The Danube, like most rivers of our northern hemisphere, presses upon its right bank, and this accounts for the difference between its Wallachian and Bulgarian banks. The latter, gnawed by the floods, rises steeply into little hills and {160} terraces, whilst the former rises gently, and merges almost imperceptibly in the plains of Wallachia. Swamps, lakes, creeks, and the remains of ancient river beds form a riverine network, enclosing numerous islands and sand-banks. These channels are subject to continual change, and to the south of the Yalomitza may still be seen a line of swamps and lagoons, which marks the course of an ancient river no longer existing. The lowlands on the Wallachian side of the Danube are constantly increasing in extent, whilst Bulgaria continuously suffers losses of territory. The latter, however, is amply compensated for this by the salubrity of its soil and the fine sites for commercial emporiums which it offers. It is said that the beaver, which has been exterminated almost in every other part of Europe, is still common in these half-drowned lands of Wallachia. At a distance of thirty-eight miles from the sea, in a straight line, the Danube strikes against the granitic heights of the Dobruja, and abruptly turns to the north, subsequently to spread out into a delta. In the course of this détour it receives its last tributaries of importance, viz. the Moldavian Sereth and the Pruth. Thirty miles below the mouth of the latter the Danube bifurcates. Its main branch, known as that of Kilia, conveys about two-thirds of the entire volume of its waters to the Black Sea, and forms the frontier between Rumania and Turkish Bulgaria. The southern branch, or that of Tulcha, flows entirely through Turkish territory. It separates into two branches, of which that of Sulina is the main artery of navigation.