But here they take two hundred thousand tall forest trees and set them in a double row; allow no sign of leaf or branch to grow on the trunk lower down than six feet above the ground; from that point the boughs begin to project, and very gradually they extend outward further and further till they meet overhead, and a faultless tunnel of foliage is formed.

The arch is mathematically precise.

The effect is then very fine.

They make trees take fifty different shapes, and so these quaint effects are infinitely varied and picturesque.

The trees in no two avenues are shaped alike, and consequently the eye is not fatigued with anything in the nature of monotonous uniformity.