384 Sir David Brewster on the Compensations of Polarized Light. 



sation takes place about 70°, it will also take place about 40°, and these angles 

 will afford measures of the degree of polarization necessary to produce the com- 

 pensation required. 



In order to make these observations at different inclinations to the horizon, 

 the pillar which carries the graduated circle of the goniometer, and also the 

 pillar GH, must move upon a joint, as shewn in Fig. 2. By observations such as 

 those above described, the following angles of compensation will be obtained : 



Compensations between two Reflexions, one above and one below the polarizing 



Angle. 



Compensations between one Reflexion below the polarizing Angle, and one 



Refraction. 



Reflexion. Refraction. 



2° 10° 



5 22 



10 42 



15 59 



20 74 



24 80 



25 81 

 28 87 

 30 89^ 



