"All those old rhymes are fakes, though, Dan'l," declared Anton, with the importance of his newly acquired weather knowledge. "Easy there, easy there!" warned the Forecaster. "Not so fast. A good many of those old rhymes are mighty good weather forecasts. That one is, for example." "You mean, sir, that a red sunset and a gray sunrise really tell that the weather is going to be fine?" "Yes, to a great extent, they do." "Why, Mr. Levin?" "Because they show the state of the atmosphere, boys. Rain can't fall unless there is dust. Every little drop of rain has a grain of dust in the middle. The colors of the sunset, too, are due partly to dust. Not only that, but colors of the sunset vary as the particles of dust which reflect the rays of light, are enveloped by water vapor. "A piece of dust, without an envelope of water, is smaller than one with a little wetness around it. When more water vapor gathers around the piece of dust, the drop becomes bigger. When the sunset is red, it is a sign that it is shining on very small bits of dust, or that the condensation of water vapor into rain has not advanced very far. If, however, the sunset sky is gray, that means that the upper air is saturated, that it has all the water it can hold, and, of course, rain is likely to come soon." "I should think, then," said Anton, "that gray in the morning would be a bad sign, too." "It's not, though," the Forecaster replied; "the proverb is right there, as well. A gray sky in the morning means that the air is filled with water drops which are large enough to reflect light of every color. While this is the same as the gray of evening, the processes that led to the forming of these drops is quite different. In the day the dust is heated and the forming of the droplets in the afternoon is due to cooling. In the night, the condensation is caused by loss of heat through radiation. Radiation shows that the air above must be dry. Therefore a gray morning means a dry air above the water drops, and this means a fine day, for the droplets will soon be evaporated by the rising sun. The red morning sky declares that the dust particles have been protected from radiation by a blanket of overlying moisture, the air, therefore, is saturated to great heights and rain is probable. So you see, Anton, Mammy's rhyme is right." "What fo' yo' talk to me against signs," declared Dan'l, putting out his chest and strutting; "Ah done told yo' them signs am pow'ful good." "But the sunset colors, sir?" the author of the article asked. "You said they were due to dust. Just how, sir?" "Yes, to dust, plain ordinary dust, but dust of the lightest kind," was the reply. "If you could go up in the air a hundred miles, the sky above you in the middle of the day would be jet black and the sun would shine down on you like a great bright-blue ball, without any white glare around it at all." "Then it's a blue sun that makes a blue sky!" cried Fred.