The greater part of the land on the earth’s surface is grouped into two
great _hemispheres_, the Old and the New World. The former and far
larger of these consists of Eurasia in the north, separated by
ill-defined boundaries from Europe to the west and Asia to the east, and
of Africa in the south, united to Eurasia by the narrow neck of the
isthmus of Suez. The hemisphere of the New World is divided into North
America and South America, united by the long, narrow isthmus of Central
America. The island of Australia is also reckoned as a continent. It is
believed that an island continent, Antarctica, surrounds the South Pole.
Of islands not reckoned as continents, the largest is the polar island
of Greenland.