But even had the processes of production become more efficient, they would have been rendered useless by the inefficiency of the means of distribution. The older main roads, which had lasted fairly through the Middle Ages, had broken down in later times before the growth of traffic and the increase of wagons and carriages. The new lines of trade lay often along mere country lanes which had never been more than horse-tracks, and to drive heavy wains through lanes like these was all but impossible. Much of the woollen trade therefore had to be carried on by means of long trains of pack-horses; and in most cases the cost of carriage added heavily to the price of production. In the case of yet heavier goods, such as coal, distribution was almost impracticable, save along the greater rivers or in districts accessible from the sea. But at the moment when England was just plunging into the Seven Years' War the enterprise of a duke and a millwright solved this problem of carriage, and started the country on a mighty course of industry which was to change both its social and its political character. Francis, Duke of Bridgewater, was a shy, dreamy man, whom a disappointment in love drove to a life of isolation on his estates in the north. He was the possessor of collieries at Worsley whose value depended on their finding a market at the neighbouring town of Manchester; and it was to bring his coal to this market that he resolved to drive a canal from the mine to the river Irwell. With singular good luck he found the means of carrying out his design in a self-taught mechanic, James Brindley. But in Brindley's mind the scheme widened far beyond the plans of the duke. Canals, as he conceived them, were no longer to serve as mere adjuncts to rivers; on the contrary, "rivers were only meant," he said, "to feed canals"; and instead of ending in the Irwell, he carried the duke's canal by an aqueduct across that river to Manchester itself. What Brindley had discovered was in fact the water-road, a means of carrying heavy goods with the least resistance, and therefore the least cost, from the point of production to the point of sale; and England at once seized on his discovery to free itself from the bondage in which it had been held. From the year 1767, when Brindley completed his enterprise, a network of such water-roads was flung over the country; and before the movement had spent its force Great Britain alone was traversed in every direction by three thousand miles of navigable canals. [Sidenote: Mineral developement.]