Mathematical Treasure: Johann Placentinus’s Geotomia

Johann Placentinus was a professor of mathematics and astronomy in Brandenburg and Frankfurt in the 17th century. In his 1657 Geotomia of approximately 75 unnumbered pages, he used logarithms and trigonometry to explore geometrical problems on globes, such as measuring distances between latitudes or longitudes. He apparently remained attuned to the religious and political conflicts that comprised the Thirty Years’ War, which had devastated central Europe until 1648, for he quoted Philip Melanchthon (1497–1560), the Lutheran reformer, and he dedicated the volume to Elizabeth Stuart (1596–1662), the wife of Bohemian Elector Frederick V—who was defeated by Catholic forces in the 1620s—and the daughter of England’s James I. Two pages written in German instead of in Latin indicate Placentinus was also close to his colleague, the German hymnwriter Heinrich Held (1620–1659).

A full digitization of the copy owned by the University of Michigan is available from GoogleBooks.

Index to Mathematical Treasures