swings past the middle point of _I_ in 275[sigma].

Now when the eye moves it must move at this rate. If the eye is 56 cm.
distant from the opening, as in the previous case, the 9 cm. of
exposure are 9° 11' of eye-movement, and we saw above that 9° 11' in
110[sigma] is a very slow rate of movement, according to the best
measurements. Now it is impossible for the eye to move so slowly as 9°
11' in 275[sigma]. If, however, the eye is brought nearer to the
opening, it is clear that the 9 cm. of exposure become more than 9°
11' of eye-movement. Therefore the eye and the fixation-points are so
placed that _EA_ (Fig. 5) = 26 cm. and _PP'_ = 18 cm. The total
eye-movement is thus 38° 11', of which the nine-centimeter distance of
exposure is 19° 38'. Now the eye is found to move very well through
19° 38' in 275[sigma], although, again, this is much more than a
proportionate part of the total time (99.9[sigma]) given by Dodge and
Cline for a movement of the eye through 40°. The eye is in this case
also moving slowly. As before, it is permissible to let the pendulum
run down till it swings too slowly for the eye to move with it; since
any lessened speed of the pendulum only makes the reddish-orange phase
more prominent.

As in the experiment with the dumb-bell, we have also here three
cases: the control, the case of the eye moving, and again a control.

Case 1. _T_ swings with the pendulum. _I_ is placed in the front
groove, and the eye looks straight forward without moving. The
pendulum falls from 9.5° at one side, and the illumination is so
adjusted that the phase in which the band is reddish-orange, is
_unmistakably_ perceived before that in which it is straw-yellow. The
appearance must be 3 followed by 5 (Fig. 8).