THE BELFAST ADDBESS. 



3. 



During the drought of the Middle Ages in Christen- 

 dom, the Arabian intellect, as forcibly shown by Draper, 

 was active. With the intrusion of the Moors into Spain, 

 order, learning, and refinement took the place of their 

 opposites. When smitten with disease, the Christian 

 peasant resorted to a shrine, the Moorish one to an 

 instructed physician. The Arabs encouraged transla- 

 tions from the Greek philosophers, but not from the 

 Greek poets. They turned in disgust ' from the lewd- 

 ness of our classical mythology, and denounced as an 

 unpardonable blasphemy all connection between the 

 impure Olympian Jove and the Most High God.' 

 Draper traces still farther than Whewell the Arab 

 elements in our scientific terms. He gives examples of 

 what Arabian men of science accomplished, dwelling 

 particularly on Alhazen, who was the first to correct the 

 Platonic notion that rays of light are emitted by the 

 eye. Alhazen discovered atmospheric refraction, and 

 showed that we see the sun and the moon after they 

 have set. He explained the enlargement of the sun 

 and moon, and the shortening of the vertical diameters 

 of both these bodies when near the horizon. He was 

 aware that * the atmosphere decreases in density with 

 increase of elevation, and actually fixed its height at 

 58 J- miles. In the 'Book of the Balance of Wisdom,' 

 he sets forth the connection between the weight of the 

 atmosphere and its increasing density. He shows that 

 a body will weigh differently in a rare and dense atmo- 

 sphere, and he considers the force with which plunged 

 bodies rise through heavier media. He understood the 

 doctrine of the centre of gravity, and applied it to the 

 investigation of balances and steelyards. He recognised 

 gravity as a force, though he fell into the error of 



