What a jumble of lines there is in [Fig. 8], something like a spider’s web, and one can make nothing out of it. But lift the book up, as in the last example, and close one eye—the letters are plain enough, are they not? You have played a trick on your own eye, and made its habit of shortening lines serve to interpret a message that would otherwise be unintelligible.
Fig. 7.—The standing pins.
Fig. 8.—“Yes or no?”
The Stars don’t Twinkle
Every cloudless night the eyes make a mistake that we can easily discover, but which we are totally unable to remedy.
Of course you have looked up to the sky thousands of times and seen the stars twinkling. Not only that, but if the night is clear you can see they are stellate, or star-shaped, like the starfish which is named after them. You can see both of these things, and yet the strange fact is that neither of them is true!
The stars do not twinkle at all, and they are not stellate. The twinkling is the result of the intervening atmosphere, and not the fault of our eyes; but the second error can be easily brought home to our untrustworthy organs of vision by the following experiment.
