685 



4i 

 5 



6 



6i 



7 



n 



8 



lioiirs 



A = C_C„ 



l TT. 



ü O • rn I I 



20 



l5 



O & 



-H^ 



. ' 



<^ 



/i>l_^ 



i\^x 



'-y^T 



o. 'o o 



7-'— h 



A.25.25r°'°?^^ 



time 



in 

 hours 



Fig. 1. 



When if is borne in mind, that the error in the readings of 

 the compensator amounts to 0.03, the agreement of the observations 

 with the curves traced may be considered as very satisfactory. As 

 according to ^ 4 a displacement of 14.34 of tlie movable compensator 

 wedge corresponds to a difference of phase of :t in circular measure, 

 c^-c, denotes a difference of phase of 0.25 : 28.68 = 0.0087. In 

 the following way the change in the angle of principal incidence /, 

 corresponding with this, could be obtained. 



