<div class="chaptext" id="l16"><SPAN name="less16"></SPAN>
<div class="lesson">LESSON XVI.</div>
<div class="chaphead">DEW, CLOUDS, AND RAIN.</div>
<p>The sun is all the time heating the water on the land and in the
sea, and changing it into vapor, which rises in the air. We cannot
see the vapor; but it is in the air around us.</p>
<p>If the vapor in the air is suddenly cooled, a strange thing
happens. Some of it quickly changes back into water. You have often
seen, in the early morning, little drops of water hanging like
pearls upon the blades of grass.</p>
<p>Now, where do these drops come from? They come from the air. The
vapor in the air floats against the cold grass and leaves, and is
cooled and changed into tiny drops of water. We call this
<i>dew</i>.</p>
<p>Of what use is dew?</p>
<p>If the night is quite cold, the dew will freeze. It is then called
frost. You have seen the frosty window pane with the beautiful
pictures upon it.</p>
<p>Make a picture of the window as you remember it, covered with the
pretty things made by the frost.</p>
<table summary="illustration" class="centeredimage" width="100" cellpadding="5"
cellspacing="0" border="0">
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<td><SPAN href="images/026_l.gif" target="_blank" id="ill26"><ANTIMG src=
"images/026.jpg" border="0" alt="WHEN VAPOR RISES HIGH IN THE COOL AIR." /></SPAN></td>
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<div class="caption">WHEN VAPOR RISES HIGH IN THE COOL AIR.</div>
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</table>
<p>When vapor rises high in the cool air it is turned into very small
drops of water or minute crystals of ice, and we can see it
floating about in the air. It is then called a <i>cloud</i>. Almost
any clear day you may see clouds form and then seem to melt
away.</p>
<p>You have seen on a blue sky, light, fleecy feather-clouds. They are
very high up, and it is very cold where they are. You have also
noticed the clouds at sunset with their beautiful colors. As the
sun sank lower and lower, how did they change, in shape and
color?</p>
<p>When clouds are low down, near the earth, we call them <i>fogs</i>
or <i>mist</i>.</p>
<p>If clouds are cooled, the little particles of water gather into
large drops and fall as <i>rain</i>. If the drops should freeze in
falling, we would call them <i>hail</i>.</p>
<p>What shape are the raindrops? Of what use is the rain?</p>
<table summary="illustration" class="centeredimage" width="100" cellpadding="5"
cellspacing="0" border="0">
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<td><SPAN href="images/027_l.gif" target="_blank" id="ill27"><ANTIMG src=
"images/027.jpg" border="0" alt="HAVE YOU EVER SEEN SNOWFLAKES THROUGH A MICROSCOPE?" /></SPAN></td>
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<div class="caption">HAVE YOU EVER SEEN SNOWFLAKES THROUGH A
MICROSCOPE?</div>
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</table>
<p>Sometimes, when it is very cold, the moisture in the air freezes
before it forms into drops, and falls in the beautiful flakes we
call <i>snow</i>. Have you ever seen snowflakes through a
microscope?</p>
<p>Snow keeps the roots of plants warm. Many plants would die in
winter if it were not for the snow. What other uses has snow?</p>
<p>Observe the clouds; fog, rain, snow, dew, frost, and tell what you
have noticed.</p>
<p><i>Write</i> what you have <i>seen</i> or <i>noticed</i> about
vapor, clouds, rain, etc.</p>
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