The universal geography : earth and its inhabitants

TEE BALTIC PROVINCE*. 229drainage is to Lake Peipus, and through the Narova to the Gulf of Finland.In the west the Pernau, Livonian Aa, Dvina, and Kurland Aa flow to theGulf of Riga, while the TVindau and the less important streams fall into the Baltic.Xone of them are of any size except the Dvina (Diina of the Germans, Daugava ofthe Letts, ZapacLnaya Dvina, or Western Dvina, of the Russians), which dischargesabout 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 thewaters of the western andsouthern Valdai slopes, theDvina flows first south-west,below Vitebsk trending westand north-west, its low andmarsh}' banks in many placesretaining the traces of formerbeds.According to the presentrelief of the land itsnatural course would besouthwards to the Dnieper.But the changes of level, orthe erosions produced in thecourse of ages, have enabledit to open a passage betweenthe Silurian plateaux, ofLivoniaand Kurland, andthus reach the Baltic. Inthe rocky regions the navigationis seriously obstructedby rapids, giving a total fallof about 174 feet in 87 miles,but very unequally distributed.Below Riga the riverramifies into severalbranches, windingthroughan old lacustrine bed formerlyseparated from the seaby a range of dunes.LittleFig. 110.Parallel Hills of DoRrAT.Scile 1 : 300,000.Dvina, Red Dvina, Old Dvina, and similar names recall the vagaries of thastream, and sundry structures—forts, mills, dykes, and the like—are figured onthe maps, now to the north, now to the south of the ship channel. Near itsmouth it is joined bj T the Kurland Aa, known in its lower courses as the BolderAa. About 4 miles from the junction the Aa has recently thrown off a branchdirectly to the Gulf of Riga, and it may thus sooner or later cease to be an affluentof the Dvina.V