Continent world ultimately persisted with these being regarded as separate continents. From the late 18th century, some geographers started to regard North America and South America as two parts of the world, making five parts in total. Overall though, the fourfold division prevailed well into the 19th century. Europeans discovered Australia in 1606, but for some time it was taken as part of Asia. By the late 18th century, some geographers considered it a continent in its own right, making it the sixth (or fifth for those still taking America as a single continent). In 1813, Samuel Butler wrote of Australia
Continent as "New Holland, an immense island, which some geographers dignify with the appellation of another continent" and the "Oxford English Dictionary" was just as equivocal some decades later. Antarctica was sighted in 1820 during the First Russian Antarctic Expedition and described as a continent by Charles Wilkes on the United States Exploring Expedition in 1838, the last continent identified, although a great "Antarctic" (antipodean) landmass had been anticipated for millennia. An 1849 atlas labelled Antarctica as a continent but few atlases did so until after World War II. From the mid-19th century, atlases published in the United States more commonly