Thus the liberties of Holland and Flanders waxed, daily, stronger. A great physical convulsion in the course of the thirteenth century came to add its influence to the slower process of political revolution. Hitherto there had been but one Friesland, including Holland, and nearly all the territory of the future republic. A slender stream alone separated the two great districts. The low lands along the Vlie, often threatened, at last sank in the waves. The German Ocean rolled in upon the inland Lake of Flevo. The stormy Zuyder Zee began its existence by engulfing thousands of Frisian villages, with all their population, and by spreading a chasm between kindred peoples. The political, as well as the geographical, continuity of the land was obliterated by this tremendous deluge. The Hollanders were cut off from their relatives in the east by as dangerous a sea as that which divided them from their Anglo-Saxon brethren in Britain. The deputies to the general assemblies at Aurich could no longer undertake a journey grown so perilous. West Friesland became absorbed in Holland. East Friesland remained a federation of rude but self-governed maritime provinces, until the brief and bloody dominion of the Saxon dukes led to the establishment of Charles the Fifth's authority. Whatever the nominal sovereignty over them, this most republican tribe of Netherlanders, or of Europeans, had never accepted feudalism. There was an annual congress of the whole confederacy. Each of the seven little states, on the other hand, regulated its own internal affairs. Each state was subdivided into districts, each district governed by a Griet-mann (greatman, selectman) and assistants. Above all these district officers was a Podesta, a magistrate identical, in name and functions, with the chief officer of the Italian republics. There was sometimes but one Podesta; sometimes one for each province. He was chosen by the people, took oath of fidelity to the separate estates, or, if Podesta-general, to the federal diet, and was generally elected for a limited term, although sometimes for life. He was assisted by a board of eighteen or twenty councillors. The deputies to the general congress were chosen by popular suffrage in Easter-week. The clergy were not recognized as a political estate.