that no one else thought much about. One day he saw a sunbeam shining through a round hole in a shutter into a dark room. The beam made a golden road to the opposite wall. There it ended in a spot of light. When Newton saw this, he thought:
"I wonder what would happen if I were to catch that sunbeam, and make it pass through this triangular bar of glass?"
Light goes right through a pane of glass, you know. But because of the unequal thickness of the triangle or prism, the beam went through it in a curious way The ray went to the middle of the prism straight and white. There it was bent at the angle of the prism's sides and spread out like a fan. The round spot on the wall was gone. In its place was a narrow panel, in seven color bands like a thin slice cut across a rainbow. And the colors were arranged in the same order as in a rainbow—red, orange, yellow, green, blue and violet.
Why do you suppose he called this a spectrum? Specter means an image of light, a heavenly vision. He stood in wonder and awe at the unearthly beauty of those color bands of light. And he hoped that he had found a key of light to unlock some of the secrets of the far-away sun and stars. Newton caught starbeams and rays from white hot iron. And he tried the effect of burning the dust of lime, salt, iron and other minerals. He discovered that when salt (sodium) was burned the yellow band of the spectrum came out very bright.
When you boys and girls are hunting a hidden object you know. what it is to get "warm." Newton and other scientists who experimented with the spectrum, knew they were "warm," or very close to the secret of yellow when sodium, and nothing else in nature, always made the yellow band blaze brighter. In this way they determined that there is sodium in the sun and the stars, just as there is in our own earth. You see the key of light began to turn in the lock. After long experimenting it was discovered just what element makes each and every color. Everything that was found by the spectrum to exist in our world was found to exist in others. The spectrum revealed not only the materials of other worlds and furnished a test by which the elements could be detected, but it proved the laws by which light is governed. Across the color bands of the spectrum are many dark lines in which no light or color appears. These are caused by light rays crossing and putting each other out. The only way in which they can do this is by travelling in waves or ripples, just as air and water and sound travel.
