Double Refraction in Carbon Disulphide 7 



equation (3), by the ratio of the order of the "compensator" 

 [ N= — — determined bv means of the quarter-wave plate for 



L 43SJ 



that particular value of A, which, in this case, was 560 //./a, while 

 the order for any other colors used was obtained by interpolating 

 from the curve obtained by Rendtorff. 



100 



200 



300 



P 



a < 10 



_40C 



soo 



In fig. 4 the values of i^Xio"'' are plotted as ordinates and 

 as abscissae. The curve is approximately a straight Ime 



until about 200 volts per millimeter of distance, when it turns 

 and seems to become almost asymptotic to the ordinates. On 

 obtaining these low values the errors of observation were of 

 course large, owing to the smallness of the effect, and at first it 

 was thought that the large deviation from the law was due to 

 some systematic error. To eliminate such possible errors, the 

 apparatus was taken down and remounted under different con- 



