In any case it is highly probable that whenever the eye did not move at just the rate of the pendulum, it moved more rapidly rather than more slowly.  The image is thus horizontally elongated, by an amount which varies from the least possible up to 9 cm. (the width of the opening in T), or even more.  And while the last of the movement (O to P, or N to P’), in which the stimulation of H’ is supposed to subside, is indeed executed, it may yet be done so rapidly that after all H’ cannot subside, not even although it is now less intense by being horizontally spread out (that is, less concentrated than the vanished h of shape 4).  This explanation is rendered more probable by the very rare appearance of shape 5, which must certainly emerge if ever the eye were to move more slowly than the pendulum.

The critical fact is, however, that shape 4 does appear to a trained subject in about one half the trials—­a very satisfactory ratio when one considers the difficulty of timing the beginning of the movement and its rate exactly to the pendulum.

Lastly, in some cases no image appears at all.  This was at first a source of perplexity, until it was discovered that the image of the dumb-bell, made specially small so as to be contained within the area of distinct vision, could also be contained on the blind-spot.  With the pendulum at rest the eye could be so fixed as to see not even the slight halo which diffuses in the eye and seems to lie about the dumb-bell.  It may well occur, then, that in a movement the image happens to fall on the blind-spot and not on the fovea.  That this accounts for the cases where no image appears, is proved by the fact that if both eyes are used, some image is always seen.  A binocular image under normal convergence can of course not fall on both blind-spots.  It may be further said that the shape 4 appears as well when both eyes are used as with only one.  The experiment may indeed as well be carried on with both eyes.

Some objections must be answered.  It may be said that the image of h happens to fall on the blind-spot, e and e being above and below the same.  This is impossible, since the entire image and its halo as well may lie within the blind-spot.  If now h is to be on the blind-spot, at least one of the end-circles e, e will be there also, whereas shape 4 shows both end-circles of the dumb-bell with perfect distinctness.

Again, it cannot properly be urged that during the movement the attention was distracted so as not to ‘notice’ the handle.  The shape of a dumb-bell was specially chosen for the image so that the weaker part of the stimulation should lie between two points which should be clearly noticed.  Indeed, if anything, one might expect this central, connecting link in the image to be apperceptively filled in, even when it did not come to consciousness as immediate sensation.  And it remains to ask what it is which should distract the attention.