EFFECTS OF THE MOVEMENTS OF WATER 35 



water from the rain and from the little streams that flow 

 in the hills. This place where the porous layer comes to 

 the surface is one thousand feet above sea-level. Now you 

 can see why water flows out of the top of such a well (see 

 Figs. 12 and 13). 



Much of the water that sinks into the ground is taken 

 up by the roots of plants, carried up into 'their leaves, and 

 there it evaporates. Evaporation from leaves is called 

 transpiration. Growing plants need to have water passing 

 constantly through them. Their bodies are chiefly com- 

 posed of water, and the water that moves through them 

 brings up from the soil substances that they need in their 

 growth. In the growing season thousands of pounds of 

 water transpire every day from an acre of trees. It has 

 been estimated that corn plants transpire about five thou- 

 sand pounds of water for every bushel of corn that they 

 produce. 



Topography means the form of the land. You have 

 learned that the work of water and the movements of the 

 earth's crust are the principal agents in determining the 

 nature of the topography. Upfoldings of the earth's crust 

 have formed the ranges of upland and mountains, and the 

 work of water has deepened the valleys and smoothed the 

 contours of the hills. Together, these great forces of nature 

 have formed the landscapes that to us are so beautiful. 

 We shall find them all the more beautiful and interesting 

 if we know something of the forces which have made them, 

 and something of the long history which lies behind them. 



Glaciers. You have noted the effects of running water. 

 But water in the form of ice has also had a great effect in 



