the Luminiferous Ether. 



239 



of light through various substances placed in the magnetic 

 field follows as a consequence of the influence exerted by the 

 magnet on the molecules of the body. 



In conclusion, in the following Table is drawn up a compa- 

 rative view of the explanations and assumptions made in the 

 two theories of the various phenomena of light. 



Phenomena. 



Fundamental 

 assumption. 



Refraction . . . 



Colour 



Calorescence 



and 

 fluorescence. 



Radiation and 

 absorption... 



Double refrac- 

 tion 



Chemical 

 action 



Ether Theory. 



Light is transmitted by the 

 vibrations of an elastic and 

 all-pervading medium. 



The elasticity or density of 

 the ether is altered by its 

 contiguity to the mole- 

 cules of the refracting 

 body. 



The ether particles vibrate 

 with different degrees of 

 velocity for different co- 

 lours. 



The impact of the ethereal 

 waves causes the ether in 

 the bodies to vibrate, 

 sometimes with greater, 

 sometimes with less velo- 

 city than the particles of 

 ether in these waves. 



The oscillation of the mole- 

 cules of the radiating body 

 throws the particles of 

 ether in the surrounding 

 medium into vibration. 

 This vibration causes the 

 ether in the absorbing 

 body to vibrate ; and the 

 vibration of this ether 

 causes the molecules of the 

 absorbing body to vibrate. 



Owing to the different group- 

 ing of the molecules of the 

 crystal, the elasticity or 

 density of the ether in 

 which these molecules are 

 contained is altered. 



The vibration of the parti- 

 cles of the ether in which 

 the molecules of the 

 body are contained shakes 

 these molecules, so as in 

 one case to overcome the 

 bond of chemical union be- 

 tween the atoms of the 

 molecule, in the other case 

 to cause the atoms to com- 

 bine. 



Molecular Theory. 



Light is transmitted by the 

 vibrations of the mole- 

 cules of bodies. 



\ 



| The molecules of different 

 )■ bodies move with diffe- 

 rent degrees of freedom. 



The molecules vibrate more 

 J- rapidly for some colours 

 than for others. 



The impact of the molecular 

 waves causes the mole- 

 cules of the bodies to vi- 

 brate. 



The molecules of the radi- 

 ating body vibrate ; this 

 throws the molecules of 

 the surrounding medium 

 into vibration ; and these 

 throw the molecules of 

 the absorbing body into 

 vibration. 



The freedom of the mole- 

 cules to vibrate is diffe- 

 rent in different planes, 

 owing to the molecular 

 constitution of the crys- 

 tal. 



The vibration of the mole- 

 cules of the body causes 

 in one case the force of 

 chemical affinity to be 

 sxispended ; in the other, 

 it causes the force to be 

 brought into action. 



