together with great accuracy. Inside the structure, the chambers are lined with granite blocks from Aswan.

As surprising as the builders’ ability to move such immense quantities of material is the precision with which the structure as a whole was built. The base lines are only 7 inches (17.78 centimetres) out of true while the four corners are only of a degree off the four cardinal points of the compass on which they are oriented.

The Greek historian Herodotus gave the earliest account of how the blocks were moved from the Nile along a stone causeway after they had been floated downstream on huge rafts from the quarries from which they had been hewn. ‘It took ten years’ oppression of the people to make the causeway for the conveyance of the stones, a work not much inferior in my judgment to the pyramid itself,’ he wrote. ‘The causeway is five furlongs long, ten fathoms wide, and in height at the highest part, eight fathoms. It is built of polished stone and covered with carvings of animals.’ Once this approach road from the Nile to the building site had been finished, another twenty years is thought to have been needed for building the pyramid itself, and a total of 100,000 men are said to have been required for the work.

The huge blocks were apparently brought from the quarries with their vertical and horizontal joints already prepared and their edges squared. They were then hauled from the river’s edge to the site with the help of rollers and sledges and manhandled into position. When one course, or layer, was finished, an earth ramp was built to its upper level and the stone blocks for the next course were hauled up it into position. There was no pulley or tackle but the task of the steadily hauling humans was eased by the use of viscid mortar on which each successive layer was ‘floated’ into position.

Considerable use was also made of ‘rockers’, designed somewhat like the homely rocking chair. The rocker was tilted and then held in position by logs while the stone to be moved was slid on to it. Movement of the logs, or of others placed at the opposite end of the apparatus, put the stone where it was wanted. The process of raising first one end of the rocker, and then the other, could lift stones as required. Mortar was rarely used, except to help move the large blocks into position after which dowels of sycamore wood or sometimes of iron, helped hold them in place.

Within the Great Pyramid of Gizeh there are three funeral chambers. The first, below ground level, was hewn out of the solid rock on which the pyramid was to be built and was reached by a descending passage. The second, the Queen’s Chamber, was positioned below the apex of the pyramid and reached by an ascending passageway. Finally, there was the King’s Chamber, built roughly at the centre of the structure and connected by a passageway with the Queen’s Chamber almost immediately beneath it.

The accurate siting of the sides of the Great Pyramid to north, east, south and west is proof that its builders had at least an elementary knowledge of astronomy, since they had no magnetic compass. However, there is no foundation for any of the mystical theories which have been devised to explain the situation or the size of any of the pyramids. Such theories were sometimes taken to extreme lengths and the famous Egyptologist, Sir William Flinders Petrie, once recalled how he had met a man measuring one side of the Great Pyramid, but armed with a chisel as well as a tape measure. On asking about the need for the chisel, Petrie was told it was to ‘adjust’ the length of the side that did not conform to the latest theory.

The Egyptian rulers, as well as their engineers, took their pyramids seriously, and in the time of Rameses the Great, during the third millennium BC, an expedition to secure material for one pyramid involved the assembling of nearly 9,000 men. Five thousand were soldiers, 2,000 were temple staff and the balance included 800 foreign auxiliaries, 900 officials, 130 quarrymen and stone-dressers, three master quarrymen and four sculptors.

The facilities which such armies of workmen had at their disposal were non-existent in some spheres, very good in others. Mechanical equipment was of the most elementary sort, and, while thousands of men were available for moving massive quantities and weights, organization must have been stretched to its limits. Yet the Egyptians produced amazing results. Petrie has pointed out that the granite sarcophagus of Senusert II of 3350 BC was ‘ground flat on the sides with a matt face like ground glass that only has about a 200th of an inch error of flatness and parallelism of the side’.

The propensity of the Egyptians, and of the Babylonians and Assyrians too, for building massive monuments was not unique. In fact, throughout most of the ancient world, a high percentage of the available engineering-cum-architectural resources was devoted to the construction of buildings raised for semi-religious reasons or as genuine temples. This concentration of activity was not surprising since many of the works automatically connected with engineering in contemporary life had not yet come into existence. Machinery, in the modern meaning of the word, did not yet exist. The chariot was the most complicated piece of transport mechanism that had yet been devised while the ship, whether pulled through the water by human rowers or using the wind on its sails, was comparatively simple. The equivalent of engineering expertise went into the construction of massive stone buildings and this was true not only of the Middle East and the Far East, but also of Europe where the builders of the Bronze Age erected a number of monuments that are still, thousands of years later, among the most impressive works that man has created. Among them are the thousand shaped granite monoliths arranged in complex stone alignments at Carnac, in south-west France, and the unique group of monuments still standing on Salisbury Plain in the south of England.

The most famous of the British monuments is Stonehenge, 8 miles (12.5 kilometres) from the city of Salisbury and the greatest prehistoric temple of its kind in the world. A few miles away there is Avebury, described by John Aubrey in the seventeenth century as surpassing Stonehenge as much as a cathedral surpasses a village church. Between these two centrepieces is a countryside almost littered with the long barrows in which prehistoric people buried their dead, remains of sanctuaries and of other relics from an age when this chalk upland was the main ‘metropolis’ of England. A geological map shows how the comparatively high chalk ridge running from East Anglia to the south coast in Dorset meets those of the North Downs and the South Downs in the area of Salisbury Plain. These chalk ridges, together with other high ground, provided the highroads of prehistoric times, useable in bad weather as well as good, and it is inevitable that prehistoric man should have left some of his most impressive monuments along them.

The first sight of Stonehenge genuinely merits the term awe-inspiring, — concentric circles of standing stones, gigantic in size and obviously enormous in weight, many of them approaching 50 tons, and some of them capped by horizontal lintels and thus forming what are known as trilithons.

The history of Stonehenge is a complicated one. Surrounding the circles are the remains of an earlier bank and ditch, built about 2800 BC — some time before the Great Pyramid. Inside the bank, small circles of bare chalk mark the position of a ring of fifty-six pits, known as the Aubrey Holes after their discoverer John Aubrey, and apparently dug when the bank was raised.

The first Stonehenge could boast of only three stones — the Heel Stone standing some way outside the bank, and two smaller stones beside it. Five centuries or so later, eighty bluestones, each weighing up to 4 tons, were brought to Stonehenge from the Prescelly Mountains in South Wales — the only place in Britain where this stone is found — and set up to form a double circle inside the ditch. At the same time an approach in the form of the Avenue was made from the nearby River Avon by an earthwork avenue no longer in existence. About a century later the double circle of bluestones was dismantled and the stones replaced by about eighty sarsens, some of them weighing as much as 50 tons. The sarsens — sandstone boulders lying on the Marlborough Downs 20 miles (32 kilometres) north of Stonehenge — were arranged as a circle of uprights capped by a continuous stone lintel, and as a horseshoe of stones within the circle. Possibly as part of the same plan, about twenty of the discarded bluestones were later erected as an oval. This in turn was soon demolished and the bluestones re-erected in a fresh circle. The axis of the final rearrangement points in one direction to the midsummer sunrise and in the other to the midwinter sunset. It follows the line of its predecessor and may have originated even earlier.

Impressive as is Stonehenge today, the sarsens and bluestones still standing are only the remnants of the five successive building operations that went on between 2800 BC and 1550 BC. There is no building stone in the area and for centuries both sarsens and bluestones were broken up for use in farms or to repair farm tracks. Visitors also damaged the monument and for some while it was possible to hire in the nearby small town of Amesbury a hammer suited to chipping off parts of the stones.

Of the engineering riddles raised by Stonehenge, the most difficult to answer was for long the problem of how the bluestones were brought to Salisbury Plain from the Prescelly Mountains, about 240 miles (384 kilometres) away and on the far side of the River Severn and the Bristol Channel. But in 1954 archaeologists conjectured that it would have been possible to move the bluestones by water down to Milford Haven on the Bristol Channel, up the Severn to its junction with the River Avon and then up that river to within a few miles of Stonehenge, whence they could be dragged on sledges. The theory was tested by an elaborate experiment. A dummy bluestone, made of concrete but of correct size and weight, was loaded on to three replicas of prehistoric dugout canoes lashed together. The craft was successfully poled down and up the watercourses to a landing point on the Avon, the only implements used being those available in prehistoric times. Finally a sledge on rollers was brought in to help manhandle the load to Stonehenge. Shortly afterwards similar rollers were used to move the equivalent of 50-ton sarsens from their original site on the Marlborough Downs.

Construction of the trilithons at Stonehenge had also presented engineering riddles, but experiments now suggested that it could have been carried out by first moving an upright on rollers until what was to be its bottom end hung over a previously dug pit. The upright was then dragged by ropes until the lower end dropped into the pit, after which it was raised vertically by further ropework. After a second upright had been raised in the same way the horizontal lintel was first rollered into position and then raised, a few feet at a time, by being levered on to a wooden platform that was progressively raised in height until it reached the top of the vertical sarsens. Further ropework then moved it into its final position.

Three features of Stonehenge’s trilithons reveal that the engineers who planned their erection had more knowledge and skill than is at first apparent. Thus the uprights have been finished — with only the primitive tools of the day — so that they are wider at the top than at the bottom; the result is that the effects of foreshortening are removed when the uprights are viewed from the ground. In addition, none of the horizontal lintels is quite straight; instead, they are curved lengthwise so that they fit the curve of the completed circle. A greater demonstration of the early builders’ skill is given by the hollowed-out mortises at each end of the lintels and the 9 inch (23 centimetre) tenons on the uprights which fit into the mortise holes.

To the north of Stonehenge, near Silbury Hill, the largest artificial mound in Europe, 130 feet (40 metres) high and covering 5½ acres (2.2 hectares), lies the huge embanked enclosure of Avebury, older and larger than Stonehenge. Greatly impressive, despite the depredations of the last two centuries, the bank and ditch enclose almost 30 acres (12 hectares), and from the top of the bank there is visible the remains of the hundred-sarsen circle inside the ditch and of the two smaller circles within it. Leading from the southern entrance to the site lies what is left of the Avenue, a double line of sarsens leading to what was once the Sanctuary, believed to have been a wooden temple. Only modern markers show where the posts of the Sanctuary once stood.

Built in two bursts of activity between 2600 BC and 2000 BC, Avebury, unlike Stonehenge, contains only undressed stones. But in the circles, as in the Avenue, upright stones often alternate with diamond-shaped sarsens — ‘male’ and ‘female’ stones according to some theories.

The great achievements of the earliest builders, in the Middle East as well as in Britain, were carried out with little help from what would today be considered real engineering knowledge. Most of this became available only slowly, over the centuries, during the rise and fall of Greece. The Parthenon, built on the Acropolis at Athens, was among the most famous examples of Greek architecture. Phidias was the sculptor in charge and under him worked the architects Actinus and Callicrates. The building was completed between 447 BC and 438 BC. In modern times various complicated systems on which the building is claimed to have been erected have been put forward to explain the visual beauty of the result.

The men who are often first thought of as the shining examples of Greek civilization are the philosophers, mathematicians and others who concentrated on theoretical knowledge. They were certainly to help lay the foundation on which engineering was to be built. Yet there were those, some much less well known, who were genuine engineers in their own right. Among them was Eupalinos, sometimes called the first civil engineer. About 530 BC Eupalinos built a water-supply system for his native town of Nagara, but he is more famous for the construction on the island of Samos of an aqueduct that required a tunnel, three-quarters of a mile long, through an intervening hill. The tunnel, of 8 feet (2.44 metres) square cross-section, was started simultaneously from both ends, and the survey work was so good that the two tunnels met only 2 feet (0.6 metres) off true.

Two and a half centuries later Archimedes worked out in mathematical detail the principle of the lever; founded the science of statics that was to be of importance in the Renaissance revolution of the sixteenth century when his works were translated from Greek into Latin; and invented the hollow helical screw known as the Archimedean screw which was to be used as a water pump.

To this period there belongs, also, the Pharos of Alexandria, the huge lighthouse which was sometimes named as one of the seven wonders of the world. Pharos was the name of the island which lay about a mile off the coast and which was joined to the mainland by a causeway three-quarters of a mile long, awash when the Nile was high. Here, about 270 BC, in the reign of Ptolemy II, called Philadelphos, the architect Sostrastos of Cnidos was commissioned to build a tower topped by a warning light that would be as much a symbol of Alexandria’s commercial power as a guidance to seafarers.

The base of the Pharos — a word which as phare in French and faro in Italian and Spanish, eventually became a generic term for lighthouse — was a 24 foot (7.4 metre) high heavy stone platform. On this three sections were erected, respectively square, octagonal and cylindrical, thereby bringing the height of the building to between 300 and 400 feet (91.4 and 122 metres). Ramps and stairs led to the top platform where a bright fire of wood was kept burning at night. The Pharos was by far the tallest tower in existence and its construction was so good that it lasted until the thirteenth century when it was destroyed by an earthquake.

Size alone sometimes put the Pharos among ‘the seven spectacles’, first named by Philon of Byzantium at the turn of the third and second centuries, and it is a tribute to the ancient world’s respect for size alone that the world’s wonders, of which several lists were made, depended so much on this one factor. The works of man which so impressed the ancients were the ‘hanging gardens’ of Babylon; the pyramids; the statue of Zeus executed at Olympia by the Athenian sculptor Phidias; the massive Colossus of Rhodes, a statue of Helios the Sun god whose legs allegedly bestrode the entrance to the harbour; the Temple of Ephesus; the Mausoleum of Halicarnassos; and either the walls of Babylon constructed by Nebuchadnezzar, or the Pharos of Alexandria.

Following Archimedes there came Ktesibios who in the second century BC helped to found the engineering tradition at Alexandria. His most famous work was a reconstruction of the clepsydra, the water clock of the Egyptians. This was a jar of water at whose base there was a hole through which the water dripped into a second container. A pointer floating in the second container indicated the passage of time, and an adjustment could be made to keep the passage of hours correct — the length of the hours varying between summer and winter, each day between sunrise and sunset being divided into twelve equal parts.

Ktesibios realized that as the level, and pressure, of water on the main jar dropped, the outflow would vary, and that later hourly intervals would be longer than earlier ones. He removed the inaccuracy by providing a constant water supply to the main jar and by the use of a float and valve ensuring that the head of water was constant. The water dripping into the second jar then accurately recorded the passage of time. Simple as the method appeared to be, it remained the most accurate time-keeping device until the invention of the pendulum clock in the seventeenth century.

Also important was Hero — sometimes described as Heros or Heron — of Alexandria, the Greek mathematician and writer. Although the general lines along which engineering developed in the ancient world are known through the efforts of archaeologists, there have always been large gaps in detailed knowledge. That is true not only of the dates and places at which newly developed equipment was first used. It has been true, also, of the most influential men whose work occupied that area, difficult to define, which was bounded by science, engineering, architecture and technology. This is illustrated by Hero. Although he wrote three books dealing with mechanics, the properties of air, and the making of automata, the years during which he lived and worked were constantly argued about until the late 1930s. Some experts placed him in the second century BC, others as late as the second century AD and yet others gave him intermediate dates. Only in 1938 was it pointed out that his method of calculating the Great Circle distance between Rome and Alexandria rested on an eclipse that happened only once between 200 BC and AD 300 — on 13 March AD 62. This and other evidence was proof that he lived during the second half of the first century.

Few of Hero’s writings have survived intact, and some of those only through Arab translations discovered in modern times. However, certain of his inventions and devices are known, the most famous being a device that is sometimes called the world’s first steam engine. This consisted of a hollow sphere from which there projected two bent tubes. When water in the sphere was heated the steam coming from the tubes caused the sphere to revolve. His conversion of steam power into motion — as a result of the law of action and reaction spelt out by Isaac Newton sixteen centuries later — was never exploited by Hero. He did, however, describe a number of machines incorporating levers, pulleys, inclined planes and wedges by which human forces could be directed or multiplied. One that he is believed to have built opened temple doors automatically and apparently without human intervention. This was achieved by using an altar fire to warm air which drove water from a hollow sphere into a hanging cauldron. Weighted down by the water, the cauldron worked a series of pulleys which opened the doors and allowed them to remain open until the fire died down, the water was siphoned from the cauldron and the doors were automatically pulled shut.

Of the knowledge built up by the Greeks over the centuries little was put to practical use until the rise of the Romans. Much of what is known about their contribution to civil engineering comes from what are often called ‘the ten books’ on ‘Architecture’ by Marcus Vitruvius Pollio, a contemporary of Julius Caesar. In fact, it is only one smallish book with ten divisions dealing with such subjects as water supply and aqueducts, mechanics, building materials and public buildings. Employed as a military engineer and professional architect, a term which still doubled for that of civil