800 Mr. J. Crosby Chapman on some 



Combining this result with others obtained : — 



Table IX. 



Polarization of direct 

 secondary beam. 



Polarization of secondary 

 beam after transmission 

 through sugar solution. 



3-5 

 3-6 

 3-4 

 34 

 3-4 



35 

 37 

 33 

 3-4 

 3-6 



Mean value . 3 - 5 



3j 



These results clearly prove that no measurable rotation of 

 the plane of polarization of X-rays is produced by a sugar 

 solution which is active for light in the visible spectrum. 



The interpretation of these results is not that a fundamental 

 difference exists between X-rays and light, but the experi- 

 ments rather indicate that the usual formulae which determine 

 the relation between rotation and wave-length for light in 

 the visible spectrum are quite inadequate when light of 

 exceptionally short wave-length is concerned. 



Absorption of polarized X-rays by Iron in Magnetized State. 



It is legitimate to assume that the absorption of X-rays by 

 an atom of any given substance must depend to a certain 

 extent on two factors : — (1) the period of the X-radiation 

 absorbed ; (2) the natural period of vibration of the electrons 

 within the atom. 



In order to explain double refraction and other phenomena 

 peculiar to crystalline substances, it is necessary to suppose 

 that the period of vibration of the electrons is dependent on 

 the direction of vibration with respect to the atomic system. 



Now in a polarized beam of X-rays, the electrical vibrations 

 are largely in one direction. Consider now such a beam 

 being transmitted through iron in which, since it is un- 

 magnetized, there is no regular orientation of the orbits of 

 the electron in the system. If, now, the iron is magnetized, 

 the orientation becomes more regular, and if absorption of 

 X-radiation is dependent on the direction of its own electrical 

 vibration relatively to that of rotation of the electron in the 



