Aerial perspective of mountains; how the 'chain of the world' forms
Why air among peaks turns blue and is brightest toward the sun, with a diagram of eye, valley p and peak a
A page of the Treatise on Painting on the aerial perspective of mountains: the intervening air makes distant peaks appear blue, and is more luminous toward the side of the sun than in the opposite parts. A pen diagram of a mountain profile, labelled with the valley p and the peak a, has converging lines meeting at the eye (occhio) to the right, illustrating why the air reads clearer over the valley p than over the peak a. A final chapter turns to how mountain forms, 'the chain of the world', are generated by river courses fed by rain, snow, hail and ice melted by the summer sun.
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Why mountain air looks blue and brightest toward the sun
Through the clarity of the intervening air distant mountains come to appear blue to the eye. The air shows itself more luminous and clear toward the side of the sun than in the parts opposite to it.
The air reads clearer over the valley p than over the peak a
The air interposed between the eye and the mountain appears clearer at p than at a. First, the air between the eye and p is a greater amount and so clearer; second, the air is thicker at the valley p than at the mountain a. A profile diagram carries the labels p and a with lines running to the eye at the right.
Mountains, the 'chain of the world', generated by rivers
The forms of the mountains, called the chain of the world, are generated by the courses of rivers born of rain, snow, hail and ice melted by the sun's rays of summer. That melting gathers waters from many small streams converging into greater ones, which grow in magnitude as they run.