MEDI/EVAL SCIENCE IN THE WEST 



interest, since it has been used by his detractors, who 

 accuse him of lack of originality, to prove that his 

 seeming inventions and discoveries were in reality 

 adaptations of the Arab scientists. It is difficult to 

 determine just how fully such criticisms are justified. 

 It is certain, however, that in this part he describes 

 the anatomy of the eye with great accuracy, and dis- 

 cusses mirrors and lenses. 



The magnifying power of the segment of a glass 

 sphere had been noted by Alhazen, who had observed 

 also that the magnification was increased by increasing 

 the size of the segment used. Bacon took up the 

 discussion of the comparative advantages of segments, 

 and in this discussion seems to show that he under- 

 stood how to trace the progress of the rays of light 

 through a spherical transparent body, and how to 

 determine the place of the image. He also described 

 a method of constructing a telescope, but it is by no 

 means clear that he had ever actually constructed 

 such an instrument. It is also a mooted question as to 

 whether his instructions as to the construction of 

 such an instrument would have enabled any one to 

 construct one. The vagaries of the names of terms 

 as he uses them allow such latitude in interpretation 

 that modern scientists are not agreed as to the prac- 

 ticability of Bacon's suggestions. For example, he 

 constantly refers to force under such names as virtus, 

 species, imago, agentis, and a score of other names, and 

 this naturally gives rise to the great differences in the 

 interpretations of his writings, with corresponding 

 differences in estimates of them. 



The claim that Bacon originated the use of lenses, 



45 



