50 SCIENCE OF THE MIDDLE AGES. FT. ii. 



distance at which you usually see small objects distinctly. 

 This observation of Alhazen's about the bending inwards or 

 co7iverging of rays through rounded glasses was the first step 

 towards spectacles. 



Besides the Arabians whom I have mentioned here, 

 there were many who were very celebrated, but we know 

 very little of their works. Among them was Avicenna 

 A.D. 980, whom you will often hear mentioned as a writer on 

 minerals. But the chief thing to be remembered, besides 

 the discoveries of Geber and Alhazen, and the introduction 

 of the Indian numerals, is that in the Dark Ages, when all 

 Europe seemed to care only for wars and idle disputes, it 

 was the Arabs who kept the lamp of knowledge alight and 

 patiently led the way to modem discoveries. 



