X. OUR FORESTS; THEIR USES AND THE NECESSITY 

 FOR THEIR PROTECTION 



XIX. Some uses of stems (.optional}. (Laboratory 

 Manual, Prob. X/X.) 

 (a) Special product from stems. 

 (ft) Some woods and their value. 

 (c} Field work in forestry. 



The Economic Value of Trees. Protection and Regulation of 

 Water Supply. Trees form a protective covering for the earth's 

 surface. They prevent soil from being washed away, and they hold 

 moisture in the ground. Without trees many of our rivers might 

 go dry in summer, while in the rainy season sudden floods would 

 result. The devastation of 

 immense areas in China and 

 considerable damage by 

 floods in parts of Switzer- 

 land, France, and in Penn- 

 sylvania has resulted where 

 the forest covering has been 

 removed. No one who has 

 tramped through our Adi- 

 rondack forest can escape 

 noticing the differences in 

 the condition of streams 

 which flow through areas 

 covered with forest and those from around which trees have 

 been cut. The latter streams often dry up entirely in hot 

 weather, while the forest-shaded stream has a never failing 

 supply of crystal water. 



The city of New York owes much of its importance to its posi- 

 tion at the mouth of a great river with a harbor large enough to 

 float the navies of the world. This river is supplied with water 



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rking to prevent erosion after the removal 

 of the forest in the French alps. 



