In other directions the polarization becomes less and less complete as we approach the vertical.
Closely associated with the colour is the polarization of the light from the sky.
On the other hand, that the direction of complete polarization should be independent of the refracting power of the matter composing the cloud has been considered mysterious.
This reverse electromotive force of polarization is produced in all electrolytes when the passage of the current changes the nature of the electrodes.
After an interval the polarization begins to be incomplete in the perpendicular direction, the light which reaches the eye when the nicol is set to minimum transmission being of a beautiful blue, much richer than anything that can be seen in the earlier stages.