Take again a living body of a seemingly uncomplicated kind—say a potato. Cut it through and observe how structureless is its substance. But though unaided vision gives this verdict, aided vision gives a widely different one. Aided vision discovers, in the first place, that the mass is everywhere permeated by vessels of complex formation. Further, that it is made up of innumerable units called cells, each of which has walls composed of several layers. Further still, that each cell contains a number of starch-grains. And yet still further, that each of these grains is formed of layer within layer, like the coats of an onion. So that where there appears perfect simplicity there is really complexity within complexity. From these examples which the objective world furnishes, let us turn to some examples furnished by the subjective world—some of our states of consciousness. Up to modern times any one who, looking out on the snow, was told that the impression of whiteness it gave him was composed of impressions such as those given by the rainbow, would have regarded his informant as a lunatic; as would even now the great mass of mankind. But since Newton’s day, it has become well known to a relatively small number that this is literal fact. Not only may white light be resolved by a prism into a number of brilliant colours, but, by an appropriate arrangement, these colours can be re-combined into white light: the visual sensation which seems perfectly simple proves to be highly compound. Those who {197} habitually suppose that things are what they seem, are wrong here as in multitudinous other cases. Another example is supplied by the sensation of sound. A solitary note struck on the piano, or a blast from a horn, yields through the ear a feeling which appears homogeneous; and the uninstructed are incredulous if told that it is an intricate combination of noises. In the first place, that which constitutes the more voluminous part of the tone is accompanied by a number of over-tones, producing what is known as its _timbre_: instead of one note, there are half a dozen notes, of which the chief has its character specialized by the others. In the second place, each of these notes, consisting objectively of a rapid series of aërial waves, produces subjectively a rapid series of impressions on the auditory nerve. Either by the appliance of Hooke or by Savart’s machine or by the siren, it is proved to demonstration that every musical sound is the product of successive units of sound, each in itself unmusical, which, as they succeed one another with increasing rapidity, produce a tone which progressively rises in pitch. Here again, then, under an apparent simplicity there is a double complexity.