Until the early 19th century, Australia was best known as "New Holland", a name first applied by the Dutch explorer Abel Tasman in 1644 (as ''Nieuw-Holland'') and subsequently anglicised. ''Terra Australis'' still saw occasional usage, such as in scientific texts. The name ''Australia'' was popularised by the explorer Matthew Flinders, who said it was "more agreeable to the ear, and an assimilation to the names of the other great portions of the Earth". Several famous early cartographers also made use of the word Australia on maps. Gerardus Mercator used the phrase ''climata '' on his double cordiform map of the world of 1538, as did Gemma Frisius, who was Mercator's teacher and collaborator, on his own cordiform wall map in 1540. Australia appears in a book on astronomy by Cyriaco Jacob zum Barth published in Frankfurt am Main in 1545.