THE BALTIC PROVINCES. 



229 



drainage is to Lake Peipus, and tbrough the Narova to the Gulf of Finhmd. 

 In the west the Pernau, Livonian Aa, Dvina, and Kurhmd Aa flow to the 

 Gulf of Riga, while the Windau and the less important streams full into the Baltic. 

 None of them are of any size except the Dvina (Diina of the Germans, Daugava of 

 the Letts, Zapadnaya Dvina, or Western Dvina, of the Russians), which discharges 

 about 18,000 cubic feet per second, draining a total area of 30,000 square miles, 

 where there is an approximate annual rainfall of 20 inches. Gathering the 



waters of the western and 



^, IT -ij • t J.-U Fis:. 110. — Parallel Hills of Dorp at. 



southern Valdai slopes, the ° ^ , __^ 



^ Scale 1 : 300,000. 



Dvina flows first south-west, 

 below Vitebsk trending Avest 

 and north-west, its low and 

 marshy banks in many places 

 retaining the traces of former 

 beds. According to the pre- 

 sent relief of the land its 

 natural course would be 

 southwards to the Dnieper. 

 But the changes of level, or 

 the erosions produced in the 

 course of ages, have enabled 

 it to open a passage between 

 the Silurian plateaux of 

 Livonia and Kurland, and 

 thus reach the Baltic. In 

 the rocky regions the navi- 

 gation is seriously obstructed 

 by rapids, giving a total fall 

 of about 174 feet in 87 miles, 

 but very unequally distri- 

 buted. 



Below Riga the river 

 ramifies into several 

 branches, winding through 

 an old lacustrine bed for- 

 merly separated from the sea 

 by a range of dunes. Little 



Dvina, Red Dvina, Old Dvina, and similar names recall the vagaries of the 

 stream, and sundry structures— forts, mills, dykes, and the like — are figured on 

 the maps, now to the north, now to the south of the ship channel. Near its 

 mouth it is joined by the Kurland Aa, known in its lower courses as the Bolder 

 Aa. About 4 miles from the junction the Aa has recently thrown oiï a branch 

 directly to the Gulf of Riga, and it may thus sooner or later cease to be an affluent 

 of the Dvina. 



5 Miles. 



