1 2 3 4 5 a b a b a b a b a b I. 0 0 0 0 0 0 0 0 0 0 II. 43 41 33 51 19 31 32 41 20 18 III. 0 6 0 0 3 11 13 16 0 0 IV. 56 28 23 35 0 11 48 56 35 25 V. 56 55 44 44 57 30 39 32 34 30 VI. 14 8 12 12 11 5 35 12 9 6 VII. 52 54 56 56 51 47 56 57 47 26 VIII. 15 0 18 21 24 39 26 10 23 21 IX. 28 25 39 31 23 28 26 36 25 17 X. 0 0 0 0 0 0 0 0 0 0 XI. 52 45 41 48 7 39 50 36 48 22 35.11 29.11 29.55 33.11 21.66 26.78 29.55 26.91 21.91 15.00 _Series No. XVI._--The course of experimentation having shown the superior energy of lines, in comparison with surfaces, in stimulating, directing, and holding the attention, a series of figures was devised to test the question whether the direction of the lines would have any effect upon the length of time during which _both_ images of a pair of linear figures would be presented together. The materials used were granite-gray strips half a centimeter wide. The letters (_a_) and (_b_) at the heads of the columns refer to the same letters in the diagram, and distinguish the different arrangements of the same pair of objects. The figures in the body of the columns show only the length of time during which both images were reported present in consciousness together. At the foot of the columns are shown the averages for each pair. No general averages are shown, as the problem presented by each pair is peculiar to itself. [Illustration: FIG. 7.]