These are only a few of the things of interest that you can see for yourself by studying the air. Watch the sky; it is full of interest. See what you can observe for yourself. Watch especially the clouds, for they are not only interesting but beautiful (Fig. 17). Their forms are often graceful, and they change with such rapidity that you can notice it as you watch them. Even in the daytime the colors and shadows are beautiful; but at sunrise and at sunset the clouds are often changed to gorgeous banks of color. [Illustration: _Fig. 17. A sky flecked with clouds high in the air._] Watch the clouds and you will be repaid; look especially for the great piles of clouds in the east during the summer when the sun is setting (Fig. 18). Those lofty banks, tinged with silver and gold, and rising like mountains thousands of feet into the air, are really made of bits of fog and mist. Among them vapor is still changing to water and rain drops are forming, while violent currents are whirling the drops about, and perhaps lifting them to such a height that they are being frozen into hailstones. Far off to the east, beneath that cloud, rain is falling in torrents, lightning is flashing and thunder crashing, though you cannot hear it because it is so far away. [Illustration: _Fig. 18. The cloud banks of a thunder storm on the horizon._] You see the storm merely as a brightly lighted and beautifully colored cloud mass in the sky; but the people over whom it is hanging find it a threatening black cloud, the source of a furious wind, a heavy rain, and the awe-inspiring lightning. To them it may not be beautiful, though grand in the extreme; and so, too, when the summer thunder shower visits you in the early evening, you may know that people to the west of you are probably looking at its side and top and admiring its beauty of form and color. The storm passes on, still to the eastward, and finally the cloud mass entirely disappears beneath the eastern horizon; but if you watch, you will see signs that it is still there, though out of sight; for in the darkness of the night you can see the eastern horizon lighted by little flashes, the source of which cannot be seen. You call it "heat lightning," but it is really the last signal that we can see of the vanishing thunder storm, so far away that the sound of the crashing thunder cannot be heard. You watch the mysterious flashes; they grow dimmer and dimmer and finally you see them no more. Our summer shower is gone. It has done what thousands of others have done before, and what thousands of others will do in the future. It has started, moved off, and finally disappeared from sight; and as it has gone it has told us a story. You can read a part of this story if you will; and in reading it will find much that interests. LEAFLET VII. A SNOW STORM.[9] BY ANNA BOTSFORD COMSTOCK.