GEMMA Frisius, Reinerus (1508-1555). De principiis astronomiae et cosmographia. Colonia: Cholinus, 1578 - [Legato con:] EUCLIDE. Elementorum geometricorum libri sex. Ingolstad: Eder, 1617 - Two scientific works: Gemma's astronomical treatise published the year after his renown observation of the comet of 14 november 1577 buond with an illustrated edition of Euclid. 2 works in one volume, 8vo (145 x 90mm). Title of first work partially coloured in red with woodcut vignette, full-page woodcut, initials and headpieces; second work with woodcut vignette and numeours wooducts (margin of first title restored without loss, few occasional stains and browned leaves). Later vellum, manuscript title on spine (panels with cuts). Provenance: early exlibri on title.