Optical Illusion: Inclined Letters

When looking at the accompanying sketch you will say that the letters are alternately inclined to the right and left.

Optical Illusion: Inclined Letters

They are not so and can be proved by measuring the distance of the top and bottom of any vertical strokes from the edge of the entire block. They will be found to be exactly the same distance. Or take any of the horizontal strokes of the four letters and see how far their extremities are from the top and bottom of the entire block. It will be found that a line joining the extremities of the strokes are strictly parallel to the top or bottom and that they are not on a slant at all. It is the slant of the numerous short lines that go to make up the letter as a whole that deceives the eye.

Source: Project Gutenberg’s The Boy Mechanic: Volume 1, by Popular Mechanics, Produced by Don Kostuch