Thoreau writes in his journal:
In my ride I experienced the pleasure of coming into a landscape where there was more distance and a bluish tinge in the horizon. I am not contented long with such narrow valleys that all is greenness in them. I wish to see the earth translated, the green passing into blue. How this heaven intervenes and tinges our more distant prospects! The farther off the mountain which is the goal of our enterprise, the more of heaven’s tint it wears . . .