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SCIENCE 



[N. S. Vol. XLVI. No. 1199 



beginnings of things station themselves 

 each in its right place by keen intelli- 

 gence. 



To Plato and his school, on the other 

 hand, the orderly course of nature can be 

 explained only as the incarnation of a di- 

 vine plan. So he conceived of the uni- 

 verse before the creation as consisting, on 

 the one hand, of chaos and disorder, mat- 

 ter without plan or qualities ; on the other 

 hand, of the eternal plan or soul of the 

 world existing in the mind of God. Then 

 the creator, taking this inert nothingness, 

 impressed upon it the eternal idea and the 

 whole becomes an organic unity. 



Thus the universe was created, un- 

 changing, unchangeable, and this idea, as 

 modified by Aristotle, became the current 

 coin of the intellectual world. Nearly 

 twenty centuries passed before the next 

 advance came with the realization that the 

 world did not spring into existence full 

 grown, but that its present state is the re- 

 sult of a long series of changes. 



Before this idea of progressive develop- 

 ment could be attained, it was necessary 

 that certain hoary fallacies should be cast 

 aside and correct notions substituted. Un- 

 til it was realized that the earth and the 

 other celestial bodies are spheres, and that 

 the sun, and not the earth is the center of 

 our own system, the progress of astronomy 

 and cosmology were slow and imperfect. 

 But these were concepts of very gradual 

 growth. 



In the early part of the fifth century 

 B.C., Parmenides, of Elea, wrote a short 

 poem on Nature, of which we still possess 

 a few fragments. In this he refers to the 

 spherical form of the earth, a truth which 

 he appears to have been the first of all 

 mankind to enunciate. Around the earth 

 as a center he conceived a series of con- 

 centric spheres on which were fixed the 



heavenly bodies, an idea which was not 

 without its supporters during the following 

 two thousand years. A little later it 

 seems to have been taught by Pythagoras. 

 Prom it his disciples and successors 

 framed their interesting theory of the 

 Cosmos, which was believed to consist of 

 the "central fire," the "hearth of the 

 universe," round which were ten concen- 

 tric spheres. There must be ten, for the 

 system is perfect, and according to their 

 idea, ten is the number of perfection. 

 These spheres bear in succession the fixed 

 stars, the five planets, the sun, the moon, 

 the earth and another celestial body, which 

 they called the "antichthon" and which 

 served as a screen between the earth and 

 the central fire. Around this blazing pivot 

 revolved the earth once in 24 hours, al- 

 ways facing outwards, and so bringing into 

 view the various parts of the heavens in 

 succession. Consequently the back of the 

 earth must always be dark. Therefore, if 

 one were to travel past India, there he 

 would find a land of perpetual twilight, 

 where neither the blessed light of the sun 

 nor the rays from the central fire could 

 ever penetrate. 



The spherical form of the earth was sub- 

 sequently taught by Plato, who, like all 

 that followed for two thousand years, 

 placed it in the center of the universe, and 

 finally, by Aristotle, who became, until the 

 Renaissance, the dominating figure in Eu- 

 ropean thought. 



But the development of correct cosmolog- 

 ical ideas was not destined to continue un- 

 interruptedly. In 389 the great library of 

 Alexandria was destroyed. Shortly after 

 came the fall of the Western Empire and 

 the long, dark night of the middle ages set 

 in. Most of the gains which science had 

 made during the previous centuries were 

 forgotten, and the Church, which then be- 

 came the custodian of all that was thought 

 worthy of preservation, set its face firmly 



