Experiments on Polarized Rontgen Radiation. 797 



would have been a decrease in the intensity of the horizontal 

 tertiary beam and a consequent increase in the intensity of 

 the vertical tertiary beam, resulting therefore in a con- 

 siderable decrease in the ratio which determines the 

 polarization. The fact that this ratio does not alter proves 

 that no appreciable rotation of the plane of polarization 

 takes place. 



Experiments on Quartz. 



The crystal used had to satisfy two conditions : firstly, it 

 had to be approximately of the area of the slit in the lead 

 screen at S 4 , and it had also to be thin enough to transmit 

 rays of the hardness used in the experiment. The quartz, a 

 right-handed crystal cut perpendicular to the optic axis, was 

 6*5 cm. in diameter, and of thickness 4 mm. 



The method of investigating its rotatory power for a beam 

 of polarized X-rays was very similar to that described in the 

 case of iron. In the first part of the experiment, the ratio 

 of the intensities of the tertiary beam reaching the electro- 

 scopes A x and A 2 was determined when the quartz was 

 absent. The quartz was then placed at XX, in the path 

 of the secondary beam, and the ratio which standardized 

 the polarization again determined. In the experiment the 

 quartz transmitted from 70 to 30 per cent., according to the 

 hardness oE the bulb. 



The full results are given in tabular form. 



Quartz. 

 Table IV. 



Condition of experiment. 



Deflexion of 

 electroscope 

 receiving hori- 

 zontal tertiary 

 beam. 



— — — — — - — — — 



Deflexion of 



electroscope 



receiving 



vertical tertiary 



beam. 



( (\) Carbon radiators "1 

 Direct R x + R 2 present . J 



^ ] (ii) Carbon radiator \ 



beam. R L present > 



^ R 2 absent J 



12-8 



7-5 



4-9 

 36 



( (i) Carbon radiators "1 

 Secondary beam | R x +R 2 present. J 



transmitted \ ,..-, *. , ,. , -, 

 J (n) Carbon radiator 



through quartz. | R t present ^ 



^ R 2 absent J 



11-8 



8-4 



45 

 37 



