174 ANCIENT CLASSIFICATION. 



The ancient philosophers classified the material 

 world into four elementary divisions, fire, air, 

 earth, and water. They taught " the existence of 

 a universally diffused ethereal medium, pervading 

 all things, and manifest 3&fire when put in motion." 

 This ethereal medium they placed at the head of 

 elementary substances, as occupying all space not 

 occupied by other matter, and as being in contin- 

 ual motion. 



These unceasing motions we can trace, through 

 the momentum of the vast solar systems, to the 

 power of their " Unknown God." 



