(formerly called, also, the South Sea), that immense expanse of water which extends between the North and South American continents and Asia and Australia. It is the largest of the oceans, exceeding in compass the whole of the four continents taken together, and occupying more than a fourth part of the earth's area and fully one-half of its water surface. On the west it extends to the Indian Ocean and has several more or less distinct seas connected with it-China Sea, Yellow Sea, Sea of Japan and Sea of Okhotsk; on the north it communicates with the Arctic Ocean by Bering's Strait, on the south it is bounded by the Antarctic Ocean, and on the east it joins the Atlantic at Cape Horn. Within this enormous circumference it includes the numerous islands composing the groups of Australasia and Polynesia and those adjoining America and Asia. The average depth of the Pacific appears to be greater than that of the Atlantic, and its bed is less irregular. The deepest soundings known are 5155 fathoms (30,930 feet), north of New Zealand, and 5269 fathoms (31,614 feet), off the island of Guam. In the Pacific the tides never attain the maximum heights for which some parts of the Atlantic and Indian oceans are celebrated. The trade winds of the Pacific are not so regular in their limits as those of the Atlantic, and this irregularity extends over a much wider region in the case of the southeast trade wind than in the case of the northeast. The cause of this is the greater number of islands in the South Pacific Ocean, which, especially in the hot season, disturb the uniformity of atmospheric pressure by local condensations. The northeast trade wind remains the whole year through within the northern hemisphere. The southeast trade wind, on the other hand, advances beyond the equator (See TRADE WINDS). In the Chinese seas the terrible typhoon occasionally rages and may occur at any season of the year (See TYPHOON). The Portuguese were the first Europeans who entered the Pacific. Balboa, in 1513, discovered it from the summit of the mountains which traverse the Isthmus of Darien. Magellan sailed across it from east to west in 1520-1521. Drake, Tasman, Bering, Anson, Byron, Bougainville, Cook, Vancouver, Laperouse and others traversed it in different directions in the seventeenth and eighteenth centuries.