A 1650 first edition of Bernard Varens’s Geographia Generalis was donated to the Niels Bohr Library by Thomas W. Sills. This college textbook, a pioneer in fields now considered geophysics, was used by Isaac Newton as a student, and as a professor Newton edited a new edition. The book includes the “vortex” theory that René Descartes used to explain the Moon’s pull on ocean tides, and which Newton displaced with his theory of universal gravitation. The book is only five inches wide. Sills writes: “All Latin college textbooks prior to ~1670 were of this shape and size. At that time books were very expensive. Only wealthy students could enjoy the luxury of owning their texts... The Trinity College Library would rent such books by the hour to students like Newton,” who attended on a scholarship.