As to the characteristic effects incident to the interception-bands; in Fig. 7 (Plate V.), let A’C’ represent at a given moment M, the total circumference of a color-disc, A’B’ represent a green sector of 90 deg., and B’C’ a red complementary sector of 270 deg..  If the disc is supposed to rotate from left to right, it is clear that a moment previous to M the two sectors and their intersection B will have occupied a position slightly to the left.  If distance perpendicularly above A’C’ is conceived to represent time previous to M, the corresponding previous positions of the sectors will be represented by the oblique bands of the figure.  The narrow bands (GG, GG) are the loci of the successive positions of the green sector; the broader bands (RR, RR), of the red sector.

In the figure, 0.25 mm. vertically = the unit of time = 1[sigma].  The successive stimulations given to the retina by the disc A’C’, say at a point A’, during the interval preceding the moment M will be

green 10[sigma], red 30[sigma], green 10[sigma], red 30[sigma], etc.

Now a certain number of these stimulations which immediately precede M will determine the characteristic effect, the fusion color, for the point A’ at the moment M.  We do not know the number of unit-stimulations which contribute to this characteristic effect, nor do we need to, but it will be a constant, and can be represented by a distance x = A’A above the line A’C’.  Then A’A will represent the total stimulus which determines the characteristic effect at A’.  Stimuli earlier than A are no longer represented in the after-image. AC is parallel to A’C’, and the characteristic effect for any point is found by drawing the perpendicular at that point between the two lines A’C and AC.

Just as the movement of the disc, so can that of the concealing pendulum be represented.  The only difference is that the pendulum is narrower, and moves more slowly.  The slower rate is represented by a steeper locus-band, PP’, than those of the swifter sectors.

We are now able to consider geometrically deduced bands as ‘characteristic effects,’ and we have a graphic representation of the color-deduction determined by the interception of the pendulum.  The deduction-value of the pendulum is the distance (xy) which it intercepts on a line drawn perpendicular to A’C’.

Lines drawn perpendicular to A’C’ through the points of intersection of the locus-band of the pendulum with those of the sectors will give a ‘plot’ on A’C’ of the deduction-bands.  Thus from 1 to 2 the deduction is red and the band green; from 2 to 3 the deduction is decreasingly red and increasingly green, a transition-band; from 3 to 4 the deduction is green and the band red; and so forth.