SUB-SURFACE WATER 



315 



into springs; and part sinks deep into the soil and 

 rock. 



Which of these courses the greatest part of the rainfall 

 will take depends entirely upon the condition of its fall 

 and the kind of surface upon which it falls. If the rain- 

 fall comes down rapidly, 

 the larger part of it 

 will immediately run 

 off ; if it comes down 

 gently, much of it will 

 sink into the ground. 

 If it falls in forest re- 

 gions or where there is 

 much verdure, its flow 

 will be impeded by the 

 plants and roots. If 

 the surface upon which 

 it falls is hard-packed 

 and impervious, most of 

 it will run off, but if it 

 is loose and easily pene- 

 trated, much of it will 

 sink into the soil. Even 

 in the dry parched sands 

 of the desert, however, 



the rain falls sometimes in such cloud-burst torrents that 

 it runs off in rushing streams. 



151. Sub-Surface Water or Ground Water. The rain that 

 sinks into the ground descends slowly along the little 

 cracks or between the particles of soil until it reaches a 

 point where it can sink no further, or until it finds an 

 opening through which it can flow out to the surface at a 

 point lower than where it entered. Here it may ooze 

 slowly out, or it may be concentrated in a spring. 



FLOWING ARTESIAN WELL. 



