If A and B were two houses at the top of the street, the street would seem to be as wide as the line A B:
And if C and D were two houses at the bottom of the street, the street at the bottom would seem to be no wider than E F.
Q. In an avenue of trees, why do they seem to be smaller as their distance increases?
A. Because the further the trees are off, the more acute will be the angle made by their perpendicular height with our eye.
Here the first tree A B will appear the height of the line A B; but the last tree C D will appear only as high as the line E F.
Q. In a long straight street, why do the houses seem to be smaller and smaller the further they are off?
A. Because the further any house is off, the more acute will be the angle made by its perpendicular height with our eye.
Thus in the last figure—