I now come to the plan of uniting the _islands_, formed by these early inhabitants. They availed themselves for that purpose of all such parts of the sand-banks as lay in the intervals between the large islands, and were beginning to produce grass. These, when surrounded with dikes, are what are called _Hoogs_; and their effects are to break the waves, thus diminishing their action against the dikes of the large islands, and, at the same time, to determine the accumulation of the mud in the intervals between those islands. In this manner a large _marsch_ island, named Everschop, was already, in 987, united to Eyderstede by the point on which Poppenbull is situated; and in 995, the union of the same _marsches_ was effected by another point, namely, that of Tetenbull. Lastly, in the year 1000, Eyderstede received a new increase by the course of the Hever, prolonged between the sand banks, being fixed by a dike; but the whole still remained an _island_. This is an example of the manner in which the _marsch_ islands were united by the _hoogs_; and the chronicle of the country says, that, by these labours, the islands were so considerably enlarged in size, and the intervals between them so much raised, that, at low water, it was possible to pass on foot from one to the other. The extent of these _marsches_ was so great on the coast of Sleswigh alone, that they were divided into three provinces, two of which comprehended the islands, and the third comprised the _marsches_ contiguous to the coast; and the same works were carried on upon the _marsches_ of the coast of Holstein. But the grounds thus gained from the sand-banks were very insecure; these people, though they had inhabited them more than ten centuries, had not yet understood the possibility of that combination of fatal circumstances above described, against which their dikes formed but a very feeble rampart; the North Sea, by the extraordinary elevations of its level, being much more formidable in this respect than the ocean, where the changes of absolute level are much less considerable. I shall give an abridged account of the particulars extracted by M. Hartz from the chronicle of Dankwerth, relative to the great catastrophes which these _marsches_ successively underwent, previously to the time when experience led to the means necessary for their security.