National Geographic : 1962 May
Coastal mountains cradle the icecap that overlies four fifths of Greenland. Hun dreds of glaciers pour ma jestically from the ice into bays and fiords rimming the world's largest island. Arctic convoy, a series of tractor trains known as a swing, averages three miles an hour between Thule and Century. Caterpillars with extrawide treads tow sledg es laden with as much as 100 tons. Wanigans- trailers mounted on skis and fitted with bunks, mess halls, and showers- make up the com 720 mand train (not shown).