For mutual defence, the industrial towns of the north formed a league called the Hanse of London, because London was the seat of the chief counting-house. This league at first included only seventeen cities, with Ypres and Bruges at the head, but the association afterward increased to fifty or sixty, stretching as far west as Le Mans, as far south as the Burgundian frontier, and as far east as Liège. Exclusive of the royal domain, which was well consolidated under Philip Augustus, the French portion of this region substantially comprised the counties of Blois, Vermandois, Anjou, Champagne, and the Duchy of Normandy. This district, which has ever since formed the core of France, became centralized at Paris between the beginning of the reign of Philip Augustus in 1180 and the reign of Philip the Fair a century later, and there can be little doubt that this centralization was the effect of the accumulation of capital, which created a permanent police. The merchants of all the cities of the league bound themselves to trade exclusively at the fairs of Champagne, and, to prosper, the first obstacle they had to overcome was the difficulty and cost of transportation. Not only were the roads unsafe, because of the strength of the castles in which the predatory nobility lived, but the multiplicity of jurisdictions added to taxes. As late as the end of the thirteenth century, a convention was made between fifteen of the more important Italian cities, such as Florence, Genoa, Venice, and Milan, and Otho of Burgundy, by which, in consideration of protection upon the roads, tolls were to be paid at Gevry, Dôle, Augerans, Salins, Chalamont, and Pontarlier. When six imposts were levied for crossing a single duchy, the cost of importing the cheaper goods must have been prohibitory. The Italian caravans reached Champagne ordinarily by two routes: one by some Alpine pass to Geneva, and then through Burgundy; the other by water to Marseilles or Aigues-Mortes, up the Rhone to Lyons, and north, substantially as before. The towns of Provins, Troyes, Bar-sur-Aube, and Lagny-sur-Marne lie about midway between Bruges and Ypres on the one side, and Lyons and Geneva on the other, and it was at these cities that exchanges centralized, until the introduction of the mariner’s compass caused traffic to go by the ocean, and made Antwerp the monied metropolis. The market was, in reality, open continuously, for six fairs were held, each six weeks long, and the trade was so lucrative that places which, in 1100, had been petty villages, in 1200 had wealth enough to build those magnificent cathedrals which are still wonders of the world.