6 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



are atoms; nothing that exists can be destroyed; change 

 takes place in virtue of the combination or separation of 

 atoms. Atoms are always in motion and are endless in 

 number and variety; they move about in space; they 

 press upon one another in every direction; they assume 

 eddying movements which give origin to new worlds : but 

 everything happens according to a definite sequence of law, and 

 nothing by chance. Even the soul consists of very finely 

 divided atoms which permeate the body and call forth the 

 phenomena of life. 



In opposition to the materialistic view of the atomic philo- 

 sophy, Anaxagoras of Clazomenae (bom 501 B.C.) regarded the 

 soul (vovs) as in itself a conscious, moving force. In his cosmic 

 philosophy he supposes an original chaos in which a circular 

 movement gives place to a universe, and at the same time 

 effects a differentiation of ether, air, and water. The earth 

 rises from the water, and receives seeds from the air which 

 develop into living plants and animals. The earth is poised 

 as a cylinder in the centre of the whole universe, and the stars 

 move round it. 



As the influence of the Sophists and Platonic philosophy 

 came more into ascendency, it tended to elevate dialectic and 

 speculative methods and to depreciate the investigation of 

 natural phenomena. Cultivated and gifted as the Athenians 

 of this epoch were, natural science owes but a small debt to 

 them. 



Plato (427 B.C.), in his Cosmology, is a follower partly of 

 Heraclitus and partly of Anaxagoras. According to Plato, the 

 universe is the production of divine intelligence and of the 

 necessary development of nature. The form of the whole 

 universe is spherical ; in the centre lies the earth as a motion- 

 less sphere; around it are the sun and the planets, and the 

 fixed stars occupy the outermost circle. All the heavenly 

 bodies are inhabited; the atoms composing them are indivisible, 

 and unite along definite limiting surfaces ; the universe itself is 

 unchangeable and indestructible. 



An interesting account is given in the "Tirnasus" of a 

 submerged Atlantic continent (Atlantis) on the other side of 

 the Pillars of Hercules (Gibraltar). The idea of such a sub- 

 merged continent has again received credence in recent geo- 

 logical researches. In Plato's account Atlantis was larger than 

 Asia and Libya together, it had been inhabited 9000 years 



