M. Rudberg on the Dispersion of Light. 405 



We find 



Observation. Calculation. Observation. Calculation. 



B 1-3309 F 1-3378 1-3374 



C 1-3317 1-331.3 G 1-34.12 1-3412 



D 1-3335 1-3333 H 1 '344.1 1-3446 



E 1-3358 1-3354 



In comparing flint-glass, No. 1 3, and oil of turpentine, the 

 values of r are, 



According to the rays 

 B and C : r = 1-806 

 Band D:r = 1-689 

 B and E : r = 1-653 



B and F : r = 1-649 

 B and G : r = 1-657 

 B and H: r = 1-670 



And calculating the indices of flint-glass, according to the 



formula 



We have 



Observation. 

 B 1-6277 

 C 1-6297 

 D 1-6350 

 E 1-6420 



N = 1-6277 



G) 



1-67 



Calculation. 



1-6295 

 1-6349 

 1-6421 



Observation. 

 F 1-6482 

 G 1-6602 

 H 1-6710 



Calculation. 

 1-6481 

 1-6605 

 1-6710 



In comparing flint-glass, No. 13, with flint-glass. No. 3, 

 have the following values of r : 

 According to the rays 



B and C :?• = 1-093 



B and D:r = 1-105 



B and Err = 1-125 



And calculating the indices of flint-glass. No. 1 3, according 



And calculating the indices of flint-glass. No. 13, according 

 to the formula N = 1-6277 (—)'"' 



We 



