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Page:Popular Science Monthly Volume 4.djvu/686

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things, and construct a symbolic idea which represents our planet, but we never grasp the reality in the immensity of its proportions.

Light is a force, and science holds that it is made up of impulses. Nature has been shown to conform all kinds of dynâmical effects to rhythmical pulsing, or wave-like action and the impulses of light are held to be of the same kind. There are, at any rate, measurable effects which are unequal in the different colored lights, and the scale has been determined. In an inch of violet light it is shown that there are no less than 57,000 waves, a statement in which there is nothing extraordinary or impossible, as Nobert, the German optician, is in the habit of ruling his microscopical test-glasses at rates all the way from 100,000 to 200,000 per inch. But, when we are told that the ray enters the eye at the rate of 185,000 miles per second, and—as each inch contains 57,000 waves—that when we are looking at a violet object there are 699,000,000,000,000 beats upon the retina each second, the statement baffles all imagination: we may accept, but cannot understand it. In the attempt to penetrate the nature of light we are lost in the mysteries of the infinite. Yet the modes of its action have been determined, and they furnish the most splendid example we know of the inflexibleness and exactitude of what are called the laws of Nature.

Fig. 2.
PSM V04 D686 Image formed by hole in a card.jpg
Image formed by a Hole in a Card.

Man is placed in the midst of the universe, and is designed to have knowledge of it. He is impressible to outward agencies, and possesses a grand cerebral treasury-house for storing up these external impres-