TO finish his talk on lightning, the next morning Uncle Paul told them about clouds. The occasion, moreover, was very favorable. In one part of the sky great white clouds like mountains of cotton were piled up. The eye was delighted with the soft outlines of that celestial wadding. “You remember,” he began, “all those fogs that on damp autumn and winter mornings cover the earth with a veil of gray smoke, hide the sun, and prevent our seeing a few steps in front of us!” “Looking into the air, you could see something like fine dust of water floating,” said Claire; and Jules added: “We played hide and seek with Emile in that kind of damp smoke. We could not see each other a few steps away.” “Well,” resumed Uncle Paul, “clouds and fog are the same thing; only fog spreads about us and shows for what it is, gray, damp, cold; while clouds keep more or less above us and take on, with distance, a rich appearance. There are some of dazzling whiteness, like those you see over there; others of a red color, or golden-hued, or like fire; still others of the color of ashes, and others that are black. The color changes, too, from moment to moment. At sunset you will see a cloud begin with being white, then turn scarlet, then shine like a pile of embers, or like a lake of melted gold, and finally become dull and turn gray or black, according as the sun’s rays strike it less and less. All that is a matter of illumination by the sun. In reality, clouds, however splendid in appearance, are formed of a damp vapor like that of fog. We can assure ourselves of this by a near approach.” “People can then mount as high as the clouds, Uncle?” Emile asked. “Certainly. All one needs is a pair of legs stout enough to climb to the top of a mountain. Often then clouds are under one’s feet.” “And you have seen clouds underneath you?” “Sometimes.” “That must be a very beautiful sight.” “So beautiful that words cannot express it. But it is not exactly a pleasure if the clouds mount and envelop you. You can be very much embarrassed by the obscurity of the fog alone. You lose your way; you become confused, without suspecting any danger in the most dangerous places, at the risk of falling into some abyss; you lose sight of the guides, who alone know the way and could save you from a false step. No, all is not roses up among the clouds. You will perhaps learn that some day to your cost. Meanwhile let us transport ourselves in imagination to the top of a cloud-capped mountain. If circumstances are favorable, here is what we shall see: