t ; i:(rRA PHICA L SCIENCE. 



281 



the power to impart to him. He had constructed a sphere which imitated 

 tlit' motion of the heavens, and it was through the intermediary of astronomy 



and mathematics that he grappled with the most arduous questions of 

 geography. Roger Bacon, in the fourth part of his "Opus Ma jus," devoted 



o o 



