140 THE GREEK ASTRONOMY. 



distance, so that the lamp alone is visible, should run on turning him- 

 self round ; we should see the light sometimes stationary, sometimes 

 retrograde, but on the whole progressive. 



A mechanism of this kind was imagined for each of the planets, 

 and the wheels of which we have spoken were in the end called 

 Epicycles. 



The application of such mechanism to the planets appears to have 

 arisen in Greece about the time of Aristotle. In the works of Plato 

 we find a strong taste for this kind of mechanical speculation. In the 

 tenth book of the " Polity," we have the apologue of Alcinus the 

 Pamphylian, who, being supposed to be killed in battle, revived when 

 he was placed on the funeral pyre, and related what he had seen dur- 

 ing his trance. Among other revelations, he beheld the machinery by 

 which all the celestial bodies revolve. The axis of these revolutions 

 is the adamantine distaff which Destiny holds between her knees ; on 

 this are fixed, by means of different sockets, fiat rings, by which the 

 planets are carried. The order and magnitude of these spindles are 

 minutely detailed. Also, in the "Epilogue to the Laws" (Epinomi-s), 

 he again describes the various movements of the sky, so as to show a 

 distinct acquaintance with the general character of the planetary mo- 

 tions ; and, after speaking of the Egyptians and Syrians as the origin il 

 cultivators of such knowledge, he adds some very remarkable exhorta- 

 tions to his countrymen to prosecute the subject. "Whatever we 

 Greeks," he says, " receive from the barbarians, we improve and per- 

 fect; there is good hope and promise, therefore, that Greeks will carry 

 this knowledge far beyond that which was introduced from abroad." 

 To this task, however, he looks with a due appreciation of the quali- 

 ties and preparation which it requires. " An astronomer must be," 

 he says, " the wisest of men ; his mind must be duly disciplined in 

 youth ; especially is mathematical study necessary ; both an acquaint- 

 ance with the doctrine of number, and also with that other branch of 

 mathematics, which, closely connected as it is with the science of the 

 heavens, we very absurdly call geometry, the measurement of the earth."* 



These anticipations were very remarkably verified in the subsequent 

 career of the Greek Astronomy. 



The theory, once suggested, probably made rapid progress. Sim- 

 plicius 5 relates, that Eudoxus of Cnidus introduced the hypothesis of 

 revolving circles or spheres. Calippus of Cyzicus, having visited Pole- 



Epinomis, pp. 988, 990. 5 Lib. ii. de Calo. Bullialdus, p. 18. 



