Gerardus Mercator believed in the existence of a large Southern continent on the basis of cosmographic reasoning, set out in the abstract of his "Atlas or Cosmographic Studies in Five Books," as related by his biographer, Walter Ghim, who said that even though Mercator was not ignorant that the Austral continent still lay hidden and unknown, he believed it could be "demonstrated and proved by solid reasons and arguments to yield in its geometric proportions, size and weight, and importance to neither of the other two, nor possibly to be lesser or smaller, otherwise the constitution of the world could not hold together at its centre".