In the colours adjoining these - indigo and violet on the blue side, orange and red on the yellow side - Goethe recognized 'heightened' modifications of blue and yellow. Thus he had learnt from the macro-telluric realm that with decreasing density of the corporeal medium, the blue sky takes on ever deeper tones, while with increasing density of the medium, the yellow of the sunlight passes over into orange and finally red. Prismatic phenomenon and macrotelluric phenomenon were seen to correspond in this direction, too.