436 



WRIGHT— POLARIZED LIGHT IN THE 



of glass plate =1.515). The two curves do not coincide; no satis- 

 factory explanation for the discrepancy has yet been found. 



Photometrically the gradation in intensity between the different 

 Savart bands is less advantageous than the juxtaposition of two or 

 a series of evenly illuminated fields, the one at minimum intensity 

 the next at maximum intensity. This principle is used in measure- 

 ments of sky polarization and can be readily applied to the present 

 problem. 



Fig. 9. Curve illustrating tlie percentage intensity ratio (ordinates) be- 

 tween the two components, normal and parallel to the plane of incidence, of 

 light transmitted through a tilted glass plate for different angles of rotation 

 (abscissae). 



Nezv Method. — For this method use is made of a cleavage plate 

 of calcite of such thickness and an aperture of such width that the 

 two fields from the two rays just touch (Fig. 10) ; better fields are 

 obtained by use of a small Koenig-]\Iartens portable photometer" 

 (Fig. II). 



3 Verhandlungen d. dcutsch. Physikal. Gesellschaft, i, 204-208, 1899 ; 

 Physikalische Zeitschrift, i, 299-303, 1900. 



