It is hard to realize today, when we take for granted that one level or another of our government will provide new roads and bridges and be responsible for keeping them in good repair, that from the mid 17th through the 18th century the tremendous growth in transportation projects of all kinds - the new roads and bridges and canals and later the railroads - was financed and built by private capital.
Until the mid 17th century, the burden of maintaining and repairing the roads had been the obligation of the local rate payer. Each shire was responsible for the roads that crossed it. The assumption was that the traffic on those roads was local traffic. However, as prosperity and trade grew, so too did resentment at having to pay locally for the maintenance of a road now being used by strangers transporting goods to and from distant locations. Local resistance to now having to make repairs more frequently as well as there being no coordination of repairs along the length of the road from shire to shire, British roads continued to deteriorate.
The 1662 Act of Parliament enabling the formation of joint venture companies to finance and build private toll roads would totally revolutionize transportation and communication in the British Isles. Finally the design, construction and maintenance of major new long distance roads could be coordinated and consistent throughout the length of the new turn pike. These companies issued stock and paid dividends to the investors, a factor which played a role in another innovation affecting our story. Gradually, during the 18th century, the country was crisscrossed by new hard surface toll roads that were soon crowded with Royal Mail and regular stage coaches, with post chaises and wagons. There was a pressing need for new bridges.
Simultaneously with the building of toll roads, private capital was also building a network of canals. Large landowners such as Francis Egerton, 3rd Duke of Bridgewater (1736-1803) or the proprietors of iron works and coal mines or the owners of pottery works, such Josiah Wedgwood (1730-1795), were “eager to develop the trade of the area from which they derived their personal incomes” by linking the various natural waterways, especially in the mining and industrial districts, for the transportation of bulk goods and raw materials by barge. (The Industrial Revolution, T.S. Ashton, p66)
The men whom they hired to build the canals (and the roads and the bridges), such as James Brindley (1716-1772) and Thomas Telford (1757-1834), John Loudon McAdam (1756-1836) were working under contract as talented, self-taught individuals in a role that we would today describe as consulting civil engineers. The scope and complexity of the projects they successfully undertook “were larger than anything previously undertaken short of a military campaign.” (Ibid p 66). Their individual stories are as fascinating as the projects they built.
These canals also created a need for new bridges both to cross the canals and, in fact, to carry the canal itself across valleys, rivers, and even across other canals. The limiting factor was as always the tensile strength of the material being used. In the case of the canal bridges or aqueducts, it had to bear the great weight of the canal water as well as the weight of the structure itself. This greatly increased the cost of their construction. The time was ripe for the introduction of a new material for building bridges.
Simultaneously with this need came its solution. Although iron had never before been considered a satisfactory material for building structures under tensile stress, the “new” iron being made at the foundries of the Severn Valley would prove to be just the material that was needed to build these bridges.