Page:Mind (Old Series) Volume 12.djvu/538

 THE PEKCEPTION OF SPACE. (IV.) 525 told me it soon became difficult to see how to apply the brush. Bend a visiting card across the middle, so that its halves form an angle of 90 more or less ; set it upright on the table, as in Fig. 17, and view it with one eye. You can Fig. 17. make it appear either as if it opened towards you or away from you. In the former case, the angle rib lies upon the table, ~b being nearer to you than a ; in the latter case ab seems vertical to the table as indeed it really is 1 with a nearer to you than 6. Again, look, with either one or two eyes, at the opening of a wine-glass or tumbler (Fig. 18), held either above or below the eye's level. The retinal image of Fia 18. 1 Cp. E. Mach, Beitrage zur Analyse der Empfindungen, p. 87.