244 



Intelligence and Miscellaneom Articles. 



planes of polarization belongs an 

 infinite number of directions of 

 vibration. The directions are 

 perpendicular to each plane. 



4. The direction of vibration 

 of the extraordinary ray is per- 

 pendicular to its plane. There 

 is but one such direction ; it is 

 parallel to the axis. 



5. A colour B, that is a wave- 

 length, is in all azimuths united 

 to one direction of vibration. 



6. To one plane of polariza- 

 tion belongs one direction of vi- 

 bration. 



(2.) Observation. — In the vertical zones whose edges are perpen- 

 dicular to the axis of the crystal, in all azimuths, the ordinary ray 

 is polarized in the direction of the axis with the colour A. The ex- 

 traordinary ray is polarized perpendicular to the axis, and goes from 

 the direction of the observation, beginning perpendicular to the axis, 

 to the direction of the axis itself, passing from the colour B to the 

 colour A. Observed in the direction of the axis, the colours of both 

 rays perpendicular to each other are perfectly similar in all azimuths, 

 and possess the tone A. 



Consequences and Hypotheses as above. 



planes of polarization belongs 

 but one direction of vibration. 



4. The direction of vibration 

 of the extraordinary ray lies in 

 the plane of polarization. There 

 is an infinite number of such di- 

 rections. They lie in all azi- 

 muths perpendicular to the axis. 



5. A colour B is united to an 

 infinite number of directions of 

 vibration, one in each azimuth. 



6. To one plane of polariza- 

 tion belongs an infinite number 

 of directions of vibration. 



7. The direction of vibration 

 of the ordinary ray is perpendi- 

 cular to its plane. There is but 

 one such directionfor everyplane. 

 It is perpendicular to the axis. 



8. To one colour or wave- 

 length belongs but one direction 

 of vibration. 



9. The direction of vibration 

 of the extraordinary ray is per- 

 pendicular to its plane of polari- 

 zation. There is in every prin- 

 cipal section an infinite number 

 of such directions between 0° 

 parallel to the axis and 90° per- 

 pendicular to the axis. 



10. To the succession of co- 

 lours or wave-lengths from B to 

 A belongs an infinite number of 

 directions of vibration inclined 

 from 0° to 90°. 



7. The direction of vibration 

 of the ordinary ray lies in its 

 plane. There is an infinite num- 

 ber of such directions for every 

 plane. They include with the 

 axis all possible angles fi"om 0° 

 to 90°. 



8. To one colour or wave- 

 length belongs an -infinite num- 

 ber of directions of vibration. 



9. The direction of vibration 

 of the extraordinary ray is in its 

 plane of polarization. There is 

 for every principal section only 

 one such direction. It is per- 

 pendicular to the axis. 



10. To the whole series of co- 

 lours from B to A belongs, not- 

 withstanding the different wave- 

 lengths, but a single direction of 

 vibration. 



