Can you find another perfect solution?
No. IV.—AN ILLUSION OF MOTION
We call very particular attention to this fascinating illustration of the fact that the mind and eye may receive and register false impressions under quite simple conditions:—
Hold this at rather more than reading distance, upright, and move it steadily up and down. The dark line will soon seem to slide up and down upon the perpendicular line. It will be better seen if drawn to pattern on a card.
No. V.—ARE THEY PARALLEL?
As the eye falls upon the principal lines of this interesting diagram, an immediate impression is formed that they are not parallel.
This, however, is a most curious illusion, created in the mind entirely by the short sloping lines, as is found at once by the simple test of measurement.