LIQUIDS AND THEIR PROPERTIES 



85 



The trolley cars of many cities are run, lighted, and warmed 

 by the energy of waterfalls in distant rivers. 



93. Springs and Wells. Since water seeks low places, 

 the rain which falls upon the earth flows c)own a slope, or 

 settles into the soil and finds its way lower still through 

 porous rocks or through cracks. When the water reaches a 

 layer of rock through which it cannot pass, it may follow 

 the rock to some place where the layer comes to the surface, 



FIG. 35. POWER FROM FALLING WATER 



Water flows from some height through the sluiceway into a bucket 

 on the water wheel. 1. Suppose that the buckets are empty and the wheel 

 is at rest; water enters the bucket nearest to s. What force sets the wheel 

 in motion? 2. Why does the wheel move faster when two buckets are filled? 

 3. Why is this form of bucket better than one with straight boards? 



perhaps many miles from where the water started. Many 

 hillside springs are formed in this way. 



A stratum of porous rock often contains much water. If 

 the rock is inclined, as in a hilly region, some parts of the 

 stratum are much lower than the source of the water. From 

 the lower levels, water rises through fissures, or cracks, to the 

 surface of the ground, by pressure of the water behind it. 

 Such springs are fissure springs. They bring water often 

 from a great distance as well as from a great depth. 



