PLAINS OF THE ELBE, ODER, AND YISTULA. 309 



either by ice or by floods. All tbe efforts of engineers have hitherto failed in 

 converting the Oder into a serviceable river highway. 



The Oder, discharging itself into a tideless sea, has no estuary. Below Stettin 

 the river flows through an elongated lake, which is gradually being silted up, 

 and then enters the Grosse Haf, a great fresh-water lagoon, covering 307 

 square miles. Two islands separate it from the open Baltic, with which it com- 

 municates through three channels, of which two are spanned by bridges and closed 

 by bars, leaving only that of Swine, in the centre, available for navigation. It 

 was formerly obstructed by a bar having less than 8 feet of water over it ; but 

 jetties have been constructed, and the depth is now 16 feet. The lagoon itself is 

 shallow, and the construction of a navigation canal across it is under con- 

 sideration. 



The Vistula — called Weichsel by the Germans, Wisla by the Poles — is bounded 

 by swamps, now partly drained and protected by embankments. These latter, 

 however, do not always prove efhcacious when the ice breaks up in spring. In 

 1855 the rising floods burst through the embankments designed to control them, 

 inundating a vast extent of country. As the river flows from south to north, 

 the ice breaks up first in its upper part, and not being able to escape, it accumu- 

 lates, damming up the river, and ultimately acts with almost irresistible force. 

 The bridge of Dirschau has had to be furnished with powerful ice-breakers to 

 resist its pressure. 



The Lower Vistula forms a natural boundary between the plains of Germany 

 and Russia. . The country to the west of it is sandy and covered with pine woods, 

 whilst to the east extends a more varied region of greater fertility, and clothed 

 with forests of deciduous trees. At a distance of 25 miles from the sea we reach 

 the head of the" delta, the Nogat, or eastern arm, flowing into the Frische Half, 

 whilst the main branch of the river discharges itself directly into the sea below 

 Danzig. 



The delti of the Vistula has an area of 620 square miles, and grows visibly. 

 Its alluvial soil is of exceeding fertility. Formerly the whole of it was a swamp, 

 but the embankments constructed since the latter part of the thirteenth century 

 have rendered its cultivation possible. The Teutonic knights, who had established 

 themselves at Marienburg, first took this work in hand, employing thousands of 

 Lithuanian and Slav prisoners. In six years they raised embankments protecting a 

 Weixler, or island, of 350 square miles. The Werders near Danzig and Elbing 

 were embanked in the beginning of the fourteenth century, and it is astonishing 

 that such works should have been accomplished in an age when the art of the 

 engineer was still in its infancy. 



The Frische Haff covers an area of 330 square miles, but was much larger 

 formerly, having partly been filled up by the alluvial deposits of the Vistula and 

 Pregel. If the coast of Prussia were not slowly subsiding, we might be able to 

 calculate the number of years required to convert the whole of it into dry land. 



The Pregel forms a delta too, and that a most remarkable one, for Sam- 

 land, the district bounded by its main arm and the lateral branch which flows 



