404) M. Rudberg on the Dispersion of Light. 



A similar calculation for the same flint-glass, and the crown- 

 glass, No. 13, gives the following values of r: 

 According to the rays 



B and C : 7- = 1-8718 I B and F : r = 1-9140 



B and D:r = 1-8970 B and G :;•= 1-94.75 



B and E : r = 1-9090 j B and H: r = 1-9748 



Mean value r = 1-919. 



And calculating by the formula N = N' ( -r^ 

 we have for the indices of flint-glass the following values : 

 C = 1-6298 F = 1-6483 



D = 1-6351 

 E = 1-6421 



G = 1-6598 

 H = 1-6698 



Also in comparing, finally, the flint-glass, No. 13, with the 

 crown-glass, Lett. M, we find the subjoined values of r : 

 According to the rays 



Mean value r = 1 -609. 

 And calculating the indices of flint-glass by the formula : 



N = N' (-^) we obtain : 



C = 1-6297 

 D = 1-6351 

 E = 1-6419 



F = 1-6480 

 G= 1-6595 

 H= 1-6697 



Supplernent. 

 If we calculate the indices of refraction of flint-glass, No. 13, 

 according to the formula : 



N = 1-6277 (irT' 



in which the exponent [2*6 is such, that it belongs to the rays 

 B, and the rays H, in flint-glass and in water, which rays, 

 being the most distant from each other, afford the most certain 

 result, we have the second column of the following table : 



In returning from flint-glass. No. 1 3, to water, and calcu- 

 lating the indices of water according to the formula : 



n = 1-3309 (-^)°-" 



We. 



