SCIENCE IN THE ANCIENT WORLD 47 



in the years 1589 to 1591, appealing to actual experi- 

 ments carried on from the top of the leaning tower of 

 Pisa, showed that heavy and light bodies do fall at the 

 same rate, and thus destroyed the Aristotelian con- 

 ception of heaviness and lightness as essential qualities 

 of bodies. 



Aristotle, too, though he accepted the spherical 

 form of the earth, maintained the geocentric theory 

 of the Universe, and his authority did much to prevent 

 the heliocentric theory of Aristarchus from being 

 accepted in the next generation, and obstructed 

 its revival by Copernicus seventeen hundred years 

 later. 



But nevertheless Aristotle was the greatest col- 

 lector and systematizer of knowledge produced by 

 the ancient world. His supreme importance in the 

 history of science consists in the fact that, till the 

 Renaissance of learning in modern Europe, no ap- 

 preciable advance in our knowledge of nature was 

 made in all the centuries that followed him. The 

 task of the Dark Ages was to preserve what it could 

 glean of his works from imperfect and incomplete 

 abstracts ; and later mediaeval times spent their 

 strength in recovering his meaning when the full 

 text of his books reappeared in the West. Aristotle's 

 works are an encyclopaedia of the learning of his 

 generation, and, save in physics and astronomy, he 

 probably made real improvement in all the subjects 

 he touched. He gives careful descriptions of animals, 

 their life-histories and habits ; he laid good foundations 

 for the modern science of comparative anatomy, 

 and, the first embryologist, watched the heart beating 

 in the chick while yet in the egg. Even in physiology, 



