38 OF WATER. 



and parts with its moisture. The vesicles of vapor are 

 brought near each other, come together, and form drops 

 large and heavy enough to fall, and which cfome down as 

 rain. 



If air full of moisture be met by air much colder than 

 itself, the sudden cooling causes the water to be thrown 

 down, or precipitated, in torrents of rain. 



114. The cause of the fall of rain in a thunder shower 

 is thought to be the fact that electricity is always evolved 

 during evaporation, and that a cloud formed by evapora 

 tion must be therefore charged full of electricity. When 

 a cloud so charged meets another, or a mass of air, 

 charged with the other kind of electricity, the opposite 

 electricities rush together and unite in a lightning flash, 

 and the moisture held suspended by the action of elec 

 tricity is precipitated to the ground. 



115. When, during the formation of the rain drops, 

 the temperature of the air is below the freezing point, 

 the vesicles of moisture, or their fragments, are frozen 

 into little icy needles, which unite, at an angle of GO , 

 into beautiful, star-like flakes of Snow, and fall to the 

 ground. 



Snow has been called &quot; the poor man s manure.&quot; It 

 always brings down with it fertilizing substances ; and it 

 performs a most important office in many regions, by cov 

 ering over and protecting from extreme cold the surface 

 of the earth with all its clothing of plants, and keeping 

 in the warmth which had entered the earth during the 

 previous summer, and preventing its being radiated away 

 into empty space. 



11 C&amp;gt;. How Hail is formed is not perfectly well known. 

 Hail seems to be drops of rain frozen. Electricity lias 

 something to do with it, and in some parts of Europe, 



