Prof. Norton on Molecular Physics, 425 



In a similar manner we also obtain 



pQ,=p 1 Q, l +j)< 2 Q 2 + ... 

 ^R=j3 1 R 1 +^ 2 R 2 + ... 



The present theory therefore does not only afford an expla- 

 nation of the constancy of the refractive power and of the for- 

 mula for mixtures, but it defines these laws even more distinctly 

 than before, and in particular shows that the refractive power 

 must diminish with the refractive index: this is fully con- 

 firemd by experiment. And these results may suffice us on this 

 occasion ; for it is needless to enter further into the details of 

 experiment, partly because it is self-evident that a closer agree- 

 ment can be obtained with two constants than with one, and 

 partly because our formulae are yet only approximately true. 



In conclusion, it will not be uninteresting to see how the various 

 phenomena of light instruct us as to the internal constitution of 

 material bodies. Double refraction indicates to us, in the first 

 place, the regular stratification of crystals, a character which is 

 also revealed by their external properties. The thickness of the 

 layers cannot, however, be deduced from double refraction, for 

 this would not cease even if the thickness were infinitely small ; 

 circular polarization, on the other hand, and especially the 

 more general chromatic dispersion, prove that this is not the 

 case, and that in all bodies, the elastic fluids scarcely excepted, 

 there is a stratification of measurable dimensions. Circular 

 polarization further indicates a want of symmetry in the interior 

 of certain crystals, which is likewise evidenced by their external 

 characters ; and the rare occurrence of this kind of polarization 

 teaches us that such a want of symmetry is not the common 

 case. Finally, the refractive power indicates that the limit of 

 the periodicity in the interior of bodies is on one side of a 

 vacuum, and therefore that material bodies consist of separate 

 transparent molecules. 



LII. On Molecular Physics, By Prof. W. A. Norton. 



[Continued from p. 389.] 

 Heat. 



THE general nature of heat, and the general cause of its evolu- 

 tion, have already been considered (p. 196). According to 

 the fundamental ideas presented, heat must be developed when- 

 ever the electric atmospheres of the molecules of any substance 

 are urged into closer proximity to the atoms which they surround. 

 Any disturbance of the equilibrium of the particles of a given 

 mass, or any change in the relations of the particles of any body 

 to those of other bodies, which may have the effect of producing 

 Phil. Mag. S. 4. Vol. 28. No. 191. Dec. 1864. 2 F 



