For the same reason, of two squares absolutely identical in size, one marked with alternately clear and dark cross-bands, and the other with alternately clear and dark upright markings, the former will appear broader and the latter higher than the other.
Experiment 183. Make on a white card two squares of equal size. Across the one draw horizontal lines at equal distances, and in the other make similar vertical lines. Hold them at some distance. The one with horizontal lines appears higher than it really is, while the one with vertical lines appears broader, i.e., both appear oblong.
Experiment 184. Look at the row of letters (S) and figures (8). To some the upper halves of the letters and figures may appear to be of the same size as the lower halves, to others the lower halves may appear larger. Hold the figure upside down, and observe that there is a considerable difference between the two, the lower halves being considerably larger.
S S S S S S S S 8 8 8 8 8 8 8 8
Experiment 185. To illustrate imperfect visual judgment. The length of a line appears to vary according to the angle and direction of certain other lines in relation to it ([Fig. 147]). The length of the two vertical lines is the same, yet B appears much longer than A.
Fig. 147.—To show False Estimate of Size.