l8 SCIENCE OF THE GREEKS, ft. i. 



CHAPTER III. 



320 to 212 B.C. 



School of Science at Alexandria — The Ecliptic and the Zodiac — Greeks 

 believed that the Sun moved round the Earth — Aristarchus knew 

 that it was the Earth which moved — He also knew of the Obliquity 

 of the Ecliptic, and that the Seasons are caused by it — He knew 

 that the Earth turns daily on its Axis — Euclid discovers that Light 

 travels in straight lines — Archimedes discovers the Lever — 

 Principle of the Lever — Hiero's Crown, and how Archimedes dis- 

 covered the principle of Specific Gravity. 



While Aristotle was studying science at Athens, the Greeks 

 under Alexander the Great were making great conquests in 

 Egypt, where Alexander founded a city bearing his own 

 name on the shores of the Mediterranean. After Alexan- 

 der's death this city, called Alexandria, fell to the portion of 

 Ptolemy Lagus, one of Alexander's generals, who was suc- 

 ceeded by a number of princes of the same name. The 

 Ptolemies were all patrons of learning and science, and the 

 school of Alexandria became one of the most famous the 

 world has ever known. By this time the Greeks had learnt 

 many astronomical facts, some of them probably from the 

 Egyptians. They had traced the ecliptic, or the sun's appa- 

 rent yearly path through the heavens, and, dividing this path 

 into twelve parts, they called each division by the name of a 

 constellation or cluster of stars. These constellations re- 

 ceived most of them the names of animals, and therefore 

 the circle of the twelve constellations was called the Zodiac^ 



