For the Vistula, with the Bug and Narew, see Poland.
The Bug, another right-hand tributary of the Vistula, describes a wide curve concentric with those of the middle Vistula and the Narew, and separates the Polish governments of Lublin and Siedlce from the Russian governments of Volhynia and Grodno.
Its tributary, the Narew (250 m.), brings the forest-lands of Byelovyezh in Grodno into communication with Poland, timber being floated down from Surazh and light boats from Tykocin in Lomza.
Coniferous forests, consisting mostly of pine (Pinus sylvestris) and birch, cover large tracts in Mazovia in the north, extend across the Baltic lake-ridge southwards as far as the confluence of the Bug with the Narew, and join in the south-east the Polysie of the Pripet.
And reaches three degrees farther north in small groups or isolated specimens; the confluence of the Bug and the Narew may be regarded as its eastern limit.
The town of Sierock, at the confluence of the Bug and the Narew, is fortified to protect the rear of Novogeorgievsk.