One of the most important figures in Danish literary culture was N. F. S. Grundtvig (1783–1872) who instilled a growing spirit of nationalism based initially on his "Northern Mythology" (1808) and his long drama, "The Fall of the Heroic Life in the North" (1809). In addition to a huge stream of articles and poems, he wrote a number of books, including two histories of the world (1814 and 1817), the long historical poem "Roskilde-Riim" ("Rhyme of Roskilde") (1813), and a book-sized commentary, "Roskilde Saga". Grundtvig's hymn book brought about a great change in Danish church services, substituting the hymns of the national poets for the slow measures of the orthodox Lutherans. In all Grundtvig wrote or translated about 1,500 hymns, including "God's Word Is Our Great Heritage", most of which are still frequently sung today.