whence it extends across 30 degrees of latitude southwards to China and Turkestan, forming its southern frontiers."[1] This vast region, of an area of about 4,833,500 square miles, is larger than Europe and more than twice the size of European Russia, and forms one-fourth of the whole Asiatic continent. In the south its parallel is roughly 50° N., and its West meridian is 60° E.
The Siberian frontiers are very inaccessible. In the south the mountains and deserts divide it from China; in the east mountains separate it from the seas, and these seas, especially the Okhotsk Sea, are not navigable, because of the ice and fog. It is true that in the north Siberia is open to the sea, but the Arctic Ocean is not available for permanent navigation, in spite of the many attempts at finding "a north-east passage" and in spite of Nordenskiöld's success in passing through it. Only the west Siberian frontier is more accessible to the European, thanks to the low middle Ural Mountains, and thanks to the nearness of the Siberian rivers; and through this way all the migrations of people, first from Northern Asia to Europe, and then from Europe to Northern Asia, were possible.
With regard to the structure and geology of the Siberian surface one can divide it into:—(A) Western Siberia, of tertiary formation,[2] consisting of the flat, marshy country between the Yenisei River and the chain of the Ural Mountains; and (B) Eastern Siberia, situated east of the Yenisei, of older geological formation, rising here and there into hills difficult of access, culminating in high mountains on the south and east of the Lena River, and stretching to the extreme north-east along the mountains that form the watershed of the Pacific slope.[3]
A third physical district can be differentiated in Siberia, the Amur region, draining east of the watershed into the
