The double river-systems of the Volga and Kama, the Ob and Irtysh, the Angara and Yenisei, the Lena and Vitim on the Arctic slope, and the Amur and Sungari on the Pacific slope, are instances.
Asia, the same fauna extending in Siberia as far as the Yenisei and the Lena.
The Ob,Yenisei and Lena,which traverse Siberia, are among the largest rivers in the world.
The northern land-mass begins in the north with the area which lies between the Yenisei and the Lena.
It had long the reputation of being almost constantly ice-bound, but after the Norwegian captain Johannesen had demonstrated its accessibility in 1869, and Nordenskield had crossed it to the mouth of the Yenisei in 1875, it was considered by many to offer a possible trade route between European Russia and the north of Siberia.