When news of the crushing disaster reached Sibir the Russians, losing heart at the death of their leader, evacuated the place and returned home. The czar, nevertheless, had no idea of permitting a land so promising to slip from his grasp. It was not long before he sent a larger army across the Ural Mountains, which not only reconquered the lost territory but also the rest of western Siberia. [Illustration: Gathering salt at the mouth of the Ural River] Gradually the Cossacks moved eastward, conquering tribe after tribe. As they advanced they built strong wooden forts by which to hold their vantage ground. Tomsk was founded in 1604; by 1630 the tide of conquest had reached the banks of the Lena; and within eighty years from their first conquest the Russians had reached the Pacific. Years afterward a suitable monument was erected to Yermak in the city of Tobolsk, which was built on the battle-field where he gained his first decisive victory over the Tartar ruler. His real monument is all Siberia, whose conquest he inaugurated. In 1847 the Amur River section was annexed by Russia regardless of the protests of the Chinese Government. Quarrels ensued over the boundaries and, finding resistance hopeless, the Chinese ceded to Russia all the land on the left bank of the Amur as far as the mouth of the Ussuri and on both its banks below that river. The sable gradually led the Russian hunters to Kamtchatka, while the more valuable sea-otter beckoned them across the sea to the Aleutian Islands and that part of the American continent now Alaska Territory. The chief incentive in all of these conquests was the securing of valuable furs. The sable is even yet found along the streams in both open and forested sections from the Ural Mountains to the Pacific; but so relentless has been the pursuit of this valuable fur-bearing animal that it is now nearly exterminated. Besides the sable and the sea-otter, there are found in Siberia the ermine, bear, arctic fox, common fox, deer, wolf, antelope, elk, hare, and squirrel. To avoid entering into conflict with the more powerful people at the south, the Russians chose to advance eastward along higher latitudes toward the Pacific. But within a few years after the Muscovite empire had acquired central and northern Siberia, there were loud complaints that the tribes on the south were making raids on them, robbing them of their property and carrying their people into slavery. So, from time to time, Cossack forces were sent to chastise the offenders; and in many instances they were punished and their territories were annexed to Siberia. In these raids the Turkomans were the most active. During the forty years previous to 1878 it is estimated that eighty thousand Russian subjects and two hundred thousand Persians were made captives and sold into slavery. In 1873 the Russians captured Khiva and liberated thirty thousand Persian slaves.