The sun was well past its zenith and headed toward the trees on the west side of the cabin.
The colour usually deepens toward the zenith and also with the elevation of the observer.
The simple theory of the dispersion of light by small particles suffices to explain not only the blue of the zenith, but the comparative absence of small wave-lengths from the direct solar rays, and the brilliant orange and red coloration of the setting sun and of the clouds illuminated by his rays.
The normal polarization at the zenith, as dependent upon the position of the sun, was the foundation of Sir C. Wheatstone's polar clock.
These years mark the zenith of Athenian greatness.