subject is a huntsman galloping over the countryside with a dog at the horse's heels. Every action of the one animal is somewhat like every corresponding action of the other animal. One might even say that the horse is a large kind of dog, while the dog is a small kind of horse. And, as they cross the fields in loyalty to the same master, their motions harmonize.
There would be unity of a similar kind in a picture of an automobile and a railroad train racing on parallel roads. Although they are two separate machines, their motions fuse into one thing, which we call a race. If the roads are not perfectly parallel but swing slowly away from and toward each other again, we get a pleasing rhythm of motions, yet, because the directions and speeds are similar, the unity still remains.
But if we imagine the train dashing by a farmstead where a Dutch windmill sweeps its large arms slowly around, we would feel again a lack of unity between the two kinds of motions. The impression upon our minds would be confused; it would not be a single impression, because the moving objects show two different kinds of patterns, with rates of speed that are not sufficiently alike to be grasped as a unity. A better picture would be that of an old Dutch mill on the bank of a river whose sluggish waters flow wearily by. Perhaps even an old steamboat with a large paddle wheel might be so introduced that the revolutions and patterns of the two wheels would be similar, while the forward thrusts of the boat and the current would also be similar, all four movements blending together into a single harmony, like the music of four different instruments in an orchestra.
