Altaian and Kirghiz type. Farther east, around Lake Baikal, nomad Buriat tribes, a northern branch of the Mongol race, held out for many years against the Cossacks, but were finally subdued. The continuous raiding of these nomads into the Cossack forts and stockades, and the absence of any natural boundary to shut them out, of necessity caused the Cossacks to move southward, as opportunity presented itself, to secure subjugation of these Tartars. The first line of defence in Western Siberia during the eighteenth century reached Chornafsky, on the Tobol River, Omsk at the junction of the Om and Irtish rivers, Büsk on the Upper Obi. A second hue of defence, beyond this, stretched some hundred versts up the Tobol River, to what is now Semipalatinsk. South of these Cossack hues the Kirghiz Tartars roamed and raided, while south-east lay the great natural sanctuary of the Altai Mountains, into the plateaus of which the Altai Tartars and other relics of the Finnish races had been retreating for centuries past.
The Cossack defences consisted of block houses and stockades established across the steppes, between which communications were kept up. This means of defence; although unsatisfactory was only a temporary expedient, and prepared the way for farther advances into the steppe for the purpose of occupying the territory beyond, and of pushing all those who would not submit farther away, till some natural geographical line was reached.
The Russian system of sedentary agricultural colonization was in direct antagonism to the nomad life of the Tartar, and, as was the case in European Russia, so in Siberia these two economic systems were
