Rhythmical rows of beats, because of the arrangement of the successive impressions in them, were excellently suited to determine the total scope of consciousness. But because of this very same quality they can give us little help in solving our second problem. For it is obvious that just that connection between the focus of attention and the wider field of consciousness, that the rhythm of a row of beats causes--this connection makes a clear boundary between these two regions impossible. We notice clearly enough that along with the beat that is directly affecting consciousness a few of the preceding ones also fall within the focus of attention, but how many remains uncertain. The sense of sight obviously offers us more favourable conditions. We must, however, first of all note the fact that the physiological conditions of vision in themselves limit the apprehension of an extended object, not taking into account the psychological boundary of clear perception. The keenest differentiation of impressions is limited to the so-called region of clearest vision, which surrounds the fixation-point. The reader can test this for himself by fixating the middle letter "_o_" in the following diagram of letters from a distance of about 20-25 cm, while keeping one eye closed. We can in this position, by directing our attention alone to the outlying parts of the field of vision, still recognise letters, which lie at the sides of our figure, as, for example, the _h_ at the top or the _i_ at the right-hand side. To carry out this experiment a little practice in fixation is required, since in natural vision we are always inclined to direct our line of vision to that point, to which our attention is turned. If, however, we practise letting our attention wander over the different parts of the field of vision while keeping the same fixation-point, it will soon be clear to us that the fixation-point of attention and the fixation-point of the field of vision are by no means identical. They can by practice be separated, and the attention can be directed to a point in indirect vision, i.e. a point lying to this or to that side of the line of vision. From this we see that clear perception in the psychological sense and clear vision in the physiological sense do not necessarily coincide. For example, if we fixate the middle letter _o_, and at the same time direct our attention to the "_n_" at the right-hand side, we also perceive clearly the letters that surround _n_, i.e. _f g s i_, whereas the letters around _o_, i.e. _h t i n_, seem to retreat into the darker field of consciousness. This diagram of letters has been printed so large, that when we look at it from a distance of 20-25 cm. it almost corresponds in scope to the region of clearest vision, taking as a measure for this the recognisability of letters of the size of those printed in this book. We see, therefore, at once from the above-described