The tributaries of the Dnieper are very numerous and important; their total length is over 13,000 km. Of those on the right, the Pripet River is the most important. It gathers in all the waters of the Polissye and is the typical river of that district. Its length exceeds 650 km. Rising in the northern spurs of the Volhynian Plateau, very close to the course of the Buh, it immediately reaches the Polissian Plain and becomes a navigable river over 50 m. wide and about 6 m. deep. In the main axis of the Polissian basin the Pripet turns eastward and becomes about 100 m. wide. The incline of the river is very slight, the number of turns and river arms enormous. Between swampy woods and moors the river forms labyrinths of delicate, intricate waterways and stagnant pools. Near Mosir, where the river turns to the southeast, its width reaches 450 m., its depth 10 m. Of quite the same type are the tributaries of the Pripet: the Turia, Stokhod, Stir with the Ikva, the Horin with the Sluch, the Ubort and the Uz on the right; the Pina, Yassiolda, Sluch and Ptich on the left. All of them are navigable along great stretches. The remaining right-hand tributaries of the Dnieper, the Teterev and the Irpen, have the Polissian character [81]only near their mouth, otherwise they are purely plateau rivers with rocky beds. The Teterev is able to transport rafts of logs, while the other rivers of the Dnieper Plateau, as for example, the Ross (altho greater than the Teterev) and the Tiasmin, are entirely unfit for navigation, as a result of their rocky beds and their small volume in summer. The last large Dnieper tributary, the steppe-river Inhuletz, altho barely 100 km. shorter than the Pripet, is, for the same reasons, only capable of carrying logs in the last 150 km. of its much-twisted course. Of the left-hand tributaries of the Dnieper only the northern ones possess a sufficient volume of water to be navigable. The Soz, which is 550 kilometers in length, becomes as wide as 150 meters, and is navigable for a stretch of nearly 360 kilometers. The Desna is the longest of all the Dnieper tributaries (1000 km.). It rises near Yelnia, on the Central Russian Plateau, and flows in a broad symmetrical valley, which it floods in places every spring to the extent of 10 kilometers. The normal width of the river at low-water is 160 meters; the depth is 6 meters. Despite many shallows and sand-banks, the Desna is capable of bearing rafts along a stretch of 250 kilometers, and is navigable for 700 kilometers even for the larger river boats. Of the Ukrainian tributaries of the Desna, the most important is the Sem, which is 650 km. long and navigable for 500 kilometers.