Roger Bacon 
Opus Majus, Volumes 1 and 2 [PDF ebook] 

The Opus Majus of Roger Bacon (c.1214-92) is one of the most influential scientific and philosophical texts of its age and arguably the high point of medieval knowledge of the physical sciences. In the work Bacon makes a plea for the reform of education, emphasizing the rightful role of the sciences in the university curriculum and the interdependence of the various disciplines.
Prepared in 1267 at the request of Pope Clement IV, the treatise is a collection of ideas, an encyclopedia of knowledge embracing all science, including language, logic, optics, mathematics, moral philosophy, and physics.