known impressions — unknown, because not attended to; but yet in some inexplicable way a part of our consciousness, since an effort of attention serves to bring them, any one of them, clearly into mental vision. At this instant you are looking at something. Now, without moving your eyes, try, by merely attending to your visual impressions, to say what is now in the field of vision, and where is the boundary line of the field of vision. The experiment is a little hard, because our eyes, condensed embodiments as they are of tireless curiosity, are always restless, and rebel when you try to hold them fast. But conquer them for an instant, and watch the result. As your attention roams about the artificially fixed visual field, you will at first, indeed, be confused by the vagueness of all but the centre; but soon you will find, to your surprise, that there are more different impressions in the field than you at first can distinguish. One after another, many various impressions will appear. But notice: you can keep your attention fixed on only a portion of the field at a time. The rest of the field is always lost in a dim haze. You must be receiving impressions all the time from all points of the field. But all of these, except the few to which you pay attention, nearly or quite disappear in the dim thickets that seem to surround the little forest-clearing made by our attentive consciousness. A like experiment can be tried with the sense of hearing, when you are in a large room full of people who are talking all around you in many independent groups. A mass of sound comes to your ear. Consciousness interferes to make
