Science for beginners . Fig. 132.—Large cumulus, partly hidden. The dark clouds across itsfront are rather low clouds much nearer the camera. Note the bril-liantly lighted top. The sharp, clean-cut outline above shows that norain has developed in the portions Fig. 133.—Strato-cumulus, lower surface. Note the uneven dark spots are sometimes caused by the greater thickness of thecloud at those spots; sometimes by the shadows of higher clouds fallingupon the strato-cumulus layer. THE WATER VAPOR OF THE AIR 175 masses of warm air with masses of cold air; sometimes in win-ter,
Science for beginners . Fig. 132.—Large cumulus, partly hidden. The dark clouds across itsfront are rather low clouds much nearer the camera. Note the bril-liantly lighted top. The sharp, clean-cut outline above shows that norain has developed in the portions Fig. 133.—Strato-cumulus, lower surface. Note the uneven dark spots are sometimes caused by the greater thickness of thecloud at those spots; sometimes by the shadows of higher clouds fallingupon the strato-cumulus layer. THE WATER VAPOR OF THE AIR 175 masses of warm air with masses of cold air; sometimes in win-ter, by warm damp winds blowing over a colder region. 185. The Forming of Clouds.—The lowest clouds and allthe denser clouds are like fog. Clouds are formed by the con-densing of water vapor in the air. They are interesting andoften beautiful. Clouds are the messengers of the air. Some-times they tell us of sunny days to come; often they warn usof approaching storms. What they tell depends on how muchone knows of them. The foregoing six pages introduce clouds and show howto study them for yourself. Figure 127 shows the principal classes of clouds, arrangedaccording to their height. The accompanying table gives thechief divisions and a number of their combinatio
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectscience, bookyear1921
