110 OUTLINES OF FORESTRY. 



1. Surface drainage, or where the rain-water 

 runs directly off the surface. 



2. Underground drainage, or where the rain- 

 water first sinks into the ground and then dis- 

 charges as springs into some stream that empties 

 into a river. 



Surface drainage, for the greater part, takes 

 place rapidly, and occurs mainly during the time 

 rain is falling. It practically stops a few hours 

 after the rain ceases. 



Underground drainage takes place slowly, and 

 may continue for many weeks after the rain ceases. 



All the water in a river comes from the rain that 

 falls on the earth's surface. The rivers continue 

 to flow because the springs are continually empty- 

 ing their waters into the rivers, and, before they 

 run dry, more rain falls and keeps up the supply 

 in their reservoirs. 



Some rivers are larger than others. This is 

 because : 



1. More rain falls on those parts of the earth 

 through which they flow. 



2. The land which slopes towards such rivers 

 covers a greater part of the earth's surface. 



The water runs off the earth from a higher to a 

 lower level, because water runs down hill. The 



