“Ah! now, papa, I think I understand what you mean. Yesterday the weather was very hot; and I suppose the mist which we noticed was produced in the same manner as steam is; only that it is the _sun’s_ heat which turns the particles of water into vapour. But, papa, what becomes of it all then? for if this watery vapour is lighter than the air, it would continue to rise till it had quite disappeared.” “When the string of your kite broke, Lewis, and it soared far away, for a short time, higher than it had ever been before, what do you suppose occasioned it to fall again?” Lewis thought for a moment, and then said, “Partly because I had no string to guide it, and partly, I suppose, papa, because the air above might be lighter, and not able to support its weight.” “Yes,” said his papa, “the atmosphere becomes less dense as it is more distant from the earth; so that the vapour, which the sun causes to exhale, rises until it reaches a region of its own weight; here it remains stationary for a time, till the accumulation of fresh vapours forms clouds, and these at length becoming too heavy for the air to support, descend in copious showers of rain, to refresh and fertilize the earth.” Lewis thought he could quite understand this. “But is this wonderful process,” he asked, “always going on? for, if so much rain and moisture falls upon the earth and sinks into it, does it not injure it? I should think the sun and wind would only dry the surface.” “Have you ever seen a spring?” asked Lewis’s father. Lewis said, he had seen several: there was the spring in the hill-side, which supplied the brook that ran at the bottom of his uncle’s garden; and the chalybeate-spring; and his papa had once shown them how the men, who were digging in a gravel-pit were troubled with the little springs, which kept rising out of the earth. They were obliged to work night and day, to pump the water out into slanting wooden troughs, by which means it was carried down to the river. “And the brook at the bottom of the garden,” said Helen, “runs into the same river. I have often watched it, winding through the green meadows, till it joined the broad stream of the Lea.” “But, Helen,” asked Mr. Ashton, “is this little stream always flowing?”