Clavis Universi Trigonometrica per Quam Coeli ac Terrae Adyta recludi, & omnes de Motibus ac Dimensionibus utriusque per Hypotheses artificum Triangulari forma conceptae quaestiones per certa Problemata resolvi & in apertum produci possunt… Accedunt Tabulae pro negocio hoc trigonico

Finely engraved added title & numerous woodcut diagrams & printed tables in the text. Printed title in red & black. 9 p.l. (incl. engraved title), 323, 184 pp. Two parts in one vol. Large 4to, cont. vellum over boards, covers nicely decorated with coats-of-arms in gilt & silver (now oxidized) on each cover, a.e.g., ties gone. Hamburg: Frobenius, 1634.

First edition of this handsome and rare work on trigonometry by a student of Tycho Brahe. Frobenius (1566-1645), after studying in Tübingen and Wittenberg, went in 1591 to the island of Hven where he intended to live and study with Tycho Brahe. Upon leaving, he wrote a recently (truncated) discovered memorandum (see John Robert Christianson’s On Tycho’s Island. Tycho Brahe and His Assistants, 1570-1601), which is full of “critical insight” on Tycho and his relationships with his students and assistants. Later, Frobenius moved to Hamburg where he married well and became a leading printer, publisher, and bookseller of that city, specializing in learned and scientific works. He wrote and self-published a number of works — like this one — a number of works on trigonometry, astronomy, and philology.

The first part of the present book is devoted to spherical trigonometry as applied to astronomy and the text contains many references to Brahe and Longomontanus. The second part includes the famous trigonometric tables of Rheticus, which first appeared in 1596.

A very fine and large copy with the Nordkirchen bookplate. The attractive engraved title-page, present here, is usually missing

❧ Poggendorff, I, 809. Tomash & Williams F101. (Inventory #: 6761)