COSMICAL ETllEll. 33 



are separated by two inter mediate elementary conditions, of 

 which the one, water, approximates most nearly to tlie heavy 

 earth, and the other, air, to the hghter element of fire.=*^ 



Considered as a medium filling the regions of space, the 

 otlier of Empedocles presents no other analogies excepting 

 those of subtlety and tenuity -with the ether, by whose trans- 

 verse vibrations modern physicists have succeeded so hap- 

 pily in explaining, on purely mathematical principles, the 

 ])ropagation of light, with all its properties of double refrac- 

 tion, polarization, and interference. The natural philosophy 

 of Aristotle further teaches that the ethereal substance pen- 

 etrates all the living organisms of the earth — both plants 

 and animals ; that it becomes in these the principle of vital 

 heat, the very germ of a psychical principle, which, uninflu- 

 enced by the body, stimulates men to independent activity.! 

 These visionary opinions draw down ether from the higher 

 regions of space to the terrestrial sphere, and represent it as 

 a highly rarefied substance constantly penetrating through 

 the atmosphere and through solid bodies ; precisely similar 

 to the vibrating light-ether of Huygens, Hooke, and modern 

 physicists. But what especially distinguishes the older Ionic 

 from the modern hypothesis of ether is the original assump- 

 tion of luminosity, a view, however, not entirely advocated 

 by Aristotle. The upper fire-air of Empedocles is expressly 

 termed brightly radiating (naiKpavocjv), and is said to be 

 seen by the inhabitants of the earth in certain phenomena, 

 gleaming brightly through fissures and chasms [x^^H'^^^) 

 which occur in the firmament.^ 



The numerous investigations that have been made in re- 

 cent times regarding the intimate relation betAveen light, 

 heat, electricity, and magnetism, render it far from improba- 

 ble that, as the transverse vibrations of the ether which 

 fills the regions of space give rise to the phenomena of light, 

 the thermal and electro-magnetic phenomena may likewise 



* Aristot., De CceIo, iv., 1, and 3-4, p. 308, and 311-312, Bekk. If 

 the Stagirite withholds from ether the character of a fifth element, 

 which indeed is denied hy R'lUer (Geschichte der Philosophie, th. iii., s. 

 259), and by Martin {Etudes sur le Timie de Platon., t. ii., p. 150), it is 

 only because, according to him, ether, as a condUion of tnatter, has no 

 contrary. (Compare Biese, Philosophie des Aristoteles, bd. xi., s. 6G.) 

 Among the Pythagoreans, ether, as a fifih element, was represented by 

 the fifth of the regular bodies the dodecahedron, composed of twelve 

 pentagons. (Martin, t. ii., p. 245-250.) 



t See the proofs collected by Biese. op. cit., bd. xi., s. 93. 



X Cosmos, vol. i., J). 153. 



B 2 



