184 Mr KELLAND, ON THE DISPERSION OF LIGHT, 

 We have — = ^^ + 



IX e A 



and taking only a very approximate value, we obtain 



.-p, 



but the density evidently varies as the cube of the reciprocal of e, 



or density oc — . 



In conclusion, I would remark, that although what has here been 

 treated of has been but roughly and approximately developed, there 

 is good reason for supposing that the laws we have arrived at are 

 the correct ones, not only as regards the action of the particles of 

 aether, but as regards those of air also. 



The law of the inverse square of the distance has always appeared 

 to me a fiecessanj law; necessary, I mean, as regards the actual state 

 of the constitution of the Universe: and although I could allow that 

 the particles of matter might have been impressed with any law at 

 their creation, I cannot, in consistence with the simplicity of all known 

 actions, conceive any other than Newton's law. It is true, the phe- 

 nomena of Capillary Attraction seem to militate decidedly against it, 

 but no person that I am aware of has proved that the phenomena 

 could not arise from discontinuing the fluidity, and until that has been 

 done, I think (I speak with deference to others far more capable of 

 judging) we ought not to be too hasty in adopting a law of force, 

 however simply it may account for the particular phenomena in question, 

 which we have no reason to suppose is applicable to any others. 



But I fear I am trespassing beyond the proper limits of my subject, 

 and shall therefore proceed no further than merely to observe, that the 

 farther we proceed in our investigations, the more simple do our con- 

 clusions become, and that from the apparent discrepancies, as, for in- 

 stance, in the lateral spread of sound passing through an aperture, 

 which is not the case for light, in general arise the strongest confir- 

 mations of the unitv of the whole. 



