An Encyclopedia of the History of Technology part 46 pot

PART THREE: TRANSPORT 432 support them. These were the first true roads. The Romans, the first real road- builders, appreciated the need for adequate drainage, a proper foundation and a cambered, impermeable surface (see Figure 8.1). They constructed 372 major roads, a total of some 53,000 Roman miles (1 mile=1000 passus: 1 passus= 1.5m (5ft)). These military roads, connecting all the principal towns of the Roman empire from Africa to Scotland and from Spain to Greece generally followed the straightest possible routes and were largely paved with slabs of stone or lava. A map of the Roman roads of Britain shows a remarkable similarity to that of the modern motorway network. The legendary straightness of Roman roads derives, it is said, not from the prowess of their surveyors nor from their desire for the shortest route irrespective of gradient, but from a design weakness in their vehicles. There was no means of steering the front wheels of their four-wheeled wagons, used for baggage, fodder and trade. They could only be inched sideways to change course by means of crowbars. The theory is plausible but incapable of proof. With the retreat of the Romans and their armies from Britain between AD 410 and 436 little was done to maintain existing roads or build new ones. It was not until after the Norman invasion over six hundred years later that the military value of a good road system was again appreciated. It was, however, the Church which had the greatest influence and, until the dissolution of the monasteries by Henry VIII following his adoption of the position of the Supreme Head of the Church in England in 1534, it was the Church that bore the brunt of road maintenance, including the provision of inns or other accommodation where travellers could rest overnight and obtain refreshment. In 1555 an Act of Parliament was passed for ‘for amending the High-ways being now both very noisom and tedious to travel in and dangerous to all Passengers and Carriages’. Under this Act every parish was bound to appoint two of their number to act as Surveyors and Orderers. At first four and later six days were fixed upon which ‘two able men with a team and tools convenient to work 8 hours upon every one of those days’ from ‘everyone having a term or Ploughland’ while every cottager was ‘bound to work himself or find a sufficient labourer to work for him’. The tendency was to elect as waywardens the least popular and most incompetent men of the parish and for Figure 8.1: Section of a typical Roman road. ROADS, BRIDGES AND VEHICLES 433 them to attend only to the roads that they themselves habitually used, to the neglect of the rest. The worst standards of repair were in parishes where no stone was available except by the pillaging of ancient monuments, either buildings or previous roads. Probably the greatest failing of the parish system was that it was too localized: it fragmented the responsibility for road maintenance into tiny divisions at a period when few people travelled outside a radius often or fifteen miles of their home in their whole lifetimes. Thus any conception of a parish road forming a part of the national network of inter-city communications was non-existent. No priority was given to the upkeep of trunk roads passing through the parish. The first Turnpike Act of 1663, ‘for repairing the High-ways within the Counties of Hertford, Cambridge and Huntingdon’, established a new principle and a new system. By this time both people and goods were travelling longer distances and more frequently, churning up the old roads, which were mostly ungraded and unpaved, more than ever. Yet it was not for another century that many investors had money available to put into turnpikes, for passage along which a charge was made. By 1750 there were only 169, twenty years later 530, but over 1100 by the 1830s, just at the time when the age of the railway was being born to sound the death knell of road transport—until the introduction of the internal combustion engine some fifty years later. By a Turnpike Act, the trustees, originally the justices of the locality concerned, were empowered to charge a toll according to a scale laid down in the Act, the income from such charges to be devoted to the upkeep of the carriageway. In 1706–7 a precedent was established to allow bodies consisting of persons other than the justices to become trustees and to petition Parliament for an Act. The system was hardly a success, since the government made no decisions as to the highways that were of most importance, so that turnpikes grew up and spread haphazardly without any overall plan, the stretches of main road that were included being so purely fortuitously. In the 1830s nearly 4000 trusts were responsible for 35,400km (22,000 miles) of road out of a total estimated at 169,000km (105,000 miles). Worse still was the fact that no systematic or scientific approach was made until about 1756 to the construction and maintenance of highways, whether turnpikes or not. The techniques of the Romans, expensive but effective, had long been forgotten. It was John Metcalfe of Knaresborough, blind since smallpox at the age of six, followed by Thomas Telford and John Loudon McAdam, who were to change all this. In 1765, ‘Blind Jack’ Metcalfe contracted to build a turnpike road three miles long between Harrogate and Boroughbridge in Yorkshire. By 1792 he had constructed over 290km (180 miles) of roads. He had an uncanny knack of choosing the best routes over undulating territory, travelling the country for surveys quite alone and unaided by companion or assistant. Most important, however, was his recognition that a well-drained, dry foundation was the first essential, laying a smooth surface of stones over bundles of ling or heather set PART THREE: TRANSPORT 434 on a foundation of prepared subsoil, the roadway being raised above ditches for drainage, dug at the sides. It is doubtful if he had heard of Robert Phillips, who in 1737 had read a paper to the Royal Society in which he described a construction on similar principles. The blind Metcalfe, it should be mentioned, was so independent that he served in a volunteer regiment during the Scottish rebellion of 1745. No record exists of his having shot any of his own side. Thomas Telford was trained as a stonemason, becoming Surveyor of Public Works for the County of Salop (Shropshire) in 1787. In this capacity he was much concerned with turnpike roads within the county. In 1803 he was appointed to direct the construction and improvement of roads in the Highlands of Scotland with a view to improving that country’s economy, for the previous road works of General George Wade had been for purely military purposes. By 1820, Telford had built 1500km (920 miles) of new roads which involved 1117 bridges. If they knew nothing of the principles of good road construction, the authorities were at least aware of some of the major causes of destruction of their roads. The pressure on the road surface was principally a function of the load and the area of tyre in contact with it. Wheel width was of prime importance, narrow wheels, heavily loaded, causing deep ruts, a problem that was to receive much attention in parliamentary Acts from 1750 onwards. In 1753 wagons with wheels less than nine inches wide were prohibited unless drawn by oxen or at least five horses. Teams of eight, twelve or even more beasts were more common. Daniel Defoe, in his Tour Through the Whole Island of Great Britain (1724–6), describes a ‘tug’ carrying a tree to the dockyard at Chatham which was pulled by no less than twenty-two oxen. In spite of this the timber was left to weather throughout a winter when the road surface was churned into a morass. In 1765 someone had the bright thought that, if the front wheels of a wagon were set closer together than the rear wheels, and both pairs were sufficiently wide, the would in effect act as a roller on a good width of the roadway. Freedom from tolls was accordingly granted to such wagons for a period of five years. In fact France was the first nation to develop a systematic approach to roadbuilding, largely through the work of Pierre J.M.Trésaguet, starting about 1764. The government had established a school a few years earlier, l’Ecole des Ponts et Chaussées, to train men for the work of overseeing the construction of roads and bridges. Trésaguet laid a single layer of 15–18cm (6–7in) stones on edge on a base of cambered subsoil, covered them with an equal layer of stones of about 5cm (2 in) diameter and topped this with 8cm (3in) of ‘pieces broken to about the size of a small walnut’ (see Figure 8.2). A network of many hundreds of miles of Trésaguet’s construction was built in France and this was so successful that it extended into many other European countries. Telford’s method of construction was remarkably similar, but the subsoil base that he used was flat instead of convex in section. It had at the foundation a similar ROADS, BRIDGES AND VEHICLES 435 layer of flat 15–18cm (6–7in) stones placed on edge and tightly packed. Many miles of roads in Britain today follow the tracks of Thomas Telford’s ideal alignments and gradients. Telford’s methods were expensive in first cost, in fact too expensive for many of the turnpike trusts, who preferred to adopt the construction of John Loudon McAdam which lasted well enough with a minimum of maintenance. McAdam’s principle was that ‘it is the native soil which really supports the weight of the traffic; while it is presented in a dry state it will carry any weight without sinking’. This was certainly true of the loads that were transported by road in McAdam’s day, although with the modern juggernaut truck, there might be some doubts, unless the weight was distributed between a sufficient number of axles. McAdam, an Ayrshire man, made a fortune in America and then returned to his native country to become a road trustee and later, in 1815, Surveyor-General of the Bristol roads. His concept of putting ‘broken stone upon a road, which shall unite by its own angles, so as to form a solid hard surface’ was a sound one, the size of the stones being closely controlled and the way being drained by side ditches. Ideally a 15cm (6in) layer was laid, a further 15cm (6in) being added some weeks later, after traffic had consolidated the first layer. To ensure that the stones were all of the same size his surveyors were equipped with a 6-ounce (170g) weight and scales or alternatively a 2-inch Figure 8.2: Sections of typical roads by Tresaguet, Telford and McAdam. PART THREE: TRANSPORT 436 (5cm) ring gauge. It is related that he evolved the latter after inspecting a length of newly laid road one day and finding that a whole stretch of it was of stones of a much bigger size. Up until then the rule was that only stones that could be put into a man’s mouth were to be used. The workman responsible for the stretch was admonished, but responded to the rebuke with a broad grin, revealing a capacious and entirely toothless mouth. No finer material was laid on top, as McAdam found that the iron tyres of coaches and wagons ground off chips of stone to fill in the voids in the mass as they passed over it. He was a prolific writer on road building and his books were translated into several languages, thus popularizing the McAdam system abroad. During his lifetime and after his death, his three sons William, James and John Loudon junior continued his road-building work, and by 1823 they had been responsible for 85 trusts comprising over 2000 miles of road. It was not until 1824 that the problem of properly surfacing the streets of towns was tackled. On the advice of Thomas Telford, a 30cm (12in) deep foundation of broken stones was covered with granite setts about 30cm (12in) long by 15cm (6in) wide and 25cm (10in) deep to withstand the density of traffic. These were far more durable than the cheap cobbles which had been used in the principal streets, at least on those where paving was considered necessary at all. Raised pavements with kerbstone edges had been introduced in Westminster and the City of London in the 1760s. An alternative to granite was the creosoted wood block road surface, the timber for which was mainly imported from Russia from 1838 onwards. A few of these wooden-surfaced city streets survived in Britain into the 1950s. Trunk roads changed little until the introduction of Dunlop’s pneumatic tyre (see p. 449), which became increasingly popular for motor cars from the end of the nineteenth century. Pneumatic rubber tyres had a suction effect that drew up the fragmented stone particles that had been compacted between the stones by the passing of traffic, and dust became a problem. Macadam surfaces made of tar (distilled from wood or coal) or asphalt (a by-product of petrolem) were thus shortly introduced to suppress the problem. Motorways A motorway is defined today as ‘a limited access road with grade separation, completely fenced in, normally with hard shoulders…for the exclusive use of prescribed classes of motor vehicles’. The motorway concept is remarkable in that it originated so early: only some twenty years after Benz and Daimler produced the first motor cars. In 1906 a road, virtually of motorway standards, was proposed from London to Brighton though nothing came of the proposal. The same result came from the plan to build ‘the Northern and Western Motorway’ from London to Liverpool in 1923. ROADS, BRIDGES AND VEHICLES 437 The first road ‘solely for the use of motor vehicles’ dates from 1914 when a 65km (40.5 miles) long single-carriageway road with limited access was built in the USA on Long Island. A 10km (6 miles) experimental dual carriageway with no access along its length was built in 1921 to the west of Berlin. Construction of motorways or autostrade increased greatly with Italian activity from the 1920s. A road from Milan to Varese, some 80km (50 miles), was opened in 1925 and later extended a further 50km (31 miles) to Lake Como and Lake Maggiore. In the next ten years seven other motorways, amounting to a total of some 400km (248.5 miles) were built throughout Italy. The German government’s plan for a network of motorways (autobahn) started in 1923 and was pursued energetically after the National Socialists came to power in 1933. These were dual carriageways with a central reservation having an anti-dazzle hedge. By 1939, 3300km (2050 miles) of autobahns were completed and in use, 2000km (1243 miles) under construction and a further 3300km (2050 miles) planned. The first motorway in Britain was the 13km (8 miles) Preston bypass, opened in 1958. By 1980, 2286km (1420 miles) of motorway were in use in England alone. Since then the 203km (126 miles) London Orbital motorway has been completed. Motorways in Britain take up some 30 acres per mile (76,000sq. metres per kilometre), usually of agricultural land. Modern roads have either flexible or rigid ‘pavements’, this term being used to describe the form of overall construction. Flexible pavements deflect under heavy loads and flex slightly to accommodate movements due to settlement. Macadam and asphalt are typical ‘black-tops’ of this type. Rigid pavements are constructed of concrete. The wearing course, which is 15–40mm (0.6in–1.6in) thick, of a flexible pavement is the top surface and is designed to give an even-running, durable and skid-resistant finish strong enough to resist the tractive forces from the traffic, and weather-resistant. Below this comes the base course of 40–75mm (1.6–3in) thickness and, with the upper wearing course, forming the surfacing. It distributes the traffic loading from the surface to the roadbase. The thickness of the roadbase depends on the intensity of the traffic for which the road was designed and the material of which it is made. It is at least 60mm thick. The sub-base is laid directly on the finished earthwork, the top layer of which is termed the formation. Concrete roads have thinner sub-bases than flexible roads, the concrete slabs providing the structural layer as well as the wearing surface. The slabs may or may not be reinforced, depending on the traffic loading and intensity for which the road is intended. Transverse joints filled with a sealing compound allow for expansion and contraction. The normal design life of rigid pavements is 40 years compared with 20 years for flexible pavements. PART THREE: TRANSPORT 438 EARLY ROAD TRANSPORT First the ox and then the horse were domesticated to become useful as draft animals, as were the mule, the ass and the donkey. Light two-wheeled chariots were used in warfare by many Middle Eastern nations and from them the tradition was handed down to the ancient Greeks and to the Romans. Both had two wheeled chariots as well as four-wheelers, used more for goods transport than for passengers. Chariot racing was popular as a sport before 770 BC. The Roman two-wheeled carpentum was a vehicle used by lower officials, including members of the priesthood. The carraca dormitoris, with four wheels, was equipped with beds. The carpentum mortuarium was a two-wheeled hearse. The decline in the state of the roads in Britain, after the departure of the Romans, was accompanied by a decline in the use of wheeled vehicles, coastal shipping and river transport being used instead wherever possible. Men, even royalty, preferred to travel on horseback throughout this period: a litter might be used by the aged or infirm or by women. This process continued throughout the Middle Ages up until the second half of the sixteenth century, when carriages and coaches began to be imported from the Continent. Initially carriage travel was mainly confined to towns, only baggage being sent by coach or wagon between towns. The poor, which included the great majority of the population, went on foot if they travelled at all. When wheeled passenger transport vehicles began to be imported from Europe, British manufacturers were not slow to copy them and here we see the beginnings of an indigenous coach- and carriage-building trade. The word ‘coach’ is derived from Kocs in Hungary, reputedly the place where they were first built. The first coach known to have been built in Britain was by Walter Rippon for the Earl of Rutland in 1555, while the Earl of Arundel imported one from Germany which was much copied. It is said that Queen Elizabeth I preferred to send to the Netherlands for her carriages though, in ceremonial processions, she also used a litter. A hundred years later the coaching business had grown to include the use of hackney carriages for hire in towns and regular stagecoach services between them. In 1635 the post became a royal monopoly, ‘His Majesty’s Mail’, and was carried by postboys—or occasionally girls—on horseback and very slowly until after a Post Office Act of 1765, when it was made an offence to convey the mail at less than 6 miles an hour. John Palmer’s first mail coaches started operating between London and Bath, a stagecoach journey of seventeen hours, in 1784, covering the distance in one hour less and with greatly increased regularity. The following year saw the introduction of regular mail-coach services all over the kingdom, including such remote destinations as Holyhead and Milford Haven. Four inside passengers were all that were carried. Besant’s ‘Coach for the Mails’, with his improved wheel, was patented in 1786. In this, a collar was formed on the arm of the axle and a plate made to bolt on the ROADS, BRIDGES AND VEHICLES 439 inner side of the nave of the wheel so that, unless the plate wore through completely, it was impossible for the wheel to come off, a great improvement over the conventional arrangement in which there was a washer and linch pin passing transversely through a hole in the end of the axle. Furthermore both the axle bearing and the face-plate were lubricated by means of an oil-cup and a groove along the axle. The improvements in speed, punctuality and service brought about by the introduction of the mail-coaches was largely dependent on the improved roads of Telford, Metcalfe and McAdam. There were many developments in coach design from the seventeenth century onwards which individually amounted to little but which collectively transformed the primitive vehicle which was little more than a box on wheels into the comparative speed and luxury of the mail coach, the landau or the brougham. Springs replaced the earlier suspension from leather straps. Dished wheels were introduced and the use of one-piece iron tyres followed soon after instead of short strips of iron nailed to the felloes of the wheels. Attempts were made to add some form of braking superior to the conventional iron wedge or skid attached by a chain to the perch (or chassis member) and slipped under the front of the nearside rear wheel, at some risk to the coachman, when approaching a descent. Lever brakes, operating a friction pad, usually of leather, to work against the wheel tyre, were not introduced until early in the nineteenth century. Goods vehicles changed little, but from 1780 onwards many new and improved passenger vehicles appeared, a number of them of continental origin. Of the many types of carriages, coaches, carts and wagons that originated between 1750 and 1900, the most important are listed with their principal characteristics in Tables 8.1 – 3. POWERED ROAD TRANSPORT: INITIAL EXPERIMENTS Until 1760, the only alternative to the roads was transport by river but, in that year, James Brindley started to build his first canal, to carry coal from the Duke of Bridgewater’s mines at Worsley through to Manchester. At first greeted with scepticism, the canal was so successful that the price of coal in Manchester was halved. The reduction in price led naturally to a great increase in trade. Soon canal schemes were started up and down the country and the moneyed classes hurried to invest in the wonders of the new inland waterway transport. The ‘canal boom’ reached its peak about 1793, in which year the Grand Junction Canal, from Oxford to Brentford, was started, the last of the network of canals that now threaded the country. A horse could draw a number of barges, each carrying a far greater load than a wagon, so freight transport moved wherever possible away from the turnpike roads and on to the canals (see Chapter 9). The boom was to be relatively short-lived, however, for the railway age was just over the horizon and was to have an even greater PART THREE: TRANSPORT 440 effect on the prosperity of both road and canal transport. It may be said to have started properly with the Rainhill Trials in 1829 (see p. 561). The middle years of the eighteenth century saw the beginning of serious attempts to produce a thermodynamic substitute for the faithful horse, and these were to increase as the cost of fodder soared during the Napoleonic Wars. The steam engine (see Chapters 5 and 11) was at that time the only possibility available. Nicolas Cugnot, a French military engineer, produced in 1769 a vast, Table 8.2: Larger carriages and coaches—private and coachman-driven. Table 8.1: Public vehicles. ROADS, BRIDGES AND VEHICLES 441 top-heavy, steam-driven contraption (Figure 8.3) that lumbered ponderously round a few of the streets of Paris. Its lack of speed has, been criticized, perhaps unjustifiably, for Cugnot had only intended it as a gun-carriage tractor. However, the military authorities showed little interest and it soon ended up as a museum piece. James Watt’s engineer, William Murdock, tried again in 1785 and produced a model of another three-wheeler of a much lighter design. His experiments were not appreciated and his master dissuaded him from wasting too much time on such a ‘trivial pursuit’, at pain of losing his job. William Symington, the Scottish engineer, designed a steam road carriage in 1796 and built a model which he demonstrated to prospective financial backers. Richard Trevithick persisted longer. After he had tested models, he drove his first full- sized carriage under steam in Cornwall in 1801. The relief of Trevithick and his cousin, Andrew Vivian, on righting it after it had overturned was so great that, when they stopped at an inn ‘to comfort their Hearts with a Roast Goose and proper drinks’, they were ‘forgetfull of the Engine, its Water boiled away, the Iron became red hot, and nothing that was combustible remained of the Engine or the house’ where it was sheltered. A second carriage (Figure 8.4) was built the following year and ran for some time in London, but created little interest, only Table 8.3: Privately-driven carriages. . inched sideways to change course by means of crowbars. The theory is plausible but incapable of proof. With the retreat of the Romans and their armies from Britain between AD 410 and 436 little was. construction, the authorities were at least aware of some of the major causes of destruction of their roads. The pressure on the road surface was principally a function of the load and the area of tyre. dissolution of the monasteries by Henry VIII following his adoption of the position of the Supreme Head of the Church in England in 1534, it was the Church that bore the brunt of road maintenance,