As to the first. Suppose you are standing on a street or country road, and a wagon passes you. While it is close in front of you, the body of the wagon and the wheels and the man driving, all are clearly outlined; you can distinguish distinctly the parts of the wagon and the character of the man’s figure, whether it is fat or thin, strong or weak-looking, and so on. But, as the wagon passes along the road, its appearance changes. At first, it is the smaller details that disappear; they have become merged in the general mass; then the outlines of this mass grow less and less distinct; you could not be sure now, unless you had seen the wagon close, exactly what its build is; nor does one part seem nearer to you than another, its bulk has become flattened, and gradually the whole affair looks to be only a patch of color against the color of the road.