This unusual map is a very scarce example of early thematic cartography. It depicts ocean currents, volcanoes and deep-sea chasms; each is marked by the appropriate symbol noted in the title cartouche. The continents are void of political detail and only major lakes, rivers and volcanoes are shown. There are prominent Northwest and Northeast Passages and a vast southern continent. The magnificently decorative title cartouche is formed within a florid pediment supported by cherubs. The map is based on Happel and Kircher's theories of 1675. Zahn was a philosopher of the Praemonstratensian order at Wurzburg who wrote a number of pseudo-scientific works.
References: Shirley #583.
A nice impression on a bright sheet of watermarked paper with a short centerfold separation in the top blank margin and a bit of mat burn outside of the image.