SPRINGS. WATER A SOLVENT. 39 



hail storms have been rendered much less frequent by 

 the use of lightning rods. 



117. Springs. The water which falls upon the earth 

 in rain, sinks into the ground and moistens it ; and, when 

 very abundant, penetrates deeper, till it meets with beds 

 of rock, or clay, or of some other impermeable earth, that 

 is, earth through which it cannot pass. It runs along 

 the surface of these beds until it meets a natural opening, 

 out of which it issues as a fountain or spring. Or, it may 

 remain in a basin, on the surface of the impermeable 

 bed, and be safe, as in a reservoir, until an artificial 

 outlet is made by digging a well. 



118. From springs run little rivulets, by the union 

 of many of which are formed brooks, rivers and lakes ; 

 the waters of all of which commonly flow at last into the 

 sea. There, the heat of the sun raises it in vapor to 

 begin again the beneficent circuit, and form mists and 

 clouds and rain. 



119. Water is essential to the life of every plant. Sev 

 eral of the substances on which plants feed, can penetrate 

 into their cells and thence through the tissues, only after 

 being dissolved in water. With it they are sucked in by 

 the roots, and in it are carried to the very extremities of 

 the plant. 



120. Next to heat, water is the most universal solvent. 

 The rain, as it descends, absorbs and condenses the 

 gases which float in the atmosphere, and brings them 

 down into the earth fit for the use of plants. Of 

 ammonia it can dissolve 780 times its own bulk ; of car 

 bonic acid, its own bulk ; and it commonly brings down a 

 portion of air, rich in oxygen, and sometimes nitric acid. 

 It also absorbs and brings down all kinds of dirt, and 

 other impurities, numerous minute seeds of plants, and 



