As to unions between cities for peaceful purposes, they were of quite common occurrence. The intercourse which had been established during the period of liberation was not interrupted afterwards. Sometimes, when the scabini of a German town, having to pronounce judgment in a new or complicated case, declared that they knew not the sentence (des Urtheiles nicht weise zu sein), they sent delegates to another city to get the sentence. The same happened also in France;(26) while Forli and Ravenna are known to have mutually naturalized their citizens and granted them full rights in both cities. To submit a contest arisen between two towns, or within a city, to another commune which was invited to act as arbiter, was also in the spirit of the times.(27) As to commercial treaties between cities, they were quite habitual.(28) Unions for regulating the production and the sizes of casks which were used for the commerce in wine, "herring unions," and so on, were mere precursors of the great commercial federations of the Flemish Hansa, and, later on, of the great North German Hansa, the history of which alone might contribute pages and pages to illustrate the federation spirit which permeated men at that time. It hardly need be added, that through the Hanseatic unions the medieval cities have contributed more to the development of international intercourse, navigation, and maritime discovery than all the States of the first seventeen centuries of our era. In a word, federations between small territorial units, as well as among men united by common pursuits within their respective guilds, and federations between cities and groups of cities constituted the very essence of life and thought during that period. The first five of the second decade of centuries of our era may thus be described as an immense attempt at securing mutual aid and support on a grand scale, by means of the principles of federation and association carried on through all manifestations of human life and to all possible degrees. This attempt was attended with success to a very great extent. It united men formerly divided; it secured them a very great deal of freedom, and it tenfolded their forces. At a time when particularism was bred by so many agencies, and the causes of discord and jealousy might have been so numerous, it is gratifying to see that cities scattered over a wide continent had so much in common, and were so ready to confederate for the prosecution of so many common aims. They succumbed in the long run before powerful enemies; not having understood the mutual-aid principle widely enough, they themselves committed fatal faults; but they did not perish through their own jealousies, and their errors were not a want of federation spirit among themselves.