Science for beginners . s can usually see whether or not theywill rain, and what paths the showers will follow. 188. How Rain is Produced.—The fine water droplets of acumulus cloud float in the air like fog. The ascending aircurrents help to keep the droplets from falling. When enoughvapor has been condensed these droplets usually join togetherand settle downward faster than the rising air currents carrythem upward. They then begin to fall as rain. Rain dropsthat reach the ground range from very small up to % inchor more in diameter. You can measure their sizes by catchingsome rain in an inch
Science for beginners . s can usually see whether or not theywill rain, and what paths the showers will follow. 188. How Rain is Produced.—The fine water droplets of acumulus cloud float in the air like fog. The ascending aircurrents help to keep the droplets from falling. When enoughvapor has been condensed these droplets usually join togetherand settle downward faster than the rising air currents carrythem upward. They then begin to fall as rain. Rain dropsthat reach the ground range from very small up to % inchor more in diameter. You can measure their sizes by catchingsome rain in an inch or so of flour. The rain drops will form THE WATER VAPOR OF THE AIR 177 pellets in the flour. You can then put other water drops froma medicine dropper into the flour. Hold the dropper closeto a ruler and carefully measure the size of the water dropsbefore they fall. Then measure the flour pellets formed bythese drops. That will show whether the pellets are largeror smaller than the drops that made them, and how Fig. 135.—Types of snow crystals.(Photographed by Mr. W. A. Bentley.) Then you can measure formed by the rain, and findvery nearly the size of the rain drops. 189. Snow.—When the temperature in a cloud is belowfreezing, snow forms instead of rain. Snow flakes, when nottoo much broken by the wind, show many beautiful in Fig. 135 were caught on a board covered with dark 178 THE WEATHER cloth. The board was placed just outside a window so theflakes could be photographed through the glass. Many hun-dred different forms of snow flakes have been photographedby Mr. W. A. Bentley, of Jericho, Vt. Sleet. Either raindrops or partly melted snow flakes may fallthrough freezing air below the cloud and form pellets. If thesepellets rattle when they strike the ground or other objects, they arecalled sleet. Hail.—(See Thunderstorm, Art. 194). Soft Hail.—Soft hail is composed entirely of snow. The pelletsare usually small, but are sometimes a hal
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectscience, bookyear1921
