34 SPECIAL RESULTS IN THE URANOLOGICAL 



knowledge of the purer mountain air, comparatively free 

 from heavy terrestrial vapours ; or of the diminishing density 

 of the strata of air with increasing height. As the " elements" 

 of the ancients signify not so much diversity, or even sim- 

 plicity or indecomposability of substance, as " states of 

 matter/' the idea of the upper sether (the fiery celestial 

 atmosphere) had its root in the first and normal antitheses 

 of "heavy" and "light," "under" and "upper," "earth" 

 and " fire." Between these two extremes are two " middle 

 elementary states :" water, more 'nearly akin to the heavy 

 earth ; and air, nearer to the light fire. ( 64 ) 



As a space-filling medium, the aether of Empedocles has no 

 analogy, excepting by its tenuity and rarity, with the ether 

 by whose transverse vibrations modern physical science has 

 succeeded so happily in explaining, by pure mathematical de- 

 duction, the propagation of light and all its properties 

 (double refraction, polarisation, and interference). In the 

 natural philosophy of Aristotle it was also taught that the 

 sethereal substance pervaded and penetrated all organic beings, 

 plants, and animals ; that it became in them the principle of 

 vital heat, and even the germ of a psychical principle, which, 

 preserving itself distinct from the body, awakened men to 

 self-activity. ( 65 ) These imaginations draw down the aether 

 from upper space into the terrestrial sphere ; they present it 

 as an exceedingly fine substance constantly pervading and 

 penetrating both the atmosphere and solid bodies, as does 

 the ether in the undulatory theory of light, according to the 

 views of Huygens, Hooke, and our present physicists. But 

 that which most directly distinguishes the two hypotheses, the 

 ancient Ionian aether and the modern ether, from each other, 

 is the original assumption (not altogether shared, however, 



