This section is from the book "Applied Science For Metal Workers", by William H. Dooley. Also available from Amazon: Applied Science For Metal Workers.
A river usually begins with a small stream in the hills and represents the drainage of the rain, ice, or snow that falls there. If there is a growth of trees on the hills, the roots of the trees tend to hold the water in the ground and prevent it from trickling down the slope rapidly. A lake usually has no outlet but is fed either by springs or by the drainage of the hills.
 
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