“Certainly not: losing as much as it receives, it must always keep the same level.” “It is the same with the sea. It loses just as much as it gains, and therefore its level always remains the same. Brooks, torrents, streams, rivers, all run into the sea; but brooks, torrents, streams, and rivers also come from the sea. They carry back to the immense reservoir what they took from it, and not a drop more.” “If the crab brook comes from the sea,” interposed Emile, “as you say, its water ought to be salt; but I know very well it is not, in the least.” “Certainly it is not salt; but the brook does not come out of the sea as the water of a ditch comes from a reservoir. In coming from the sea, before becoming what it is, the brook has first passed through the air as clouds.” “As clouds?” “As clouds, my little friend. Let us recall something I told you a while ago. “The heat of the sun causes water to evaporate; it reduces it to something invisible, to vapor that is dissipated in the air. Seas present a surface three times that of the dry land. Over these immensities there is constantly taking place an enormous evaporation, raising into the air a part of the waters of the sea. The vapor thus formed becomes clouds; the clouds are borne in all directions, letting down snow and rain; this rain and melted snow penetrate the ground, filter down and give birth to springs, which gradually, by their union, become brooks, streams, and rivers.” “I see why the water of brooks is not salt,” said Jules, “although it comes from the sea. When you put salt water in a plate in the sun, only the water goes away; the salt remains. The vapor that rises from the sea is not salt, because the salt does not go with it when it forms. So streams fed by snow and rain that fall from the clouds cannot be salt.” “What you have just told us is very remarkable, Uncle,” observed Claire. “All water-courses, rivers, streams, torrents, brooks, come from and return to the sea.” “They come from the sea, an inexhaustible reservoir that covers with its waters a surface three times larger than that of all the continents joined together; from the sea, whose abysses go down at some places to the depth of 14 kilometers, and receive unceasingly the tribute of all the water-courses of the world, without ever being taxed beyond their capacity. The enormous surface of the sea furnishes the air with vapor which turns into clouds; later these clouds dissolve in rain and, chased by the wind, travel like immense watering-pots over the ground, rendering it fertile. In their turn, rain and snow, precipitated by the clouds, give birth to the rivers that carry their waters to the sea. In that way a continual current is effected which, starting from the sea, returns to the sea, after having traveled through the atmosphere in the form of clouds, watered the earth as rain, and crossed continents as rivers.