47. Johannes Mejer maps. 1630s - a cartographic genius' posthumous works

'Papers in Royal Library' is how Danish Biographic Lexicon describes the 142 hand-drawn and coloured maps by Johannes Mejer (1606-74). He was born in Husum, where he also took up permanent residence as an adult. He was mathematically and technically gifted, and inspired by the Danish astronomers and mathematicians Tycho Brahe, Longomontanus and Lauremberg, he independently developed a number of surveying techniques. In 1636 he began a charting of the marshes around Husum and thereby attracted the attention of the Duke of Gottorp. In 1642 Christian IV requested him to chart the duchies in their entirety. He completed this work in 1648, one year after having been appointed royal Danish cartographer. At the request of Frederik III he produced an excellent map of Denmark. After that he charted Jutland (1655) and the eastern provinces of Denmark (1658). Mejer was simultaneously planning a large Nordic atlas, a total of seven volumes, but it was never finished, i.a. due to the country's hopeless finances after the peace of Roskilde.

Out of all Johannes Mejer's cartographic works, only the charting of the duchies was published. It consisted of 37 maps and is considered to be his finest work. In terms of detail and accuracy, Johannes Mejer's maps were far above other contemporary maps, and his unprinted maps were during the Great Nordic War secured for the Danish king's library immediately after the conquest of Tønningen and Gottorp Castle in 1713.

The rest of the Gottorp library - probably the largest spoils of war in Nordic history: 331 manuscripts and 12,000 printed books - was from a military-strategic point of view of lesser importance and did not come to The Royal Library until 1749. Several of Johannes Mejer's maps were in the 1700s copied for personal use by i.a. the historian Jakob Langebek. They were not printed until 1942, in three large volumes.