As the sable had gradually led the Russian fur-hunters to Kamchatka, so the still more valuable sea-otter gave the chief impulse to the discovery of the Aleutic chain and the opposite continent of America. When Atlassow and his band arrived at Kamchatka by the end of the seventeenth century, they found the sea-otter abounding on its coasts; but the fur-hunters chased it so eagerly that, before the middle of the eighteenth century, they had entirely extirpated it in that country. On Bering’s second voyage of discovery (1741–42), it was again found in considerable numbers. Tschirigow is said to have brought back 900 skins, and on Bering’s Island 700 sea-otters--whose skins, according to present prices, would be worth about £20,000--were killed almost without trouble. These facts, of course, encouraged the merchants of Jakutsk and Irkutsk to undertake new expeditions. Generally, several of them formed an association, which fitted out some hardly seaworthy vessel at Ochotsk, where also the captain and the crew, consisting of fur-hunters and other adventurers, were hired. The expenses of such an expedition amounted to the considerable sum of about 30,000 roubles, as pack-horses had to transport a great part of the necessary outfit all the distance from Jakutsk, and the vessel generally remained four or five years on the voyage. Passing through one of the Kurile Straits, these expeditions sailed at first along the east coast of Kamchatka, bartering sables and sea-otters for reindeer skins and other articles; and as the precious furs became more rare, ventured out farther into the Eastern Ocean. Thus Michael Nowodsikoff discovered the Western Aleuts in 1745; Paikoff the Fox Islands in 1759; Adrian Tolstych almost all the islands of the central group, which still bear his name, in 1760; Stephen Glottoff the island of Kadiak in 1763, and Krenitzin the peninsula of Aljaska in 1768. When we consider the scanty resources of these Russian navigators, the bad condition of their miserable barks, their own imperfect nautical knowledge, and the inhospitable nature of the seas which they traversed, we can not but admire their intrepidity. In the Polar Sea there are neither sables nor otters, and thus the islands lying to the north of Siberia might have remained unknown till the present day, if the search after mammoth-teeth had not, in a similar manner, led to their discovery.