466 Prof. Challis on the Theory of Double Refraction 



Group. 



Names. 



Theoretical 

 distances. 



Totals. 



Actual 

 distances. 



Difference. 



Proportion 

 of differ- 

 ence to 



theoretical 

 radius. 



I. 



Mercury ... 



2 





2 



3-87 



+ 1-87 



+•935 



II. 



Venus 



Earth 



Mars 



Juno 



2 

 2 

 2 

 2 



+2 



+2x 3 

 +2X 6 

 +2x12 



4 



8 



14 



26 



723 

 10 



15-24 

 26-70 



+ 3-23 

 + 2 00 

 + 1-24 

 + 70 



+•807 

 +•200 

 +•089 

 +•027 



III. 



Jupiter 



Saturn 



Uranus 



Neptune ... 



2 

 2 

 2 

 2 



+24 

 +24 

 +24 

 +24 



+24 



+24 x 3 

 +24 x 6 

 +24x12 



50 



98 



170 



314 



5202 



95-39 



191-82 



300-37 



+ 2-02 

 - 2-61 



+21-82 

 -13-63 



+ •040 

 - 027 

 +•128 

 -•043* 





LXVII. The Theory of Double Refraction on the Undulatory 

 Hypothesis of Light. By Professor Challis, M.A., F.R.S., 

 F.R.A.S.f 



THE phenomena of light, viewed with reference to the hypo- 

 thesis of undulations, range themselves naturally in two 

 classes — those which depend only on properties and motions of 

 the medium in which the light is generated and transmitted, and 

 on its immediate action on the organ of sight, and those which 

 in addition depend on particular relations of the motions and dy- 

 namical action of the medium to visible and tangible substances. 

 In an article in the Philosophical Magazine for December 1862, 

 I have given explanations of various phenomena of the first 

 class, by referring them to laws and properties, mathematically 

 investigated, of the small undulations of an elastic fluid the 

 pressure of which is proportional to the density. I propose now 

 to enter upon the consideration of a phenomenon of the second 

 class, that of Double Refraction in crystals. The theory of such 

 a phenomenon necessarily rests on hypotheses respecting the qua- 

 lities and constituency of the refracting medium, as well as on 

 those relating to the sether. In the adoption of both kinds of 

 hypotheses, the ultimate conceptions respecting matter and force, 

 for which a priori reasons were given in my article in the Octo- 

 ber Number, will be strictly adhered to. In fact the pheno- 



* Astronomers appear still uncertain whether the distance of Neptune 

 from the Sun is not somewhat greater than that here attributed to it. If 

 it be, the relation of position indicated here may require to be diminished. 

 But even if it were converted from — into +, the theory would not be 

 affected. The result would show only that in the case of Neptune, as in 

 that of Uranus, the movement from the centre had predominated over that 

 to the centre. 



t Communicated by the Author. 



