The largest sheet of water on the globe, occupies a third of its whole surface, as much as all the land put together. It is a wide oval in shape, lying between Australia and Asia on the W., and North and South America on the E. Except from Asia it receives no large rivers. On its American shores the Gulf of California is the only considerable indentation; the Okhotsk, Japanese, Yellow, and Chinese Seas, on the Asiatic coast, are rather wide bays shut in by islands than inland seas. Its innumerable islands are the chief feature of the Pacific Ocean. The continental islands include the Aleutian, Kurile, Japan, and Philippine Islands, and the archipelago between the Malay Peninsula and Australia; the Oceanic Islands include countless groups, volcanic and coral, chiefly in the southern hemisphere, between the Sandwich Islands and New Zealand. Commerce on the Pacific Ocean is only beginning, but will increase vastly with the extension of the United States westward, the colonisation of Australia, and the opening of Chinese and Japanese ports. San Francisco and Valparaiso on the E., Hong-Kong and Sydney on the W., are just now the chief centres of trade.